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Authors: Gwendolyn K. Kirschner, Frank Hochholdinger, Silvio Salvi, Malcolm J. Bennett, Guoqiang Huang and Rahul A. Bhosale.
Trends in Plant Science (2024)
Highlights: The root angle in cereals determines soil resource capture, stress resilience, and yield, especially in suboptimal conditions. Root angle regulation involves competing gravitropic and antigravitropic offset mechanisms. Understanding the mechanisms underlying root angle regulation in cereals is important due to their complex root system made up of distinct root types, formed at different stages of development. Recent studies in cereals revealed genes regulating the root angle. However, the precise mechanisms determining and maintaining root angle in distinct root types remain unclear. Understanding the molecular mechanisms underlying root angle control is essential for incorporating the root angle trait into breeding programs.
Abstract: "The root angle plays a critical role in efficiently capturing nutrients and water from different soil layers. Steeper root angles enable access to mobile water and nitrogen from deeper soil layers, whereas shallow root angles facilitate the capture of immobile phosphorus from the topsoil. Thus, understanding the genetic regulation of the root angle is crucial for breeding crop varieties that can efficiently capture resources and enhance yield. Moreover, this understanding can contribute to developing varieties that effectively sequester carbon in deeper soil layers, supporting global carbon mitigation efforts. Here we review and consolidate significant recent discoveries regarding the molecular components controlling root angle in cereal crop species and outline the remaining research gaps in this field."
Authors: Carly M. Shanks, Karin Rothkegel, Matthew D Brooks, Chia-Yi Cheng, José M. Alvarez, Sandrine Ruffel, Gabriel Krouk, Rodrigo A Gutiérrez and Gloria M. Coruzzi.
The Plant Cell (2024)
Abstract: "A plant’s response to external and internal nitrogen signals/status relies on sensing and signaling mechanisms that operate across spatial and temporal dimensions. From a comprehensive systems biology perspective, this involves integrating nitrogen responses in different cell types and over long distances to ensure organ coordination in real time and yield practical applications. In this prospective review, we focus on novel aspects of nitrogen (N) sensing/signaling uncovered using temporal and spatial systems biology approaches, largely in the model Arabidopsis. The temporal aspects span: transcriptional responses to N-dose mediated by Michaelis-Menten kinetics; the role of the master NLP7 transcription factor as a nitrate sensor, its nitrate-dependent TF nuclear retention, its “hit-and-run” mode of target gene regulation and temporal transcriptional cascade identified by “Network Walking”. Spatial aspects of N-sensing/signaling have been uncovered in cell type-specific studies in roots and in root-to-shoot communication. We explore new approaches using single cell sequencing data, trajectory inference and pseudotime analysis as well as machine learning and artificial intelligence approaches. Finally, unveiling the mechanisms underlying the spatial dynamics of nitrogen sensing/signaling networks across species from model-to-crop could pave the way for translational studies to improve nitrogen-use efficiency in crops. Such outcomes could potentially reduce the detrimental effects of excessive fertilizer usage on groundwater pollution and greenhouse gas emissions."
Authors: Sonali Roy, Ivone Torres-Jerez, Shulan Zhang, Wei Liu, Katharina Schiessl, Divya Jain, Clarissa Boschiero, Hee-Kyung Lee, Nicholas Krom, Patrick X. Zhao, Jeremy D. Murray, Giles E. D. Oldroyd, Wolf-Rüdiger Scheible and Michael Udvardi.
The Plant Journal (2024)
Significance Statement: Nodule positioning is an understudied trait, yet it determines the length of the root that can support nodule formation and consequently the total number of functional nodules formed. We identify genetic factors called GOLVEN peptides that alter nodule and lateral root positioning on the primary root along with several other traits including nodule organ initiation and root architecture.
Abstract: "The conservation of GOLVEN (GLV)/ROOT MERISTEM GROWTH FACTOR (RGF) peptide encoding genes across plant genomes capable of forming roots or root-like structures underscores their potential significance in the terrestrial adaptation of plants. This study investigates the function and role of GOLVEN peptide-coding genes in Medicago truncatula. Five out of fifteen GLV/RGF genes were notably upregulated during nodule organogenesis and were differentially responsive to nitrogen deficiency and auxin treatment. Specifically, the expression of MtGLV9 and MtGLV10 at nodule initiation sites was contingent upon the NODULE INCEPTION transcription factor. Overexpression of these five nodule-induced GLV genes in hairy roots of M. truncatula and application of their synthetic peptide analogues led to a decrease in nodule count by 25–50%. Uniquely, the GOLVEN10 peptide altered the positioning of the first formed lateral root and nodule on the primary root axis, an observation we term ‘noduletaxis’; this decreased the length of the lateral organ formation zone on roots. Histological section of roots treated with synthetic GOLVEN10 peptide revealed an increased cell number within the root cortical cell layers without a corresponding increase in cell length, leading to an elongation of the root likely introducing a spatiotemporal delay in organ formation. At the transcription level, the GOLVEN10 peptide suppressed expression of microtubule-related genes and exerted its effects by changing expression of a large subset of Auxin responsive genes. These findings advance our understanding of the molecular mechanisms by which GOLVEN peptides modulate root morphology, nodule ontogeny, and interactions with key transcriptional pathways."
Authors: Dandan Hu, Ruifan Cui, Ke Wang, Yuming Yang, Ruiyang Wang, Hongqing Zhu, Mengshi He, Yukun Fan, Le Wang, Li Wang, Shanshan Chu, Jinyu Zhang, Shanshan Zhang, Yifei Yang, Xuhao Zhai, Haiyan Lv, Dandan Zhang, Jinshe Wang, Fanjiang Kong, Deyue Yu, Hengyou Zhang and Dan Zhang.
The Plant Cell (2024)
One-sentence summary: The major quantitative trait locus gene GmGDPD2 controls root and phosphorus efficiency traits and interacts with Myb73 and GA2ox1 to enhance yield traits.
Abstract: "Phosphorus is indispensable in agricultural production. An increasing food supply requires more efficient use of phosphate due to limited phosphate resources. However, how crops regulate phosphate efficiency remains largely unknown. Here, we identified a major quantitative trait locus, qPE19, that controls seven low-phosphate (LP)-related traits in soybean (Glycine max) through linkage mapping and genome-wide association studies. We identified the gene responsible for qPE19 as GLYCEROPHOSPHORYL DIESTER PHOSPHODIESTERASE2 (GmGDPD2), and haplotype 5 represents the optimal allele favoring LP tolerance. Overexpression of GmGDPD2 significantly affects hormone signaling and improves root architecture, phosphate efficiency and yield-related traits; conversely, CRISPR/Cas9-edited plants show decreases in these traits. GmMyb73 negatively regulates GmGDPD2 by directly binding to its promoter, thus GmMyb73 negatively regulates LP tolerance. GmGDPD2 physically interacts with GA 2-oxidase 1 (GmGA2ox1) in the plasma membrane, and overexpressing GmGA2ox1 enhances LP-associated traits, similar to GmGDPD2 overexpression. Analysis of double mutants for GmGDPD2 and GmGA2ox1 demonstrated that GmGDPD2 regulates LP tolerance likely by influencing auxin and gibberellin dose-associated cell division in root. These results reveal a regulatory module that plays a major role in regulating LP tolerance in soybean and is expected to be utilized to develop phosphate-efficient varieties to enhance soybean production, particularly in phosphate-deficient soils.
Authors: Javier A. Miret, Cara A. Griffiths and Matthew J. Paul.
Journal of Plant Physiology (2024)
Abstract: "Sugar homeostasis is a critical feature of biological systems. In humans, raised and dysregulated blood sugar is a serious health issue. In plants, directed changes in sucrose homeostasis and allocation represent opportunities in crop improvement. Plant tissue sucrose varies more than blood glucose and is found at higher concentrations (cytosol and phloem ca. 100 mM v 3.9–6.9 mM for blood glucose). Tissue sucrose varies with developmental stage and environment, but cytosol and phloem exhibit tight sucrose control. Sucrose homeostasis is a consequence of the integration of photosynthesis, synthesis of storage end-products such as starch, transport of sucrose to sinks and sink metabolism. Trehalose 6-phosphate (T6P)-SnRK1 and TOR play central, still emerging roles in regulating and coordinating these processes. Overall, tissue sucrose levels are more strongly related to growth than to photosynthesis. As a key sucrose signal, T6P regulates sucrose levels, transport and metabolic pathways to coordinate source and sink at a whole plant level. Emerging evidence shows that T6P interacts with meristems. With careful targeting, T6P manipulation through exploiting natural variation, chemical intervention and genetic modification is delivering benefits for crop yields. Regulation of cereal grain set, filling and retention may be the most strategically important aspect of sucrose allocation and homeostasis for food security."
Authors: Chao Tan, Suxin Li, Jia Song, Xianfu Zheng, Hao Zheng, Weichang Xu, Cui Wan, Tan Zhang, Qiang Bian and Shuzhen Men.
Communications Biology (2024)
Editor's view: Physiological and molecular studies have shown that 3,4-dichlorophenylacetic acid (Dcaa) has auxin-like activity and acts through the auxin signaling pathway in plants. This provides a basis for the application of Dcaa in agricultural practice.
Abstract: "Auxins and their analogs are widely used to promote root growth, flower and fruit development, and yield in crops. The action characteristics and application scope of various auxins are different. To overcome the limitations of existing auxins, expand the scope of applications, and reduce side effects, it is necessary to screen new auxin analogs. Here, we identified 3,4-dichlorophenylacetic acid (Dcaa) as having auxin-like activity and acting through the auxin signaling pathway in plants. At the physiological level, Dcaa promotes the elongation of oat coleoptile segments, the generation of adventitious roots, and the growth of crop roots. At the molecular level, Dcaa induces the expression of auxin-responsive genes and acts through auxin receptors. Molecular docking results showed that Dcaa can bind to auxin receptors, among which TIR1 has the highest binding activity. Application of Dcaa at the root tip of the DR5:GUS auxin-responsive reporter induces GUS expression in the root hair zone, which requires the PIN2 auxin efflux carrier. Dcaa also inhibits the endocytosis of PIN proteins like other auxins. These results provide a basis for the application of Dcaa in agricultural practices."
Authors: Ru-Feng Song, Xiao-Yu Hu, Wen-Cheng Liu and Hong-Mei Yuan.
Plant Cell Reports (2024)
Key message ABI5 functions in ABA-mediated anthocyanin accumulation in plant response to low phosphate.
Abstract: "Low phosphate (LP)-induced anthocyanin biosynthesis and accumulation play an important role in plant adaptive response to phosphate starvation conditions. However, whether and how the stress phytohormone abscisic acid (ABA) participates in LP-induced anthocyanin accumulation remain elusive. Here, we report that ABA is required for LP-induced anthocyanin accumulation in Arabidopsis thaliana. Disrupting ABA DEFICIENT2 (ABA2), a key ABA-biosynthetic gene, or BETA-GLUCOSIDASE1 (BG1), a major gene implicated in converting conjugated ABA to active ABA, significantly impairs LP-induced anthocyanin accumulation, as LP-induced expression of the anthocyanin-biosynthetic genes Chalcone Synthase (CHS) is dampened in the aba2 and bg1 mutant. In addition, LP-induced anthocyanin accumulation is defective in the mutants of ABA signaling pathway, including ABA receptors, ABA Insensitive2, and the transcription factors ABA Insensitive5 (ABI5), suggesting a role of ABI5 in ABA-mediated upregulation of anthocyanin-biosynthetic genes in plant response to LP. Indeed, LP-induced expression of CHS is repressed in the abi5-7 mutant but further promoted in the ABI5-overexpressing plants compared to the wild-type. Moreover, ABI5 can bind to and transcriptionally activate CHS, and the defectiveness of LP-induced anthocyanin accumulation in abi5-7 can be restored by overexpressing CHS. Collectively, our findings illustrates that ABI5 functions in ABA-mediated LP-induced anthocyanin accumulation in Arabidopsis."
Authors: Yuqing He, Yao Zhao, Jitao Hu, Lanlan Wang, Linying Li, Xueying Zhang, Zhongjing Zhou, Lili Chen, Hua Wang, Jiaoyu Wang and Gaojie Hong.
Molecular Plant (2024)
Abstract: "The growth-promoting hormones brassinosteroids (BRs) and their key signaling component BZR1 play a vital role in balancing normal growth and defense reactions. Here, we discovered that BRs and OsBZR1 upregulated sakuranetin accumulation and conferred basal defense against Magnaporthe oryzae infection under normal conditions. Resource shortages, including phosphate (Pi) deficiency, potentially disrupt this growth–defense balance. OsSPX1 and OsSPX2 have been reported to sense Pi concentration and interact with the Pi signal mediator OsPHR2, thus regulating Pi starvation responses. In this study, we discovered that OsSPX1/2 interacts with OsBZR1 in both Pi-sufficient and Pi-deficient conditions, inhibiting BR-responsive genes. When Pi is sufficient, OsSPX1/2 is captured by OsPHR2, enabling most of OsBZR1 to promote plant growth and maintain basal resistance. In response to Pi starvation, more OsSPX1/2 is released from OsPHR2 to inhibit OsBZR1 activity, resulting in slower growth. Collectively, our study reveals that the OsBZR1–SPX1/2 module balances the plant growth–immunity trade-off in response to Pi availability."
Authors: Tak Lee, Martina Orvosova, Morgane Batzenschlager, Marcelo Bueno Batista, Paul C. Bailey, Nadia A. Mohd-Radzman, Aram Gurzadyan, Naomi Stuer, Kirankumar S. Mysore, Jiangqi Wen, Thomas Ott, Giles E.D. Oldroyd and Katharina Schiessl.
Current Biology (2024)
Editor's view: To host N-fixing bacteria, legumes grow root nodules initiated via a lateral root program. Lee et al. show that two LSH transcription factors mediate the divergence between lateral roots and nodules by promoting the proliferation of colonizable cells. LSH1/LSH2 regulate the nodule identity genes NF-YA1 and NOOT1/NOOT2 and auxin/cytokinin dynamics.
Highlights: • LSHs are key regulators of symbiotic root nodule differentiation downstream of NIN • LSHs promote cell divisions in the root cortex that support bacterial colonization • LSHs promote expression of the nodule organ identity genes NOOT1/NOOT2 and NF-YA1 • LSHs repress PLETHORA root regulators and modulate auxin-cytokinin dynamics
Abstract: "Legumes produce specialized root nodules that are distinct from lateral roots in morphology and function, with nodules intracellularly hosting nitrogen-fixing bacteria. We have previously shown that a lateral root program underpins nodule initiation, but there must be additional developmental regulators that confer nodule identity. Here, we show two members of the LIGHT-SENSITIVE SHORT HYPOCOTYL (LSH) transcription factor family, predominantly known to define shoot meristem complexity and organ boundaries, function as regulators of nodule organ identity. In parallel to the root initiation program, LSH1/LSH2 recruit a program into the root cortex that mediates the divergence into nodules, in particular with cell divisions in the mid-cortex. This includes regulation of auxin and cytokinin, promotion of NODULE ROOT1/2 and Nuclear Factor YA1, and suppression of the lateral root program. A principal outcome of LSH1/LSH2 function is the production of cells able to accommodate nitrogen-fixing bacteria, a key feature unique to nodules."
Authors: Hirotomo Takatsuka, Toshiki Amari and Masaaki Umeda.
Plant Signaling & Behavior (2024)
Abstract: "Root hair, single-celled tubular structures originating from the epidermis, plays a vital role in the uptake of nutrients from the soil by increasing the root surface area. Therefore, optimizing root hair growth is crucial for plants to survive in fluctuating environments. Root hair length is determined by the action of various plant hormones, among which the roles of auxin and ethylene have been extensively studied. However, evidence for the involvement of cytokinins has remained elusive. We recently reported that the cytokinin-activated B-type response regulators, ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) and ARR12 directly upregulate the expression of ROOT HAIR DEFECTIVE 6-LIKE 4 (RSL4), which encodes a key transcription factor that controls root hair elongation. However, depending on the nutrient availability, it is unknown whether the ARR1/12–RSL4 pathway controls root hair elongation. This study shows that phosphate deficiency induced the expression of RSL4 and increased the root hair length through ARR1/12, though the transcript and protein levels of ARR1/12 did not change. These results indicate that cytokinins, together with other hormones, regulate root hair growth under phosphate starvation conditions."
Authors: Andrea Genre, Serena Capitanio and Paola Bonfante.
In Book: Fungal Associations (2024)
Abstract: "Mycorrhizas are mutualistic interactions that the majority of land plants establish with a heterogeneous group of soil fungi; their distribution and diversity have supported the success of plants on the planet. Among all different types of mycorrhizas, arbuscular mycorrhiza (AM) is the most ancient and the most common in host plants of all major crops. The functional core of AM is a finely branched fungal structure called the arbuscule. Arbuscules are hosted inside living root cells, within a specialized cell compartment that is generated through a precise sequence of molecular and cellular events. Over the last 10 years, the application of novel technologies, such as genome sequencing, high-throughput transcriptomics, and live cell imaging, has generated substantial advances in our knowledge of such events. Here, we present a synopsis of the recent literature on the interactions between AM fungi and their hosts, with an evolutionary-developmental focus on the intimate contact that develops between plant cells and fungal hyphae, in terms of molecular signaling, nutrient exchange, and cell organization."
Authors: Hayet Houmani and Francisco J. Corpas.
Plant Physiology and Biochemistry (2024)
Highlights • Mineral nutrients are determinant factors for plant growth and development. • Some minerals have signaling properties and can mediate a stress response. • Nutrients such as Ca2+, K+, N, or Fe interact with other signaling molecules (hormones, NO, H2O2 or H2S) to exert their signaling function.
Abstract: "Plant cells are in constant communication to coordinate development processes and environmental reactions. Under stressful conditions, such communication allows the plant cells to adjust their activities and development. This is due to intercellular signaling events which involve several components. In plant development, cell-to-cell signaling is ensured by mobile signals hormones, hydrogen peroxide (H2O2), nitric oxide (NO), or hydrogen sulfide (H2S), as well as several transcription factors and small RNAs. Mineral nutrients, including macro and microelements, are determinant factors for plant growth and development and are, currently, recognized as potential signal molecules. This review aims to highlight the role of nutrients, particularly calcium, potassium, magnesium, nitrogen, phosphorus, and iron as signaling components with special attention to the mechanism of response against stress conditions."
Authors: Mariel C. Isidra-Arellano, Jawahar Singh and Oswaldo Valdés-López.
Trends in Plant Science (2024)
Abstract: "Strigolactones (SLs) are fundamental to the ability of plants to cope with phosphate deficiency. A recent study by Yuan et al. indicates that the genetic module PHR2/NSP1/NSP2 is crucial in activating SL biosynthesis and signaling under inorganic phosphate (Pi) deficiency. Furthermore, this genetic module is essential for improving Pi and nitrogen homeostasis in rice."
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Authors: Silvia Quaggiotti, Leonardo Buzzicotti, Karen E. Koch, Jiahn Chou Guan, Sara Trevisan, Serena Varotto, Benedetto Ruperti and Laura Ravazzolo.
Plant and Soil (2024)
Abstract: "Background and Aims - Nitrogen (N) is an essential macronutrient that can limit plant development and crop yield through widespread physiological and molecular impacts. In maize, N-starvation enhances biosynthesis and exudation of strigolactones (SLs) in a process reversible by nitrate addition and consequent repression of genes for SL biosynthesis. Methods - In the present study, a maize mutant deficient in SL biosynthesis (zmccd8) allowed an in-depth analysis of SL contributions under low N. Both hydroponic and field conditions were used to better characterize the response of the mutant to N availability. Results - The severity of responses to N-limitation by the SL-deficient zmccd8 mutant extended from growth parameters to content of iron, sulfur, protein, and photosynthetic pigments, as well as pronounced impacts on expression of key genes, which could be crucial molecular target for the SL-mediated acclimatation to N shortage. Conclusions - Our results demonstrate that SLs are critical for physiological acclimation to N deficiency by maize and identify central players in this action. Further contributions by iron and sulfur are implicated in the complex pathway underlying SL modulation of responses to N-deprivation, thus widening our knowledge on SL functioning and providing new hints on their potential use in agriculture."
Authors: Long Lu, Xinyu Chen, Qinyan Tan, Wenqian Li, Yanyan Sun, Zaoli Zhang, Yuanyuan Song and Rensen Zeng.
Plants (2024)
Abstract: "Aluminum toxicity poses a significant constraint on crop production in acidic soils. While phytohormones are recognized for their pivotal role in mediating plant responses to aluminum stress, the specific involvement of gibberellin (GA) in regulating aluminum tolerance remains unexplored. In this study, we demonstrate that external GA exacerbates the inhibitory impact of aluminum stress on root growth of rice seedlings, concurrently promoting reactive oxygen species (ROS) accumulation. Furthermore, rice plants overexpressing the GA synthesis gene SD1 exhibit enhanced sensitivity to aluminum stress. In contrast, the slr1 gain-of-function mutant, characterized by impeded GA signaling, displays enhanced tolerance to aluminum stress, suggesting the negative regulatory role of GA in rice resistance to aluminum-induced toxicity. We also reveal that GA application suppresses the expression of crucial aluminum tolerance genes in rice, including Al resistance transcription factor 1 (ART1), Nramp aluminum transporter 1 (OsNramp4), and Sensitive to Aluminum 1 (SAL1). Conversely, the slr1 mutant exhibits up-regulated expression of these genes compared to the wild type. In summary, our results shed light on the inhibitory effect of GA in rice resistance to aluminum stress, contributing to a theoretical foundation for unraveling the intricate mechanisms of plant hormones in regulating aluminum tolerance."
Authors: Wendell J. Pereira, Jade Boyd, Daniel Conde, Paolo M. Triozzi, Kelly M. Balmant, Christopher Dervinis, Henry W. Schmidt, Carolina Boaventura-Novaes, Sanhita Chakraborty, Sara A. Knaack, Yueyao Gao, Frank Alexander Feltus, Sushmita Roy, Jean-Michel Ané, Julia Frugoli and Matias Kirst.
Cell Reports (2024)
Editor's view: Plant nitrogen fixation by rhizobia is agriculture’s most important symbiotic association, but only a few species develop root nodules to house the bacteria. Using single-cell analysis, Pereira et al. dissect the transcriptional program necessary for nodule formation, an essential step for the future introduction of this symbiotic relationship into crops.
Highlights: • Single-cell sequencing of a Medicago mutant captures rare cell response to rhizobia • Root hair and stele cells differentiate to support infection and nodulation • Cortex-derived cellular lineages modulate phytohormone activity in their trajectory • High-dimension gene regulatory network analysis identifies RNS regulators
Abstract: "Legumes establish a symbiotic relationship with nitrogen-fixing rhizobia by developing nodules. Nodules are modified lateral roots that undergo changes in their cellular development in response to bacteria, but the transcriptional reprogramming that occurs in these root cells remains largely uncharacterized. Here, we describe the cell-type-specific transcriptome response of Medicago truncatula roots to rhizobia during early nodule development in the wild-type genotype Jemalong A17, complemented with a hypernodulating mutant (sunn-4) to expand the cell population responding to infection and subsequent biological inferences. The analysis identifies epidermal root hair and stele sub-cell types associated with a symbiotic response to infection and regulation of nodule proliferation. Trajectory inference shows cortex-derived cell lineages differentiating to form the nodule primordia and, posteriorly, its meristem, while modulating the regulation of phytohormone-related genes. Gene regulatory analysis of the cell transcriptomes identifies new regulators of nodulation, including STYLISH 4, for which the function is validated."
Authors: Peter R. Ryan and Jianli Yang.
Cell Research (2024)
Summary: "Plant cells are regularly challenged by harmful pathogens and toxins in the environment, and they must detect these stressors to induce resistance and avoidance responses. A recent study in Cell Research identifies a leucine-rich-repeat receptor-like kinase in Arabidopsis thaliana that functions as a receptor for the toxic aluminum cations prevalent in acidic soils."
Authors: Yunzhi Huang, Zhe Ji, Siyu Zhang and Shan Li.
Journal of Plant Physiology (2024)
Abstract: "Nitrogen (N) is one of the most important nutrients for crop plant performance, however, the excessive application of nitrogenous fertilizers in agriculture significantly increases production costs and causes severe environmental problems. Therefore, comprehensively understanding the molecular mechanisms of N-use efficiency (NUE) with the aim of developing new crop varieties that combine high yields with improved NUE is an urgent goal for achieving more sustainable agriculture. Plant NUE is a complex trait that is affected by multiple factors, of which hormones are known to play pivotal roles. In this review, we focus on the interaction between the biosynthesis and signaling pathways of plant hormones with N metabolism, and summarize recent studies on the interplay between hormones and N, including how N regulates multiple hormone biosynthesis, transport and signaling and how hormones modulate root system architecture (RSA) in response to external N sources. Finally, we explore potential strategies for promoting crop NUE by modulating hormone synthesis, transport and signaling. This provides insights for future breeding of N-efficient crop varieties and the advancement of sustainable agriculture."
Authors: Zhuo Li, Huan Chen, Qingjie Guan, Lixin Li and Yuan Hu Xuan.
Plant Physiology and Biochemistry (2024)
Highlights: • GA signaling positively regulates the resistance of rice to saline-alkali. • GA signaling promotes resistance to saline-alkali stress by increasing the uptake of ammonium in rice. • GA expected to play an important role in the comprehensive utilization of saline-alkali land.
Abstract: "Gibberellic acid (GA) plays important roles in diverse biological processes in plants. However, its function in rice (Oryza sativa) resistance to saline-alkaline (SAK) stress is unclear. This study showed that SAK stimuli changed GA signaling gene expression levels. Genetic analyses using the mutants of key GA signaling regulators, Slender rice 1 (SLR1) and Dwarf 1(D1), demonstrated that SLR1 negatively, while D1 positively regulated the resistance of rice to SAK stress, suggesting that the GA signaling positively regulates the resistance of rice to SAK. Further analyses revealed that SLR1 interacted with and inhibited the transcription activation activity of IDD10 and bZIP23. Furthermore, IDD10 interacted with bZIP23 to activate Ammonium transporter 1;2 (AMT1;2), and slr1, IDD10 OX and bZIP23 OX accumulated more ammonium (NH4+), while idd10 and bzip23 accumulated less NH4+ than the wild-type (WT). In addition, the bzip23 mutant was more sensitive to SAK, while bZIP23 OX was less sensitive compared with the WT, suggesting that bZIP23 positively regulates the resistance of rice to SAK. These findings demonstrate that GA signaling promoted rice's SAK resistance by regulating NH4+ uptake through the SLR1-IDD10-bZIP23 pathway."
Authors: Fengkai Wu, Baba Salifu Yahaya, Ying Gong, Bing He, Junlin Gou, Yafeng He, Jing Li, Yan Kang, Jie Xu, Qingjun Wang, Xuanjun Feng, Qi Tang, Yaxi Liu and Yanli Lu.
PLoS Genetics (2024)
Abstract: "Phosphorus (P) deficiency is one of the most critical factors for plant growth and productivity, including its inhibition of lateral root initiation. Auxin response factors (ARFs) play crucial roles in root development via auxin signaling mediated by genetic pathways. In this study, we found that the transcription factor ZmARF1 was associated with low inorganic phosphate (Pi) stress-related traits in maize. This superior root morphology and greater phosphate stress tolerance could be ascribed to the overexpression of ZmARF1. The knock out mutant zmarf1 had shorter primary roots, fewer root tip number, and lower root volume and surface area. Transcriptomic data indicate that ZmLBD1, a direct downstream target gene, is involved in lateral root development, which enhances phosphate starvation tolerance. A transcriptional activation assay revealed that ZmARF1 specifically binds to the GC-box motif in the promoter of ZmLBD1 and activates its expression. Moreover, ZmARF1 positively regulates the expression of ZmPHR1, ZmPHT1;2, and ZmPHO2, which are key transporters of Pi in maize. We propose that ZmARF1 promotes the transcription of ZmLBD1 to modulate lateral root development and Pi-starvation induced (PSI) genes to regulate phosphate mobilization and homeostasis under phosphorus starvation. In addition, ZmERF2 specifically binds to the ABRE motif of the promoter of ZmARF1 and represses its expression. Collectively, the findings of this study revealed that ZmARF1 is a pivotal factor that modulates root development and confers low-Pi stress tolerance through the transcriptional regulation of the biological function of ZmLBD1 and the expression of key Pi transport proteins."
Authors: Yuwen Zhang, Xingliang Duan, Yuanming Xie and Wei Xuan.
New Crops (2024)
Abstract: "Plant root systems are critical for absorbing water and nutrients and anchoring plants in the soil, and their development is regulated by phytohormones and complex signaling pathways. Recent studies have identified small peptides as essential players in governing root development, binding to specific receptors on the cell membrane, and triggering signaling processes. In this study, we summarize recent advances in small peptide regulation of root system architecture and tissue organization, as well as the molecular interaction between peptides and canonical hormone signaling. Additionally, we discuss the functions of small peptides in modulating root development responses to environmental forces like nitrogen and phosphate starvation, osmotic stress, and soil microbes through the activation of local and systemic signaling pathways. This review offers a comprehensive overview of peptide signaling during plant root development and prospects for further crop breeding applications."
Authors: Momoyo Ito, Yuri Tajima, Mari Ogawa-Ohnishi, Hanna Nishida, Shohei Nosaki, Momona Noda, Naoyuki Sotta, Kensuke Kawade, Takehiro Kamiya, Toru Fujiwara, Yoshikatsu Matsubayashi and Takuya Suzaki.
Nature Communications (2024)
Editors view: The authors show IRON MAN peptides have an essential role in symbiotic nitrogen fixation during legume-rhizobium symbiosis. The peptides additionally function to regulate nitrogen homeostasis by controlling nitrogen-iron balance.
Abstract: "Legumes control root nodule symbiosis (RNS) in response to environmental nitrogen availability. Despite the recent understanding of the molecular basis of external nitrate-mediated control of RNS, it remains mostly elusive how plants regulate physiological processes depending on internal nitrogen status. In addition, iron (Fe) acts as an essential element that enables symbiotic nitrogen fixation; however, the mechanism of Fe accumulation in nodules is poorly understood. Here, we focus on the transcriptome in response to internal nitrogen status during RNS in Lotus japonicus and identify that IRON MAN (IMA) peptide genes are expressed during symbiotic nitrogen fixation. We show that LjIMA1 and LjIMA2 expressed in the shoot and root play systemic and local roles in concentrating internal Fe to the nodule. Furthermore, IMA peptides have conserved roles in regulating nitrogen homeostasis by adjusting nitrogen-Fe balance in L. japonicus and Arabidopsis thaliana. These findings indicate that IMA-mediated Fe provision plays an essential role in regulating nitrogen-related physiological processes."
Authors: Taras P. Pasternak and Douglas Steinmacher.
Plants (2024)
Abstract: "Precise knowledge of all aspects controlling plant tissue culture and in vitro plant regeneration is crucial for plant biotechnologists and their correlated industry, as there is increasing demand for this scientific knowledge, resulting in more productive and resilient plants in the field. However, the development and application of cell and tissue culture techniques are usually based on empirical studies, although some data-driven models are available. Overall, the success of plant tissue culture is dependent on several factors such as available nutrients, endogenous auxin synthesis, organic compounds, and environment conditions. In this review, the most important aspects are described one by one, with some practical recommendations based on basic research in plant physiology and sharing our practical experience from over 20 years of research in this field. The main aim is to help new plant biotechnologists and increase the impact of the plant tissue culture industry worldwide."
Authors: Zhong Jie Ding, Chen Xu, Jing Ying Yan, Yu Xuan Wang, Meng Qi Cui, Jun Jie Yuan, Ya Nan Wang, Gui Xin Li, Jian Xiang Wu, Yun Rong Wu, Ji Ming Xu, Chun Xiao Li, Yuan Zhi Shi, Chuan Zao Mao, Jiang Tao Guo, Jian Min Zhou, Moussa Benhamed, Nicholas P. Harberd and Shao Jian Zheng.
Cell Research (2024)
Abstract: "Plant survival requires an ability to adapt to differing concentrations of nutrient and toxic soil ions, yet ion sensors and associated signaling pathways are mostly unknown. Aluminum (Al) ions are highly phytotoxic, and cause severe crop yield loss and forest decline on acidic soils which represent ∼30% of land areas worldwide. Here we found an Arabidopsis mutant hypersensitive to Al. The gene encoding a leucine-rich-repeat receptor-like kinase, was named Al Resistance1 (ALR1). Al ions binding to ALR1 cytoplasmic domain recruits BAK1 co-receptor kinase and promotes ALR1-dependent phosphorylation of the NADPH oxidase RbohD, thereby enhancing reactive oxygen species (ROS) generation. ROS in turn oxidatively modify the RAE1 F-box protein to inhibit RAE1-dependent proteolysis of the central regulator STOP1, thus activating organic acid anion secretion to detoxify Al. These findings establish ALR1 as an Al ion receptor that confers resistance through an integrated Al-triggered signaling pathway, providing novel insights into ion-sensing mechanisms in living organisms, and enabling future molecular breeding of acid-soil-tolerant crops and trees, with huge potential for enhancing both global food security and forest restoration."
Authors: Hui Wang, Huayang Wang, Houzhou Liu, Tao Wan, Yalin Li, Ketong Zhang, Sergey Shabala, Xuewen Li, Yinglong Chen and Min Yu.
Plant Physiology and Biochemistry (2024)
Highlights • Al stress changed RSA via increasing root GSA of pea. • Exogenous auxin negatively influences the gravitropism of lateral roots by reducing the starch granules in the root tip and changing auxin polar transport. • Al stress changed RSA through the auxin pathway, which is related to the root gravitropic response of plants.
Abstract: "Aluminium (Al) toxicity stands out as a primary cause of crop failure in acidic soils. The root gravity setpoint angle (GSA), one of the important traits of the root system architecture (RSA), plays a pivotal role in enabling plants to adapt to abiotic stress. This study explored the correlation between GSA and Al stress using hydroponic culture with pea (Pisum sativum) plants. The findings revealed that under Al stress, GSA increased in newly developed lateral roots. Notably, this response remained consistent regardless of the treatment duration, extending for at least 3 days during the experiment. Furthermore, exposure to Al led to a reduction in both the size and quantity of starch granules, pivotal components linked to gravity perception. The accumulation of auxin in root transition zone increased. This variation was mirrored in the expression of genes linked to granule formation and auxin efflux, particularly those in the PIN-formed family. This developmental framework suggested a unique role for the root gravitropic response that hinges on starch granules and auxin transport, acting as mediators in the modulation of GSA under Al stress. Exogenous application of indole-3-acetic acid (IAA) and the auxin efflux inhibitor N-1-naphthylphthalamic acid (NPA) had an impact on the root gravitropic response to Al stress. The outcomes indicate that Al stress inhibited polar auxin transport and starch granule formation, the two processes crucial for gravitropism. This impairment led to an elevation in GSA and a reconfiguration of RSA. This study introduces a novel perspective on how plant roots react to Al toxicity, culminating in RSA modification in the context of acidic soil with elevated Al concentrations."
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