Plant hormones
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Nitrate, NO and ROS Signaling in Stem Cell Homeostasis

Nitrate, NO and ROS Signaling in Stem Cell Homeostasis | Plant hormones | Scoop.it
Authors: Aakanksha Wany, Christine H. Foyer and Kapuganti Jagadis Gupta.

Trends in Plant Science (2018)

Excerpt: "Shoot and root growth is facilitated by stem cells in the shoot and root apical meristems (SAM and RAM). Recent reports have demonstrated a close link between nitrogen nutrition, nitric oxide (NO), and reactive oxygen species (ROS) in the regulation of SAM and RAM functions in response to nitrogen availability. The shoot and root apical meristems (SAM and RAM) contain a group of proliferating stem cells, which play an important role in organogenesis. Several hormones and other signaling molecules fulfil important functions in SAM and RAM regulation. A recent study has demonstrated that SAM activity responds to soil nitrate availability through the expression of WUSCHEL (WUS), which is a key regulator of stem cell homeostasis [1]. Nitrate sensing pathways regulate cytokinin precursors, which function as long-range signals to modulate WUS expression and control SAM homeostasis. However, nitrate-dependent signaling is likely to be more complex than can be explained solely in terms of cytokinin signaling. Given the demonstrated roles of nitric oxide (NO) and reactive oxygen species (ROS) in stem cell functions [2], these crucial redox signals may fulfil key roles in the regulation of SAM activity responses to soil nitrate availability."
Julio Retamales's insight:
A commentary and critical review on the article by Landrein et al.("Nitrate modulates stem cell dynamics in Arabidopsis shoot meristems through cytokinins") published in PNAS and to be found at:

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Control of Fruit Tree Vigor Induced by Dwarfing Rootstocks - Chapter

Control of Fruit Tree Vigor Induced by Dwarfing Rootstocks - Chapter | Plant hormones | Scoop.it
Authors: Boris Basile and Theodore M. DeJong.

Horticultural Reviews (2019)

Abstract: "Grafting of fruit trees has been practiced for more than two millennia, and dwarfing rootstocks have been used to control scion vigor for several centuries. The fact that most commercial temperate fruit trees are compound plants composed of two separate genotypes (the scion selected for fruit and shoot characteristics, and the rootstock selected for root characteristics) makes them interesting objects for studying root–shoot interactions in plants. The size‐controlling effect of certain rootstocks in various fruit tree species is perhaps the most intriguing and commercially important example of how genetics of one part (the root) of compound plants can influence the behavior of the other part (the shoot). While there is no debate about the potential of rootstocks to affect the growth and productivity of the scion in compound fruit trees, there is no consensus on the physiological and/or anatomical mechanisms involved in the dwarfing phenomenon. Indeed, different hypotheses focusing on various aspects of plant function have been proposed to explain the dwarfing mechanism. This review discusses the concepts and the experimental support for six of the primary theories proposed to explain the dwarfing mechanism induced by rootstocks in fruit trees. These theories are based on the idea that dwarfing is caused by semi‐incompatibility between the rootstock and scion or anatomical, morphological, or physiological characteristics of the rootstock or graft union that affect tree water relations, tree nutrition, scion–rootstock hormonal and metabolic signaling, carbohydrate storage and mobilization, and/or the relative abilities of the scion and rootstock components of the tree to compete for resources. Each of the proposed theories has received some experimentally based support in selected crops. Scion–rootstock semi‐incompatibility is a general mechanism that may be involved in many scion–rootstock combinations and could cause responses that appear to involve the factors common to the other theories. None of the theories have been documented to be involved in all rootstock–scion combinations or to be solely responsible for the dwarfing response of scions associated with specific rootstocks. However, there is good evidence that changes in water relations are related to the dwarfing response in several species. In retrospect, it is perhaps unrealistic to think that any single one of these or other mechanisms could be solely responsible for orchestrating all of the complex interactions involved in rootstock‐induced vigor reduction of the scion. 
Julio Retamales's insight:
Chapter 2 in Horticultural Reviews, Volumen 46, edited by Ian Warrington.
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Molecular role of cytokinin in bud activation and outgrowth in apple branching based on transcriptomic analysis

Molecular role of cytokinin in bud activation and outgrowth in apple branching based on transcriptomic analysis | Plant hormones | Scoop.it

Authors: Guofang Li, Ming Tan, Fang Cheng, Xiaojie Liu, Siyan Qi, Hongfei Chen, Dong Zhang, Caiping Zhao, Mingyu Han and Juanjuan Ma.


Molecular Plant Biology (2018)


Key message: Axillary bud activation and outgrowth were dependent on local cytokinin, and that bud activation preceded the activation of cell cycle and cell growth genes in apple branching.


Abstract: "Cytokinin is often applied to apple trees to produce more shoot branches in apple seedlings. The molecular response of apple to the application of cytokinin, and the relationship between bud activation and cell cycle in apple branching, however, are poorly understood. In this study, RNA sequencing was used to characterize differential expression genes in axillary buds of 1-year grafted “Fuji” apple at 4 and 96 h after cytokinin application. And comparative gene expression analyses were performed in buds of decapitated shoots and buds of the treatment of biosynthetic inhibitor of cytokinin (Lovastatin) on decapitated shoots. Results indicated that decapitation and cytokinin increased ZR content in buds and internodes at 4–8 h, and induced bud elongation at 96 h after treatment, relative to buds in shoots receiving the Lovastatin treatment. RNA-seq analysis indicated that differential expression genes in auxin and cytokinin signal transduction were significantly enriched at 4 h, and DNA replication was enriched at 96 h. Cytokinin-responsive type-A response regulator, auxin polar transport, and axillary meristem-related genes were up-regulated at 4 h in the cytokinin and decapitation treatments, while qRT-PCR analysis showed that cell cycle and cell growth genes were up-regulated after 8 h. Collectively, the data indicated that bud activation and outgrowth might be dependent on local cytokinin synthesis in axillary buds or stems, and that bud activation preceded the activation of cell cycle genes during the outgrowth of ABs in apple shoots."

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Auxins and Cytokinins—The Role of Subcellular Organization on Homeostasis - Review

Auxins and Cytokinins—The Role of Subcellular Organization on Homeostasis - Review | Plant hormones | Scoop.it

Authors: Vladimír Skalický, Martin Kubeš, Richard Napier and Ondřej Novák.


International Journal of Molecular Sciences (2018)


Abstract: "Plant hormones are master regulators of plant growth and development. Better knowledge of their spatial signaling and homeostasis (transport and metabolism) on the lowest structural levels (cellular and subcellular) is therefore crucial to a better understanding of developmental processes in plants. Recent progress in phytohormone analysis at the cellular and subcellular levels has greatly improved the effectiveness of isolation protocols and the sensitivity of analytical methods. This review is mainly focused on homeostasis of two plant hormone groups, auxins and cytokinins. It will summarize and discuss their tissue- and cell-type specific distributions at the cellular and subcellular levels."

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Elucidation of the mechanism of reflowering in tree peony (Paeonia suffruticosa) ‘Zi Luo Lan’ by defoliation and gibberellic acid application

Elucidation of the mechanism of reflowering in tree peony (Paeonia suffruticosa) ‘Zi Luo Lan’ by defoliation and gibberellic acid application | Plant hormones | Scoop.it
Authors: Jingqi Xue, Tingting Li, Shunli Wang, Yuqian Xue, Fengrong Hu and Xiuxin Zhang.

Plant Physiology and Biochemistry (2018)

Highlights: • Autumn-flowering treatment (defoliation + GA3) induces tree peony reflowering in autumn. • Autumn-flowering treatment promotes nutrient absorption in buds as release from dormancy. • Autumn-flowering treatment simultaneously increases GA3 and decreases ABA levels. • High ratios of GA3/ABA may play a key role in inducing tree peony reflowering. • Reflowering is likely due to the inhibition of ABA function.

Abstract: "In this study, the reflowering mechanism of tree peony (Paeonia suffruticosa ‘Zi Luo Lan’) after defoliation and gibberellic acid (GA) application (autumn-flowering treatment) was investigated by monitoring the morphological changes, measuring the endogenous GA3 and abscisic acid (ABA) contents, and determining the expression patterns of six GA- and two ABA-related genes. The results show that autumn-flowering treatment induced tree peony reflowering in autumn, which was accompanied by nutrient absorption in buds. The application of exogenous GA3 induced a simultaneous increase in GA3 and decrease in ABA levels, suggesting that the high ratios of GA3/ABA may play a key role in inducing tree peony reflowering. RT-qPCR analysis shows that PsCPS and PsGA2ox were significantly induced and inhibited by GA3 application, respectively, which supports the hypothesis that GA3 treatment induces endogenous GA3 production. In addition, GA3 treatment inhibited the expression of the PsGID1c, but its effect on PsGAI1 was limited, whereas the expression of PsGAMYB could be GA- or ABA-related. Furthermore, autumn-flowering treatment significantly inhibited the expression of PsNCED and PsbZIP, which coincides with the observed changes in ABA levels. Therefore, we postulate that autumn-flowering treatment induces tree peony reflowering by inhibiting the function of ABA accumulation and signaling."
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Expression of genes in the potential regulatory pathways controlling alternate bearing in ‘Fuji’ (Malus domestica Borkh.) apple trees during flower induction

Expression of genes in the potential regulatory pathways controlling alternate bearing in ‘Fuji’ (Malus domestica Borkh.) apple trees during flower induction | Plant hormones | Scoop.it
Authors: Xiya Zuo, Dong Zhang, Shixiang Wang, Libo Xing, Youmei Li, Sheng Fan, Lizhi Zhang, Juanjuan Ma, Caiping Zhao, Kamran Shah, Na An and Mingyu Han.

Plant Physiology and Biochemistry (2018)

Highlights: • The flowering rate in terminal buds of short shoots in OFF year ‘Nagafu No. 2’ trees was significantly lower than ON trees. • A total of 1027 DEGs were identified that were involved in secondary metabolism, sugar metabolism and plant hormone pathways. • Sugar contents and hormone levels in the ON and OFF trees were analyzed. • Expression profiling of sugar -related, hormone-related, and floral genes in ON- and OFF-year buds were analyzed. • A hypothetical model for the regulation of the alternate bearing phenotype based on the current results was put forward.

Abstract: "Most perennial fruit trees have an alternate bearing problem where a heavy fruit load is produced one year (ON year) but few flowers and fruits produced the next year (OFF year), resulting in a significant fluctuation in production. In the present study, comparative transcriptome analysis of terminal buds of apple (Malus domestica Borkh., cv. Nagafu No. 2) trees was conducted during the floral induction period in the ON and OFF years to identify the potential regulatory pathways controlling alternate bearing. A total of 1027 differentially expressed genes (DEGs), most of which were involved in secondary metabolism, sugar metabolism, plant hormone pathways, were identified. The analysis focused on differences in sugar content and hormone levels between the ON and OFF trees. Sucrose content, zeatin-riboside (ZR), and abscisic acid (ABA) levels were lower in ON-year buds than in OFF-year buds. ON buds also had elevated levels of gibberellins (GAs), with a higher expression of GA20 oxidase (GA20ox) and a significant lower level of RGA-like2 (RGL2). Expression analyses also revealed a significantly higher level of SQUAMOSA-PROMOTER BINDING PROTEIN-LIKE genes (MdSPL1, MdSPL6 and MdSPL12) transcripts levels in buds of OFF trees at 45 days after full bloom (DAFB). LEAFY (LFY) expression increased significantly prior to flower induction in OFF buds. These findings provide new information of the role of hormones in alternate bearing, as well as other processes, and provide new insights into the molecular mechanisms regulating alternate bearing in perennial fruit trees."
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Defense‐related priming and responses to recurring drought: two manifestations of plant transcriptional memory mediated by the ABA and JA signaling pathways - Review

Defense‐related priming and responses to recurring drought: two manifestations of plant transcriptional memory mediated by the ABA and JA signaling pathways - Review | Plant hormones | Scoop.it
Author: Zoya Avramova.

Plant, Cell & Environment (2018)

Abstract: "Collective evidence from agricultural practices and from scientific research has demonstrated that plants can alter their phenotypic responses to repeated biotic and abiotic stresses or their elicitors. A coordinated reaction at the organismal, cellular and genome levels have suggested that plants can “remember” an earlier stress and modify their future responses, accordingly. Stress memory may increase a plant's survival chances by improving its tolerance/avoidance abilities and may provide a mechanism for acclimation and adaptation. Understanding the mechanisms that regulate plant stress memory is not only an intellectually challenging topic but has important implications for agricultural practices as well. Here, I focus exclusively on specific aspects of the transcription memory in response to recurring dehydration stresses and the memory‐type responses to insect damage in a process known as ‘priming’. The questions discussed are: 1) whether/how the two memory phenomena are connected at the level of transcriptional regulation; 2) how differential transcription is achieved mechanistically under a repeated stress; 3) whether similar molecular and/or epigenetic mechanisms are involved. Possible biological relevance of transcriptional stress memory and its preservation in plant evolution are also discussed."
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Phytohormones Regulate the Development of Arbuscular Mycorrhizal Symbiosis - Review

Phytohormones Regulate the Development of Arbuscular Mycorrhizal Symbiosis - Review | Plant hormones | Scoop.it

Authors: Dehua Liao, Shuangshuang Wang, Miaomiao Cui, Jinhui Liu, Aiqun Chen and Guohua Xu.


International Journal of Molecular Sciences (2018)


Abstract: "Most terrestrial plants are able to form a root symbiosis with arbuscular mycorrhizal (AM) fungi for enhancing the assimilation of mineral nutrients. AM fungi are obligate symbionts that depend on host plants as their sole carbon source. Development of an AM association requires a continuous signal exchange between the two symbionts, which triggers coordinated differentiation of both partners, to enable their interaction within the root cells. The control of the AM symbiosis involves a finely-tuned process, and an increasing number of studies have pointed to a pivotal role of several phytohormones, such as strigolactones (SLs), gibberellic acids (GAs), and auxin, in the modulation of AM symbiosis, through the early recognition of events up to the final arbuscular formation. SLs are involved in the presymbiotic growth of the fungus, while auxin is required for both the early steps of fungal growth and the differentiation of arbuscules. GAs modulate arbuscule formation in a dose-dependent manner, via DELLA proteins, a group of GRAS transcription factors that negatively control the GA signaling. Here, we summarize the recent findings on the roles of these plant hormones in AM symbiosis, and also explore the current understanding of how the DELLA proteins act as central regulators to coordinate plant hormone signaling, to regulate the AM symbiosis."

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The XV Collection: Auxin Transport — more a River Delta than a Stream

The XV Collection: Auxin Transport — more a River Delta than a Stream | Plant hormones | Scoop.it

Author: Mark Estelle 


PLOS Biologue Blog (2018)


Excerpt: "The sessile lifestyle of plants is enabled by remarkable developmental plasticity. Plant form is affected by a wide range of environmental conditions from nutrient availability to herbivory, so two plants with the same genotype can appear quite different, depending on their environment. All plant organs and tissues are derived from dispersed stem cell populations called meristems. Individual meristems can act independently to a certain extent but are also controlled by systemic signals that coordinate and integrate their activities. The identity of these signals and how they function, has long been a subject of intense interest to plant biologists. The article that I chose to highlight for the PLOS Biology XV Collection is by Tom Bennett, Ottoline Leyser and colleagues and provides important new insight into the nature of systemic communication."

Julio Retamales's insight:
Commentary on the article by Bennett et al. published in 2016 in PLOS Biology ("Connective Auxin Transport in the Shoot Facilitates Communication between Shoot Apices"). The original article is related to Leyser's talk posted here and is to be found at:

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Abscisic and Jasmonic Acids Contribute to Soybean Tolerance to the Soybean Aphid (Aphis glycines Matsumura)

Abscisic and Jasmonic Acids Contribute to Soybean Tolerance to the Soybean Aphid (Aphis glycines Matsumura) | Plant hormones | Scoop.it

Authors: Kaitlin M. Chapman, Lia Marchi-Werle, Thomas E. Hunt, Tiffany M. Heng-Moss and Joe Louis.


Scientific Reports (2018)


Abstract: "Plant resistance can provide effective, economical, and sustainable pest control. Tolerance to the soybean aphid has been identified and confirmed in the soybean KS4202. Although its resistance mechanisms are not fully understood, evidence suggests that enhanced detoxification of reactive oxygen species (ROS) is an active system under high aphid infestation. We further explored tolerance by evaluating the differences in constitutive and aphid-induced defenses in KS4202 through the expression of selected defense-related transcripts and the levels of the phytohormones abscisic acid (ABA), jasmonic acid (JA), JA-isoleucine (JA-Ile), cis-(+)-12-oxo-phytodienoic acid (OPDA), and salicylic acid (SA) over several time points. Higher constitutive levels of ABA and JA, and basal expression of ABA- and JA-related transcripts were found in the tolerant genotype. Conversely, aphid-induced defenses in KS4202 were expressed as an upregulation of peroxidases under prolonged aphid infestation (>7 days). Our results point at the importance of phytohormones in constitutive defense in KS4202 tolerance to the soybean aphid. Understanding the underlying mechanisms of tolerance will assist breeding for soybean with these traits, and perhaps help extend the durability of Rag (Resistance to Aphis glycines)-mediated resistance genes."

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A transportome-scale amiRNA-based screen identifies redundant roles of Arabidopsis ABCB6 and ABCB20 in auxin transport

A transportome-scale amiRNA-based screen identifies redundant roles of Arabidopsis ABCB6 and ABCB20 in auxin transport | Plant hormones | Scoop.it

Authors: Yuqin Zhang, Victoria Nasser, Odelia Pisanty, Moutasem Omary, Nikolai Wulff, Martin Di Donato, Iris Tal, Felix Hauser, Pengchao Hao, Ohad Roth, Hillel Fromm, Julian I. Schroeder, Markus Geisler, Hussam Hassan Nour-Eldin and Eilon Shani.


Nature Communications (2018)


Editor's view: Characterizing plant membrane transporters via genetic methods is complicated by functional redundancy among multi-gene transporter families. Here Zhang et al. use an artificial microRNA-based screen to overcome this issue and show that ABCB6 and ABCB20 act redundantly to regulate auxin transport.


Abstract: "Transport of signaling molecules is of major importance for regulating plant growth, development, and responses to the environment. A prime example is the spatial-distribution of auxin, which is regulated via transporters to govern developmental patterning. A critical limitation in our ability to identify transporters by forward genetic screens is their potential functional redundancy. Here, we overcome part of this functional redundancy via a transportome, multi-targeted forward-genetic screen using artificial-microRNAs (amiRNAs). We generate a library of 3000 plant lines expressing 1777 amiRNAs, designed to target closely homologous genes within subclades of transporter families and identify, genotype and quantitatively phenotype, 80 lines showing reproducible shoot growth phenotypes. Within this population, we discover and characterize a strong redundant role for the unstudied ABCB6 and ABCB20 genes in auxin transport and response. The unique multi-targeted lines generated in this study could serve as a genetic resource that is expected to reveal additional transporters."

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β-cyclocitral is a conserved root growth regulator - Preprint

β-cyclocitral is a conserved root growth regulator - Preprint | Plant hormones | Scoop.it

Authors: Alexandra J. Dickinson, Kevin Lehner, Jianing Mi, Kun-Peng Jia, Medhavinee Mijar, Jose Dinneny, Salim Al-Babili and Philip N. Benfey.


bioRxiv (2018)


Abstract: "Natural compounds capable of increasing root depth and branching are desirable tools for enhancing stress tolerance in crops. We devised a sensitized screen to identify natural metabolites capable of regulating root traits in Arabidopsis. β-cyclocitral, an endogenous root compound, was found to promote cell divisions in root meristems and stimulate lateral root branching. β-cyclocitral rescued meristematic cell divisions in ccd1ccd4 biosynthesis mutants and β-cyclocitral-driven root growth was found to be independent of auxin, brassinosteroid, and ROS signaling pathways. β-cyclocitral had a conserved effect on root growth in tomato and rice and generated significantly more compact crown root systems in rice. Moreover, β-cyclocitral treatment enhanced plant vigor in rice plants exposed to salt-contaminated soil. These results indicate that β-cyclocitral is a broadly effective root growth promoter in both monocots and eudicots and could be a valuable tool to enhance crop vigor under environmental stress."


One Sentence Summary: β-cyclocitral is a metabolite of β-carotene that was identified using a sensitized chemical screen and acts broadly across plants to enhance root growth and branching.

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Transcriptional profiling reveals that a MYB transcription factor MsMYB4 contributes to the salinity stress response of alfalfa

Transcriptional profiling reveals that a MYB transcription factor MsMYB4 contributes to the salinity stress response of alfalfa | Plant hormones | Scoop.it

Authors: Wei Dong, Xijiang Liu, Donglei Li, Tianxue Gao and Yuguang Song.


PLoS ONE (2018)


Abstract: "MYB transcription factors are important regulators of the plant response to abiotic stress. Their participation in the salinity stress of the key forage legume species alfalfa (Medicago sativa) was investigated here by comparing the transcriptomes of the two cultivars Dryland (DL) and Sundory (SD), which differed with respect to their ability to tolerate salinity stress. When challenged by the stress, DL plants were better able than SD ones to scavenge reactive oxygen species. A large number of genes encoding transcription regulators, signal transducers and proteins involved in both primary and secondary metabolism were differentially transcribed in the two cultivars, especially when plants were subjected to salinity stress. The set of induced genes included 17 MYB family of transcription factors, all of which were subsequently isolated. The effect of constitutively expressing these genes on the salinity tolerance expressed by Arabidopsis thaliana was investigated. The introduction of MsMYB4 significantly increased the plants’ salinity tolerance in an abscisic acid-dependent manner. A sub-cellular localization experiment and a transactivation assay indicated that MsMYB4 was deposited in the nucleus and was able to activate transcription in yeast. Based on this information, we propose that the MsMYB4 products is likely directly involved in alfalfa’s response to salinity stress."

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Fruit Thinning - Advances and Trends - Chapter

Fruit Thinning - Advances and Trends - Chapter | Plant hormones | Scoop.it
Authors: Guglielmo Costa, Alessandro Botton and Giannina Vizzotto.

Horticultural Reviews (2019)

Abstract: "In modern horticulture, fruit thinning must be performed to fulfill market demands. Although several advances in knowledge have been achieved in this field, the fruit industry is continuously evolving in terms of technical, economic, and environmental sustainability. In facing these changes, research does not always satisfy in a timely manner the strong demands from the productive sector. Fruit thinning remains an unpredictable cultural technique that may result in either over‐ or underthinning. For this reason, modeling tools based on research advances into early fruit abscission physiology may be useful for setting up decision support systems (DSSs) aimed at improving thinning performance. However, the fruitlet abscission process leading to cell separation at the level of the abscission zone involves multiple changes in cell structure, metabolism, and gene expression, making this research sector extremely challenging and complex. Ongoing climate change further increases this complexity, thus requiring more intensive and dynamic efforts that need to be coordinated at a higher level within an international R&D platform. With this perspective, a structural funding policy must be pursued not only by institutional agencies but also by the whole productive chain."
Julio Retamales's insight:
Chapter 4 in Horticultural Reviews, Volumen 46, edited by Ian Warrington. Aspects of hormonal regulation of fruit abscission are discussed.
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Identification of Auxin Activity Like 1, a chemical with weak functions in auxin signaling pathway

Identification of Auxin Activity Like 1, a chemical with weak functions in auxin signaling pathway | Plant hormones | Scoop.it

Authors: Wenbo Li, Haimin Li, Peng Xu, Zhi Xie, Yajin Ye, Lingting Li, Deqiang Li, Yijing Zhang, Laigeng Li and Yang Zhao.


Plant Molecular Biology (2018)


Key message: A new synthetic auxin AAL1 with new structure was identified. Different from known auxins, it has weak effects. By AAL1, we found specific amino acids could restore the effects of auxin with similar structure. 


Abstract: "Auxin, one of the most important phytohormones, plays crucial roles in plant growth, development and environmental response. Although many critical regulators have been identified in auxin signaling pathway, some factors, especially those with weak fine-tuning roles, are still yet to be discovered. Through chemical genetic screenings, we identified a small molecule, Auxin Activity Like 1 (AAL1), which can effectively inhibit dark-grown Arabidopsis thaliana seedlings. Genetic screening identified AAL1 resistant mutants are also hyposensitive to indole-3-acetic acid (IAA) and 2,4-dichlorophenoxyacetic acid (2,4-D). AAL1 resistant mutants such as shy2-3c and ecr1-2 are well characterized as mutants in auxin signaling pathway. Genetic studies showed that AAL1 functions through auxin receptor Transport Inhibitor Response1 (TIR1) and its functions depend on auxin influx and efflux carriers. Compared with known auxins, AAL1 exhibits relatively weak effects on plant growth, with 20 µM and 50 µM IC50 (half growth inhibition chemical concentration) in root and hypocotyl growth respectively. Interestingly, we found the inhibitory effects of AAL1 and IAA could be partially restored by tyrosine and tryptophan respectively, suggesting some amino acids can also affect auxin signaling pathway in a moderate manner. Taken together, our results demonstrate that AAL1 acts through auxin signaling pathway, and AAL1, as a weak auxin activity analog, provides us a tool to study weak genetic interactions in auxin pathway."

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Characterization of and genetic variation for tomato seed thermo-inhibition and thermo-dormancy

Characterization of and genetic variation for tomato seed thermo-inhibition and thermo-dormancy | Plant hormones | Scoop.it

Authors: Nafiseh Geshnizjani, Farshid Ghaderi-Far, Leo A. J. Willems, Henk W. M. Hilhorst and Wilco Ligterink.


BMC Plant Biology (2018)


Abstract: "Exposing imbibed seeds to high temperatures may lead to either thermo-inhibition of germination or thermo-dormancy responses. In thermo-inhibition, seed germination is inhibited but quickly resumed when temperatures are lowered. Upon prolonged exposure to elevated temperatures, thermo-dormancy may be induced and seeds are not able to germinate even at optimal temperatures. In order to explore underlying physiological and molecular aspects of thermo-induced secondary dormancy, we have investigated the physiological responses of tomato seeds to elevated temperatures and the molecular mechanisms that could explain the performance of tomato seeds at elevated temperature. In order to investigate how tomato seeds respond to high temperature we used two distinct tomato accessions: Solanum lycopersicum (cv. Moneymaker) (MM) and Solanum pimpinellifolium accession CGN14498 (PI). MM seeds did not germinate under high temperature conditions while seeds of PI reached a maximum germination of 80%. Despite the high germination percentage of PI, germinated seeds did not produce healthy seedling at 37 °C. By using a candidate gene approach we have tested if similar molecular pathways (abscisic acid (ABA) and gibberellic acid (GA)) present in lettuce and Arabidopsis, are regulating thermo-inhibition and thermo-dormancy responses in tomato. We showed that the ABA biosynthesis pathway genes NCED1 and NCED9 were upregulated whereas two of the GA-biosynthesis regulators (GA3ox1 and GA20ox1) were downregulated in tomato thermo-dormant seeds at elevated temperature. To identify novel regulators of tomato seed performance under high temperature, we screened a Recombinant Inbred Line (RIL) population derived from a cross between the two tomato accessions MM and PI for thermo-inhibition and dormancy induction. Several QTLs were detected, particularly for thermo-dormancy, which may be caused by new regulators of thermo-inhibition and thermo-dormancy in tomato. None of the genes studied in this research were co-locating with the detected QTLs. The new QTLs discovered in this study will therefore be useful to further elucidate the molecular mechanisms underlying the responses of tomato seeds to high temperature and eventually lead to identification of the causal genes regulating these responses."

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Transporters and Mechanisms of Hormone Transport in Arabidopsis - Chapter

Transporters and Mechanisms of Hormone Transport in Arabidopsis - Chapter | Plant hormones | Scoop.it
Authors: Rashed Abualia, Eva Benkova and Benoît Lacombe.

Advances in Botanical Research (2018)

Abstract: "Plant hormones as signalling molecules play an essential role in the control of plant growth and development. Typically, sites of hormonal action are usually distant from the site of biosynthesis thus relying on efficient transport mechanisms. Over the last decades, molecular identification of proteins and protein complexes involved in hormonal transport has started. Advanced screens for genes involved in hormonal transport in combination with transport assays using heterologous systems such as yeast, insect, or tobacco BY2 cells or Xenopus oocytes provided important insights into mechanisms underlying distribution of hormones in plant body and led to identification of principal transporters for each hormone. This review gives a short overview of the mechanisms of hormonal transport and transporters identified in Arabidopsis thaliana."
Julio Retamales's insight:
Relevant review on hormone transport in this chapter in press. Only parts of the figure are shown.
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Possible interaction of ROS, antioxidants and ABA to survive osmotic stress upon acclimation in Vigna radiata L. Wilczek seedlings

Possible interaction of ROS, antioxidants and ABA to survive osmotic stress upon acclimation in Vigna radiata L. Wilczek seedlings | Plant hormones | Scoop.it
Authors: Moumita Sahu and Rup Kumar Kar.

Plant Physiology and Biochemistry (2018)

Highlights: • Acclimation to water stress was associated with increased production of and enhanced sensitivity to ABA. • ABA signaling occurs through ROS as reflected in the enhanced production of extracellular O2·ˉ and H2O2 under water stress. • ROS signaling help in ameliorating stress via elevated activities of antioxidative enzymes to control the oxidative burst.

Abstract: "Acclimation is a process of adjustment to gradual environmental change that enables plants to survive further stress by triggering some tolerance mechanism possibly involving ABA, ROS and oxidative metabolism. Here we have studied acclimation responses in terms of the performances with regard to physiological (growth and relative water content) and biochemical (chlorophyll, carotenoids, protein, malondialdehyde, sugar content) attributes, ABA production and stomatal sensitivity to exogenous ABA, extracellular ROS production and activation of antioxidant system. Our study reveals that repeated exposure to short-term mild water stress simulated by polyethylene glycol (PEG-6000) induces acclimation in mung bean (Vigna radiata L. Wilczek) seedlings. Acclimation induced tolerance was associated with reduced leaf size and enhanced root growth, accumulation of soluble sugar as osmoprotectant, maintenance of water potential, lessening of membrane damage as indicated by lower MDA content. Acclimated mung bean seedlings have shown greater degree of tolerance through increased production of and enhanced sensitivity to ABA (as reflected by faster stomatal closure), enhanced production of extracellular O2.- and H2O2 and the elevated activities of antioxidative enzymes to control the oxidative burst. Taken together, the results convey that acclimated seedlings minimize osmotic stress-induced damage through a possible network of ABA, ROS and antioxidants."
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Systems, variation, individuality and plant hormones - Review

Systems, variation, individuality and plant hormones - Review | Plant hormones | Scoop.it
Authors: Masaaki Watahiki and Anthony Trewavas.

Progress in Biophysics and Molecular Biology (2018)

Abstract: "Inter-individual variation in plants and particularly in hormone content, figures strongly in evolution and behaviour. Homo sapiens and Arabidopsis exhibit similar and substantial phenotypic and molecular variation. Whereas there is a very substantial degree of hormone variation in mankind, reports of inter-individual variation in plant hormone content are virtually absent but are likely to be as large if not larger than that in mankind. Reasons for this absence are discussed. Using an example of inter-individual variation in ethylene content in ripening, the article shows how biological time is compressed by hormones. It further resolves an old issue of very wide hormone dose response that result directly from negative regulation in hormone (and light) transduction. Negative regulation is used because of inter-individual variability in hormone synthesis, receptors and ancillary proteins, a consequence of substantial genomic and environmental variation. Somatic mosaics have been reported for several plant tissues and these too contribute to tissue variation and wide variation in hormone response. The article concludes by examining what variation exists in gravitropic responses. There are multiple sensing systems of gravity vectors and multiple routes towards curvature. These are an aspect of the need for reliability in both inter-individual variation and unpredictable environments. Plant hormone inter-individuality is a new area for research and is likely to change appreciation of the mechanisms that underpin individual behaviour."
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Short Panicle 3 controls panicle architecture by upregulating APO2/RFL and increasing cytokinin content in rice

Short Panicle 3 controls panicle architecture by upregulating APO2/RFL and increasing cytokinin content in rice | Plant hormones | Scoop.it
Authors: Yong Huang, Xufeng Bai, Meifang Luo and Yongzhong Xing.

Journal of Integrative Plant Biology (2018)

Abstract: "Inflorescence architecture is a major determinant of spikelet numbers per panicle, a key component of grain yield in rice. In this study, Short Panicle 3 (SP3) was identified from a short panicle 3 (sp3) mutant in which T‐DNA was inserted in the promoter of SP3, resulting in a knockdown mutation. SP3 encodes a DNA binding with one finger (Dof) transcriptional activator. Quantitative real time (qRT)‐PCR and RNA in situ hybridization assays confirmed that SP3 is preferentially expressed in the young rice inflorescence, specifically in the branch primordial regions. SP3 acts as a negative regulator of inflorescence meristem abortion by upregulating APO2/RFL. SP3 both up‐ and down‐regulates expression of genes involved in cytokinin biosynthesis and catabolism, respectively. Consequently, cytokinin concentrations are decreased in young sp3 panicles, thereby leading to small panicles having fewer branches and spikelets. Our findings support a model in which SP3 regulates panicle architecture by modulating cytokinin homeostasis. Potential applications to rice breeding, through gene‐editing of the SP3 promoter are assessed."
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Genetic interactions between ABA signalling and the Arg/N-end rule pathway during Arabidopsis seedling establishment

Genetic interactions between ABA signalling and the Arg/N-end rule pathway during Arabidopsis seedling establishment | Plant hormones | Scoop.it

Authors: Hongtao Zhang, Lucy Gannon, Peter D. Jones, Chelsea A. Rundle, Kirsty L. Hassall, Daniel J. Gibbs, Michael J. Holdsworth and Frederica L. Theodoulou.


Scientific Reports (2018)


Abstract: "The Arg/N-end rule pathway of ubiquitin-mediated proteolysis has multiple functions throughout plant development, notably in the transition from dormant seed to photoautotrophic seedling. PROTEOLYSIS6 (PRT6), an N-recognin E3 ligase of the Arg/N-end rule regulates the degradation of transcription factor substrates belonging to Group VII of the Ethylene Response Factor superfamily (ERFVIIs). It is not known whether ERFVIIs are associated with all known functions of the Arg/N-end rule, and the downstream pathways influenced by ERFVIIs are not fully defined. Here, we examined the relationship between PRT6 function, ERFVIIs and ABA signalling in Arabidopsis seedling establishment. Physiological analysis of seedlings revealed that N-end rule-regulated stabilisation of three of the five ERFVIIs, RAP2.12, RAP2.2 and RAP2.3, controls sugar sensitivity of seedling establishment and oil body breakdown following germination. ABA signalling components ABA INSENSITIVE (ABI)4 as well as ABI3 and ABI5 were found to enhance ABA sensitivity of germination and sugar sensitivity of establishment in a background containing stabilised ERFVIIs. However, N-end rule regulation of oil bodies was not dependent on canonical ABA signalling. We propose that the N-end rule serves to control multiple aspects of the seed to seedling transition by regulation of ERFVII activity, involving both ABA-dependent and independent signalling pathways."

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Rice transcription factor OsMADS25 modulates root growth and confers salinity tolerance via the ABA–mediated regulatory pathway and ROS scavenging

Rice transcription factor OsMADS25 modulates root growth and confers salinity tolerance via the ABA–mediated regulatory pathway and ROS scavenging | Plant hormones | Scoop.it

Authors: Ning Xu, Yanli Chu, Hongli Chen, Xingxing Li, Qi Wu, Liang Jin, Guixue Wang and Junli Huang


PLoS Genetics (2018)


Abstract: "Plant roots are constantly exposed to a variety of abiotic stresses, and high salinity is one of the major limiting conditions that impose constraints on plant growth. In this study, we describe that OsMADS25 is required for the root growth as well as salinity tolerance, via maintaining ROS homeostasis in rice (Oryza sativa). Overexpression of OsMADS25 remarkably enhanced the primary root (PR) length and lateral root (LR) density, whereas RNAi silence of this gene reduced PR elongation significantly, with altered ROS accumulation in the root tip. Transcriptional activation assays indicated that OsMADS25 activates OsGST4 (glutathione S–transferase) expression directly by binding to its promoter. Meanwhile, osgst4 mutant exhibited repressed growth and high sensitivity to salinity and oxidative stress, and recombinant OsGST4 protein was found to have ROS–scavenging activity in vitro. Expectedly, overexpression of OsMADS25 significantly enhanced the tolerance to salinity and oxidative stress in rice plants, with the elevated activity of antioxidant enzymes, increased accumulation of osmoprotective solute proline and reduced frequency of open stoma. Furthermore, OsMADS25 specifically activated the transcription of OsP5CR, a key component of proline biosynthesis, by binding to its promoter. Interestingly, overexpression of OsMADS25 raised the root sensitivity to exogenous ABA, and the expression of ABA–dependent stress–responsive genes was elevated greatly in overexpression plants under salinity stress. In addition, OsMADS25 seemed to promote auxin signaling by activating OsYUC4 transcription. Taken together, our findings reveal that OsMADS25 might be an important transcriptional regulator that regulates the root growth and confers salinity tolerance in rice via the ABA–mediated regulatory pathway and ROS scavenging."

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Transcriptome analysis of the genes regulating phytohormone and cellular patterning in Lagerstroemia plant architecture

Transcriptome analysis of the genes regulating phytohormone and cellular patterning in Lagerstroemia plant architecture | Plant hormones | Scoop.it

Authors: Yiqian Ju, Lu Feng, Jiyang Wu, Yuanjun Ye, Tangchun Zheng, Ming Cai, Tangren Cheng, Jia Wang, Qixiang Zhang and Huitang Pan


Scientific Reports (2018)


Abstract: "Plant architecture is a popular research topic because plants with different growth habits that may generate economic or ornamental value are in great demand by orchards and nurseries. However, the molecular basis of the architecture of woody perennial plants is poorly understood due to the complexity of the phenotypic and regulatory relationships. Here, transcriptional profiling of dwarf and non-dwarf crapemyrtles was performed, and potential target genes were identified based on the phenotype, histology and phytohormone metabolite levels. An integrated analysis demonstrated that the internode length was explained mainly by cell number and secondarily by cell length and revealed important hormones in regulatory pathway of Lagerstroemia architecture. Differentially expressed genes (DEGs) involved in phytohormone pathways and cellular patterning regulation were analysed, and the regulatory relationships between these parameters were evaluated at the transcriptional level. Exogenous indole-3-acetic acid (IAA) and gibberellin A4 (GA4) treatments further indicated the pivotal role of auxin in cell division within the shoot apical meristem (SAM) and suggested an interaction between auxin and GA4 in regulating the internode length of Lagerstroemia. These results provide insights for further functional genomic studies on the regulatory mechanisms underlying Lagerstroemia plant architecture and may improve the efficiency of woody plant molecular breeding."

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OsJAZ9 overexpression improves potassium deficiency tolerance in rice by modulating jasmonic acid levels and signaling - Preprint

OsJAZ9 overexpression improves potassium deficiency tolerance in rice by modulating jasmonic acid levels and signaling - Preprint | Plant hormones | Scoop.it

Authors: Ajit Pal Singh, Bipin Kumar Pandey, Poonam Mehra, Ravindra Kumar Chandan, Gopaljee Jha and Jitender Giri.


bioRxiv (2018)


Abstract: "Potassium (K) which makes around 2-10% of plants total dry biomass, when become deficient, makes the plants highly susceptible to both abiotic and biotic stresses. Recent evidences suggest overlapping transcriptional responses to K deficiency and Jasmonate (JA) treatment in plants. However, a link between these responses was missing. Notably, K deficiency and JA application produce similar phenotypic and transcriptional responses. Here, we used molecular, physiological and morphological studies to analyze the role of OsJAZ9 in JA homeostasis, K deficiency and sheath blight resistance. We raised OsJAZ9 overexpression, knockdown, translational reporter and C-terminal deleted translational reporter lines in rice to establish the role of JA signaling in K ion homeostasis and OsJAZ9 as a critical component of JA signaling for K deficiency response. OsJAZ9 overexpression and knockdown provide K deficiency tolerance and sensitivity, respectively, by modulating various K transporters and root system architecture. Furthermore, RNA Seq and JA profiling revealed an elevation of JA responsive genes and JA levels in OsJAZ9 OE lines under K deficiency. Our data provide clear evidence on the crucial role of JAZ repressor, OsJAZ9 in improving K deficiency tolerance in rice by altering JA levels and signaling."

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Acetoin and 2,3-butanediol from Bacillus amyloliquefaciens induce stomatal closure in Arabidopsis thaliana and Nicotiana benthamiana 

Acetoin and 2,3-butanediol from Bacillus amyloliquefaciens induce stomatal closure in Arabidopsis thaliana and Nicotiana benthamiana  | Plant hormones | Scoop.it

Authors: Liming Wu, Xi Li, Liumin Ma, Rainer Borriss, Zhen Wu and Xuewen Gao.


Journal of Experimental Botany (2018)


Editor's view: Acetoin and 2,3-butanediol from Bacillus amyloliquefaciens absorbed through the roots induce stomatal closure in Arabidopsis and tobacco via the salicylic and abscisic acid signaling pathways.


Abstract: "Plants live in close association with large communities of microbes, some of which are foliar pathogens that invade tissues, primarily via stomata on the leaf surface. Stomata are considered part of an integral, innate immunity system capable of efficiently preventing pathogens from entering the host plant. Although Bacillus, a typical plant growth-promoting rhizobacterium, is known to induce stomatal closure, the substances participating in this closure and the mechanism involved in its regulation remain poorly understood. Here, we screened a mutant library and conducted site-specific mutagenesis experiments in order to identify such substances. We found that acetoin and 2,3-butanediol from B. amyloliquefaciens FZB42 induced stomatal closure in Arabidopsis thaliana and Nicotiana benthamiana. These two components could function either via root absorption or volatilization to restrict stomatal apertures, but root absorption was more efficient. Both substances invoked the salicylic acid and abscisic acid signaling pathways to close the stomata and stimulated accumulation of hydrogen peroxide and nitric oxide. The results present comprehensive evidence of how soil rhizobacteria may affect plant stomata, in a way that reinforces the evolved mutualism between the two groups of organisms, and provide potential alternative avenues of research towards reducing the incidence of disease in crops."

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