Plant Gene Seeker -PGS
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Plant Gene Seeker -PGS
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The histone deacetylase HDA19 controls root cell elongation and modulates a subset of phosphate starvation responses in Arabidopsis

The histone deacetylase HDA19 controls root cell elongation and modulates a subset of phosphate starvation responses in Arabidopsis | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

The length of root epidermal cells and their patterning into files of hair-bearing and non-hair cells are genetically determined but respond with high plasticity to environmental cues. Limited phyto-availability of the essential mineral nutrient phosphate (Pi) increases the number of root hairs by longitudinal shortening of epidermal cells and by reprogramming the fate of cells in positions normally occupied by non-hair cells. Through analysis of the root morphology and transcriptional profiles from transgenic Arabidopsis lines with altered expression of the histone deacetylase HDA19, we show that in an intricate interplay of Pi availability and intrinsic factors, HDA19 controls the epidermal cell length, probably by altering the positional bias that dictates epidermal patterning. In addition, HDA19 regulates several Pi-responsive genes that encode proteins with important regulatory or metabolic roles in the acclimation to Pi deficiency. In particular, HDA19 affects genes encoding SPX (SYG1/Pho81/XPR) domain-containing proteins and genes involved in membrane lipid remodeling, a key response to Pi starvation that increases the free Pi in plants. Our data add a novel, non-transcriptionally regulated component of the Pi signaling network and emphasize the importance of reversible post-translational histone modification for the integration of external signals into intrinsic developmental and metabolic programs.

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Discovering New Biology through Sequencing of RNA

Discovering New Biology through Sequencing of RNA | Plant Gene Seeker -PGS | Scoop.it
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Sequencing of RNA (RNA-Seq) was invented approximately 1 decade ago and has since revolutionized biological research. This update provides a brief historic perspective on the development of RNA-Seq and then focuses on the application of RNA-Seq in qualitative and quantitative analyses of transcriptomes. Particular emphasis is given to aspects of data analysis. Since the wet-lab and data analysis aspects of RNA-Seq are still rapidly evolving and novel applications are continuously reported, a printed review will be rapidly outdated and can only serve to provide some examples and general guidelines for planning and conducting RNA-Seq studies. Hence, selected references to frequently update online resources are given.

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Researchers Identify New Factors That Guide Organization of Plant Roots

Researchers Identify New Factors That Guide Organization of Plant Roots | Plant Gene Seeker -PGS | Scoop.it
Transcriptional control of tissue formation throughout root development
Andres Zurita's insight:

As the root of a growing plant pushes its way through soil, its cells have a lot of organizing to do. New cells must take on the appropriate identities and positions to form distinct layers of tissue that give the root its structure, protect it from the environment, and ensure that it can properly transport materials to and from the rest of the plant.

Howard Hughes Medical Institute scientists have now identified a set of proteins that plays a surprisingly broad role in guiding this tissue formation. The factors, known as the BIRDs, help a root maintain its organization as it grows, guiding several distinct steps in the development of two interior layers of tissue. The study was led by Philip Benfey, an HHMI-Gordon and Betty Moore Foundation investigator at Duke University. Benfey and his colleagues published their findings on October 23, 2015, in the journal Science.

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Strigolactones spatially influence lateral root development through the cytokinin signaling network

Strigolactones spatially influence lateral root development through the cytokinin signaling network | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

Strigolactones are important rhizosphere signals that act as phytohormones and have multiple functions, including modulation of lateral root (LR) development. Here, we show that treatment with the strigolactone analog GR24 did not affect LR initiation, but negatively influenced LR priming and emergence, the latter especially near the root–shoot junction. The cytokinin module ARABIDOPSIS HISTIDINE KINASE3(AHK3)/ARABIDOPSIS RESPONSE REGULATOR1 (ARR1)/ARR12 was found to interact with the GR24-dependent reduction in LR development, because mutants in this pathway rendered LR development insensitive to GR24. Additionally, pharmacological analyses, mutant analyses, and gene expression analyses indicated that the affected polar auxin transport stream in mutants of the AHK3/ARR1/ARR12 module could be the underlying cause. Altogether, the data reveal that the GR24 effect on LR development depends on the hormonal landscape that results from the intimate connection with auxins and cytokinins, two main players in LR development.

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Proline affects the size of the root meristematic zone in Arabidopsis

Proline affects the size of the root meristematic zone in Arabidopsis | Plant Gene Seeker -PGS | Scoop.it
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Background

We reported previously that root elongation in Arabidopsis is promoted by exogenous proline, raising the possibility that this amino acid may modulate root growth.

Results

To evaluate this hypothesis we used a combination of genetic, pharmacological and molecular analyses, and showed that proline specifically affects root growth by modulating the size of the root meristem. The effects of proline on meristem size are parallel to, and independent from, hormonal pathways, and do not involve the expression of genes controlling cell differentiation at the transition zone. On the contrary, proline appears to control cell division in early stages of postembryonic root development, as shown by the expression of the G2/M-specific CYCLINB1;1 (CYCB1;1) gene.

Conclusions

The overall data suggest that proline can modulate the size of root meristematic zone in Arabidopsis likely controlling cell division and, in turn, the ratio between cell division and cell differentiation.

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Drought susceptibility of modern rice varieties: an effect of linkage of drought tolerance with undesirable traits : Scientific Reports

Drought susceptibility of modern rice varieties: an effect of linkage of drought tolerance with undesirable traits : Scientific Reports | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

Green Revolution (GR) rice varieties are high yielding but typically drought sensitive. This is partly due to the tight linkage between the loci governing plant height and drought tolerance. This linkage is illustrated here through characterization of qDTY1.1, a QTL for grain yield under drought that co-segregates with the GR gene sd1 for semi-dwarf plant height. We report that the loss of the qDTY1.1 allele during the GR was due to its tight linkage in repulsion with the sd1 allele. Other drought-yield QTLs (qDTY) also showed tight linkage with traits rejected in GR varieties. Genetic diversity analysis for 11 different qDTYregions grouped GR varieties separately from traditional drought-tolerant varieties, and showed lower frequency of drought tolerance alleles. The increased understanding and breaking of the linkage between drought tolerance and undesirable traits has led to the development of high-yielding drought-tolerant dwarf lines with positive qDTY alleles and provides new hope for extending the benefits of the GR to drought-prone rice-growing regions.

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Developmental, transcriptome, and genetic alterations associated with parthenocarpy in the grapevine seedless somatic variant Corinto bianco

Developmental, transcriptome, and genetic alterations associated with parthenocarpy in the grapevine seedless somatic variant Corinto bianco | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

Seedlessness is a relevant trait in grapevine cultivars intended for fresh consumption or raisin production. Previous DNA marker analysis indicated that Corinto bianco (CB) is a parthenocarpic somatic variant of the seeded cultivar Pedro Ximenes (PX). This study compared both variant lines to determine the basis of this parthenocarpic phenotype. At maturity, CB seedless berries were 6-fold smaller than PX berries. The macrogametophyte was absent from CB ovules, and CB was also pollen sterile. Occasionally, one seed developed in 1.6% of CB berries. Microsatellite genotyping and flow cytometry analyses of seedlings generated from these seeds showed that most CB viable seeds were formed by fertilization of unreduced gametes generated by meiotic diplospory, a process that has not been described previously in grapevine. Microarray and RNA-sequencing analyses identified 1958 genes that were differentially expressed between CB and PX developing flowers. Genes downregulated in CB were enriched in gametophyte-preferentially expressed transcripts, indicating the absence of regular post-meiotic germline development in CB. RNA-sequencing was also used for genetic variant calling and 14 single-nucleotide polymorphisms distinguishing the CB and PX variant lines were detected. Among these, CB-specific polymorphisms were considered as candidate parthenocarpy-responsible mutations, including a putative deleterious substitution in a HAL2-like protein. Collectively, these results revealed that the absence of a mature macrogametophyte, probably due to meiosis arrest, coupled with a process of fertilization-independent fruit growth, caused parthenocarpy in CB. This study provides a number of grapevine parthenocarpy-responsible candidate genes and shows how genomic approaches can shed light on the genetic origin of woody crop somatic variants.

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miR408 is involved in abiotic stress responses in Arabidopsis -

miR408 is involved in abiotic stress responses in Arabidopsis - | Plant Gene Seeker -PGS | Scoop.it

Ma - 2015 - The Plant Journal 

Andres Zurita's insight:

MicroRNAs (miRNAs) are small RNAs that regulate the expression of target genes post-transcriptionally; they are known to play major roles in development and responses to abiotic stress. miR408 is a highly conserved miRNA in plants that responds to the availability of copper and targets genes encoding copper-containing proteins. It was recently recognized to be an important component of the HY5–SPL7 gene network that mediates a coordinated response to light and copper, illustrating its central role in the response of plants to the environment. Expression of miR408 is significantly affected by a variety of developmental and ‏environmental conditions; however, its biological function is ‏unknown. Involvement of miR408 in the abiotic stress response was investigated in Arabidopsis. Expression of miR408, as well as its target genes, was investigated in response to salinity, cold, oxidative stress, drought and osmotic stress. Analyses of transgenic plants with modulated miR408expression revealed that higher miR408 expression leads to improved tolerance to salinity, cold and oxidative stress, but enhanced sensitivity to drought and osmotic stress. Cellular antioxidant capacity was enhanced in plants with elevated miR408 expression, as manifested by reduced levels of reactive oxygen species and induced expression of genes associated with antioxidative functions, including Cu/Zn superoxide dismutases (CSD1 and CSD2) and glutathione-S-transferase (GST-U25), as well as auxiliary genes: the copper chaperone CCS1and the redox stress-associated gene SAP12. Overall, the results demonstrate significant involvement of miR408 in abiotic stress responses, emphasizing the central function of miR408 in plant survival.

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Frontiers | Ethylene and plant responses to phosphate deficiency | Plant Nutrition

Andres Zurita's insight:

Phosphorus is an essential macronutrient for plant growth and development. Phosphate (Pi), the major form of phosphorus that plants take up through roots, however, is limited in most soils. To cope with Pi deficiency, plants activate an array of adaptive responses to reprioritize internal Pi use and enhance external Pi acquisition. These responses are modulated by sophisticated regulatory networks through both local and systemic signaling, but the signaling mechanisms are poorly understood. Early studies suggested that the phytohormone ethylene plays a key role in Pi deficiency-induced remodeling of root system architecture. Recently, ethylene was also shown to be involved in the regulation of other signature responses of plants to Pi deficiency. In this article, we review how researchers have used pharmacological and genetic approaches to dissect the roles of ethylene in regulating Pi deficiency-induced developmental and physiological changes. The interactions between ethylene and other signaling molecules, such as sucrose, auxin, and microRNA399, in the control of plant Pi responses are also examined. Finally, we provide a perspective for the future research in this field.

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Grapevine and Arabidopsis cation-chloride cotransporters localise to the Golgi and trans-Golgi network and indirectly influence long-distance ion homeostasis and plant salt tolerance

Grapevine and Arabidopsis cation-chloride cotransporters localise to the Golgi and trans-Golgi network and indirectly influence long-distance ion homeostasis and plant salt tolerance | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

Plant cation-chloride cotransporters (CCCs) have been implicated in conferring salt tolerance. They are predicted to improve shoot salt exclusion by directly catalysing the retrieval of sodium (Na+) and chloride ions (Cl-) from the root xylem. We investigated whether VvCCC from grapevine (Vitis vinifera L.) has a role in salt tolerance by cloning and functionally characterising the gene from Cabernet Sauvignon. Amino acid sequence analysis revealed that VvCCC shares a high degree of similarity with other plant CCCs. A VvCCC-YFP translational fusion protein localised to the Golgi and trans-Golgi network (TGN), not the plasma membrane, when expressed transiently in tobacco (Nicotiana benthamiana) leaves and Arabidopsis thaliana mesophyll protoplasts. AtCCC-GFP from Arabidopsis also localised to Golgi and TGN. In Xenopus laevis oocytes, VvCCC targeted to the plasma membrane where it catalysed bumetanide sensitive 36Cl-, 22Na+ and 86Rb+ uptake, suggesting that VvCCC (like AtCCC) belongs to the NKCC class of CCCs. Expression of VvCCC in an Arabidopsis ccc knockout mutant abolished the mutant's stunted growth phenotypes, and reduced shoot Cl- and Na+ content to wild-type levels after growing plants in 50 mM NaCl. In Vitis vinifera roots, VvCCC transcript abundance was not regulated by Cl- treatment and was present at similar levels in both the root stele and cortex of three Vitis genotypes that exhibit differential shoot salt exclusion. Our findings indicate that CCC function is conserved between grapevine and Arabidopsis, but neither protein is likely to directly mediate ion transfer with the xylem or have a direct role in salt tolerance.

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Spatio-temporal relief from hypoxia and production of reactive oxygen species during bud burst in grapevine (Vitis vinifera)

Spatio-temporal relief from hypoxia and production of reactive oxygen species during bud burst in grapevine (Vitis vinifera) | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

Background and Aims

Plants regulate cellular oxygen partial pressures (pO2), together with reduction/oxidation (redox) state in order to manage rapid developmental transitions such as bud burst after a period of quiescence. However, our understanding of pO2 regulation in complex meristematic organs such as buds is incomplete and, in particular, lacks spatial resolution.

Methods

The gradients in pO2 from the outer scales to the primary meristem complex were measured in grapevine (Vitis vinifera) buds, together with respiratory CO2 production rates and the accumulation of superoxide and hydrogen peroxide, from ecodormancy through the first 72 h preceding bud burst, triggered by the transition from low to ambient temperatures.

Key Results

Steep internal pO2 gradients were measured in dormant buds with values as low as 2·5 kPa found in the core of the bud prior to bud burst. Respiratory CO2 production rates increased soon after the transition from low to ambient temperatures and the bud tissues gradually became oxygenated in a patterned process. Within 3 h of the transition to ambient temperatures, superoxide accumulation was observed in the cambial meristem, co-localizing with lignified cellulose associated with pro-vascular tissues. Thereafter, superoxide accumulated in other areas subtending the apical meristem complex, in the absence of significant hydrogen peroxide accumulation, except in the cambial meristem. By 72 h, the internal pO2 gradient showed a biphasic profile, where the minimum pO2 was external to the core of the bud complex.

Conclusions

Spatial and temporal control of the tissue oxygen environment occurs within quiescent buds, and the transition from quiescence to bud burst is accompanied by a regulated relaxation of the hypoxic state and accumulation of reactive oxygen species within the developing cambium and vascular tissues of the heterotrophic grapevine buds.

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Role of phenotypic plasticity and population differentiation in adaptation to novel environmental conditions

Role of phenotypic plasticity and population differentiation in adaptation to novel environmental conditions | Plant Gene Seeker -PGS | Scoop.it

Volis - 2015 - Ecology and Evolution - Wiley Online Library

Andres Zurita's insight:

Species can adapt to new environmental conditions either through individual phenotypic plasticity, intraspecific genetic differentiation in adaptive traits, or both. Wild emmer wheat, Triticum dicoccoides, an annual grass with major distribution in Eastern Mediterranean region, is predicted to experience in the near future, as a result of global climate change, conditions more arid than in any part of the current species distribution. To understand the role of the above two means of adaptation, and the effect of population range position, we analyzed reaction norms, extent of plasticity, and phenotypic selection across two experimental environments of high and low water availability in two core and two peripheral populations of this species. We studied 12 quantitative traits, but focused primarily on the onset of reproduction and maternal investment, which are traits that are closely related to fitness and presumably involved in local adaptation in the studied species. We hypothesized that the population showing superior performance under novel environmental conditions will either be genetically differentiated in quantitative traits or exhibit higher phenotypic plasticity than the less successful populations. We found the core population K to be the most plastic in all three trait categories (phenology, reproductive traits, and fitness) and most successful among populations studied, in both experimental environments; at the same time, the core K population was clearly genetically differentiated from the two edge populations. Our results suggest that (1) two means of successful adaptation to new environmental conditions, phenotypic plasticity and adaptive genetic differentiation, are not mutually exclusive ways of achieving high adaptive ability; and (2) colonists from some core populations can be more successful in establishing beyond the current species range than colonists from the range extreme periphery with conditions seemingly closest to those in the new environment.

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Resolving Conflicts between Agriculture and the Natural Environment

Resolving Conflicts between Agriculture and the Natural Environment | Plant Gene Seeker -PGS | Scoop.it
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Abstract

Agriculture dominates the planet. Yet it has many environmental costs that are unsustainable, especially as global food demand rises. Here, we evaluate ways in which different parts of the world are succeeding in their attempts to resolve conflict between agriculture and wild nature. We envision that coordinated global action in conserving land most sensitive to agricultural activities and policies that internalise the environmental costs of agriculture are needed to deliver a more sustainable future.

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Grapevine and Arabidopsis Cation-Chloride Cotransporters Localize to the Golgi and Trans-Golgi Network and Indirectly Influence Long-Distance Ion Transport and Plant Salt Tolerance

Grapevine and Arabidopsis Cation-Chloride Cotransporters Localize to the Golgi and Trans-Golgi Network and Indirectly Influence Long-Distance Ion Transport and Plant Salt Tolerance | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

Plant cation-chloride cotransporters (CCCs) have been implicated in conferring salt tolerance. They are predicted to improve shoot salt exclusion by directly catalyzing the retrieval of sodium (Na+) and chloride (Cl−) ions from the root xylem. We investigated whether grapevine (Vitis vinifera [Vvi]) CCC has a role in salt tolerance by cloning and functionally characterizing the gene from the cultivar Cabernet Sauvignon. Amino acid sequence analysis revealed that VviCCC shares a high degree of similarity with other plant CCCs. A VviCCC-yellow fluorescent protein translational fusion protein localized to the Golgi and the trans-Golgi network and not the plasma membrane when expressed transiently in tobacco (Nicotiana benthamiana) leaves and Arabidopsis (Arabidopsis thaliana) mesophyll protoplasts. AtCCC-green fluorescent protein from Arabidopsis also localized to the Golgi and the trans-Golgi network. In Xenopus laevis oocytes, VviCCC targeted to the plasma membrane, where it catalyzed bumetanide-sensitive 36Cl–, 22Na+, and 86Rb+ uptake, suggesting that VviCCC (like AtCCC) belongs to the Na+-K+-2Cl– cotransporter class of CCCs. Expression of VviCCCin an Arabidopsis ccc knockout mutant abolished the mutant’s stunted growth phenotypes and reduced shoot Cl– and Na+ content to wild-type levels after growing plants in 50 mM NaCl. In grapevine roots, VviCCC transcript abundance was not regulated by Cl– treatment and was present at similar levels in both the root stele and cortex of three Vitis spp. genotypes that exhibit differential shoot salt exclusion. Our findings indicate that CCC function is conserved between grapevine and Arabidopsis, but neither protein is likely to directly mediate ion transfer with the xylem or have a direct role in salt tolerance.

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Proteins of Unknown Biochemical Function: A Persistent Problem and a Roadmap to Help Overcome It

Proteins of Unknown Biochemical Function: A Persistent Problem and a Roadmap to Help Overcome It | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

The number of sequenced genomes is rapidly increasing, but functional annotation of the genes in these genomes lags far behind. Even in Arabidopsis (Arabidopsis thaliana), only approximately 40% of enzyme- and transporter-encoding genes have credible functional annotations, and this number is even lower in nonmodel plants. Functional characterization of unknown genes is a challenge, but various databases (e.g. for protein localization and coexpression) can be mined to provide clues. If homologous microbial genes exist—and about one-half the genes encoding unknown enzymes and transporters in Arabidopsis have microbial homologs—cross-kingdom comparative genomics can powerfully complement plant-based data. Multiple lines of evidence can strengthen predictions and warrant experimental characterization. In some cases, relatively quick tests in genetically tractable microbes can determine whether a prediction merits biochemical validation, which is costly and demands specialized skills.

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Understanding crop genetic diversity under modern plant breeding - Springer

Understanding crop genetic diversity under modern plant breeding - Springer | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

Modern plant breeding has made a profound impact on food production and will continue to play a vital role in world food security. For sustainable agriculture, a compromise should be sought between maximizing crop yield under changing climate and minimizing crop failure under unfavorable conditions. Such a compromise requires better understanding of the impacts of plant breeding on crop genetic diversity. Efforts have been made over the last three decades to assess crop genetic diversity using molecular marker technologies. However, these assessments have revealed some temporal diversity patterns that are largely inconsistent with our perception that modern plant breeding reduces crop genetic diversity. An attempt was made in this review to explain such discrepancies by examining empirical assessments of crop genetic diversity and theoretical investigations of genetic diversity changes over time under artificial selection. It was found that many crop genetic diversity assessments were not designed to assess diversity impacts from specific plant breeding programs, while others were experimentally inadequate and contained technical biases from the sampling of cultivars and genomes. Little attention has been paid to theoretical investigations on crop genetic diversity changes from plant breeding. A computer simulation of five simplified breeding schemes showed the substantial effects of plant breeding on the retention of heterozygosity over generations. It is clear that more efforts are needed to investigate crop genetic diversity in space and time under plant breeding to achieve sustainable crop production.

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Polymorphisms and minihaplotypes in the VvNAC26 gene associate with berry size variation in grapevine

Polymorphisms and minihaplotypes in the VvNAC26 gene associate with berry size variation in grapevine | Plant Gene Seeker -PGS | Scoop.it

Median-joining phylogenetic network constructed for the 26 VvNAC26 haplotypes detected (H1 – H26). Each haplotype is represented by a circle, which size (see code) is proportional to its frequency in the set of varieties analyzed. Their inner color/s indicate the proportion of varieties assigned to each of the genetic groups detected by STRUCTURE (see color code, Adm.: admixed). Lines connecting haplotypes represent phylogenetic branches, and small transversal lines represent mutational steps (only those polymorphisms significantly associated with berry and/or bunch traits appear named, according to Table 4). Black dots represent missing intermediate haplotypes. HGA and HGB indicate the two different haplogroups detected (see Additional file 10). MH1, MH2, MH3, MH4 and MH5 indicate the different minihapolotypes inferred on the basis of polymorphisms Y117, W-962 and IND-694 (see Table 5)

Andres Zurita's insight:

Background
Domestication and selection of Vitis vinifera L. for table and wine grapes has led to a large level of berry size diversity in current grapevine cultivars. Identifying the genetic basis for this natural variation is paramount both for breeding programs and for elucidating which genes contributed to crop evolution during domestication and selection processes. The gene VvNAC26, which encodes a NAC domain-containing transcription factor, has been related to the early development of grapevine flowers and berries. It was selected as candidate gene for an association study to elucidate its possible participation in the natural variation of reproductive traits in cultivated grapevine.

Methods
A grapevine collection of 114 varieties was characterized during three consecutive seasons for different berry and bunch traits. The promoter and coding regions of VvNAC26 gene (VIT_01s0026g02710) were sequenced in all the varieties of the collection, and the existing polymorphisms (SNP and INDEL) were detected. The corresponding haplotypes were inferred and used for a phylogenetic analysis. The possible associations between genotypic and phenotypic data were analyzed independently for each season data, using different models and significance thresholds.

Results
A total of 30 non-rare polymorphisms were detected in the VvNAC26 sequence, and 26 different haplotypes were inferred. Phylogenetic analysis revealed their clustering in two major haplogroups with marked phenotypic differences in berry size between varieties harboring haplogroup-specific alleles. After correcting the statistical models for the effect of the population genetic stratification, we found a set of polymorphisms associated with berry size explaining between 8.4 and 21.7 % (R2) of trait variance, including those generating the differentiation between both haplogroups. Haplotypes built from only three polymorphisms (minihaplotypes) were also associated with this trait (R2: 17.5 – 26.6 %), supporting the involvement of this gene in the natural variation for berry size.

Conclusions
Our results suggest the participation of VvNAC26 in the determination of the grape berry final size. Different VvNAC26 polymorphisms and their combination showed to be associated with different features of the fruit. The phylogenetic relationships between the VvNAC26 haplotypes and the association results indicate that this nucleotide variation may have contributed to the differentiation between table and wine grapes.

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Physiological and transcriptional regulation in poplar roots and leaves during acclimation to high temperature and drought

Physiological and transcriptional regulation in poplar roots and leaves during acclimation to high temperature and drought | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

To elucidate the physiological and transcriptional regulatory mechanisms that underlie the responses of poplars to high temperature (HT) and/or drought in woody plants, we exposed Populus alba × P. tremula var. glandulosa saplings to ambient temperature (AT) or HT under 80% or 40% field capacities, or no watering. HT increased the foliar total carbon (C) concentrations, and foliar δ13C and δ18O. HT triggered heat stress signaling via increasing levels of ABA and IAA in poplar roots and leaves. After perception of HT, poplars initiated osmotic adjustment by increasing foliar sucrose and root galactose levels. In agreement with the HT-induced heat stress and the changes in the levels of ABA and carbohydrates, we detected increased transcript levels of HSP18 and HSP21, as well as NCED3 in the roots and leaves, and the sugar transporter gene STP14 in the roots. Compared with AT, drought induced greater enhancement of foliar δ13C and δ18O in poplars at HT. Similarly, drought caused greater stimulation of the ABA and foliar glucose levels in poplars at HT than at AT. Correspondingly, desiccation led to greater increases in the mRNA levels of HSP18, HSP21, NCED3, STP14 and INT1 in poplar roots at HT than at AT. These results suggest that HT has detrimental effects on physiological processes and it induces the transcriptional regulation of key genes involved in heat stress responses, ABA biosynthesis and sugar transport, and HT can cause greater changes in drought-induced physiological and transcriptional responses in poplar roots and leaves.

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Salinity tolerance of crops – what is the cost?

Salinity tolerance of crops – what is the cost? | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

Soil salinity reduces crop yield. The extent and severity of salt-affected agricultural land is predicted to worsen as a result of inadequate drainage of irrigated land, rising water tables and global warming. The growth and yield of most plant species are adversely affected by soil salinity, but varied adaptations can allow some crop cultivars to continue to grow and produce a harvestable yield under moderate soil salinity. Significant costs are associated with saline soils: the economic costs to the farming community and the energy costs of plant adaptations. We briefly consider mechanisms of adaptation and highlight recent research examples through a lens of their applicability to improving the energy efficiency of crops under saline field conditions.

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AUX1 and PIN2 Protect Lateral Root Formation in Arabidopsis under Fe Stress

AUX1 and PIN2 Protect Lateral Root Formation in Arabidopsis under Fe Stress | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

A stunted root system is a significant symptom of Fe toxicity, yet little is known about the effects of excess Fe on lateral root (LR) development. In this work, we show that excess Fe has different effects on LR development in different portions of the Arabidopsis root system, and that inhibitory effects on the LR initiation are only seen in roots newly formed during excess Fe exposure. We show that root tip contact with Fe is both necessary and sufficient for LR inhibition and that the auxin, but not abscisic acid, pathway is engaged centrally in the initial stages of excess Fe exposure. Furthermore, Fe stress significantly reduced PIN-FORMED2 (PIN2)-green fluorescent protein (GFP) expression in root tips, and pin2-1 mutants exhibited significantly fewer LR initiation events under excess Fe than wild-type (WT). Exogenous application of both Fe and GSH together increased PIN2-GFP expression and the number of LR initiation events compared to Fe treatment alone. The ethylene inhibitor aminoethoxyvinylglycine (AVG) intensified Fe-dependent inhibition of LR formation in the WT, and this inhibition was significantly reduced in the ethylene-overproduction mutant eto1-1. We show that AUX1 is a critical component in the mediation of endogenous ethylene effects on LR formation under excess Fe stress. Our findings demonstrate the relationship between excess-Fe-dependent PIN2 expression and LR formation and the potential role of AUX1 in ethylene-mediated LR tolerance, and suggest that AUX1 and PIN2 protect LR formation in Arabidopsis thaliana during the early stages of Fe stress.

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Transcription factor WRKY46 modulates the development of Arabidopsis lateral roots in osmotic/salt stress conditions via regulation of ABA signaling and auxin homeostasis

Transcription factor WRKY46 modulates the development of Arabidopsis lateral roots in osmotic/salt stress conditions via regulation of ABA signaling and auxin homeostasis | Plant Gene Seeker -PGS | Scoop.it
Andres Zurita's insight:

The development of lateral roots (LR) is known to be severely inhibited by salt or osmotic stress. However, the molecular mechanisms underlying LR development in osmotic/salt stress conditions are poorly understood. Here we show that the gene encoding the WRKY transcription factor WRKY46 (WRKY46) is expressed throughout lateral root primordia (LRP) during early LR development and that expression is subsequently restricted to the stele of the mature LR. In osmotic/salt stress conditions, lack of WRKY46 (in loss-of-function wrky46 mutants) significantly reduces, while overexpression of WRKY46 enhances, LR development. We also show that exogenous auxin largely restores LR development in wrky46 mutants, and that the auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) inhibits LR development in both wild-type (WT; Col-0) and in a line overexpressing WRKY46 (OV46). Subsequent analysis of abscisic acid (ABA)-related mutants indicated that WRKY46 expression is down-regulated by ABA signaling, and up-regulated by an ABA-independent signal induced by osmotic/salt stress. Next, we show that expression of the DR5:GUS auxin response reporter is reduced in roots of wrky46 mutants, and that both wrky46 mutants and OV46 display altered root levels of free indole-3-acetic acid (IAA) and IAA conjugates. Subsequent RT-qPCR and ChIP-qPCR experiments indicated that WRKY46 directly regulates the expression of ABI4 and of genes regulating auxin conjugation. Finally, analysis of wrky46 abi4 double mutant plants confirms that ABI4 acts downstream of WRKY46. In summary, our results demonstrate that WRKY46 contributes to the feedforward inhibition of osmotic/salt stress-dependent LR inhibition via regulation of ABA signaling and auxin homeostasis.

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Differential Role for Trehalose Metabolism in Salt-Stressed Maize

Differential Role for Trehalose Metabolism in Salt-Stressed Maize | Plant Gene Seeker -PGS | Scoop.it
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Little is known about how salt impacts primary metabolic pathways of C4 plants, particularly related to kernel development and seed set. Osmotic stress was applied to maize (Zea mays) B73 by irrigation with increasing concentrations of NaCl from the initiation of floral organs until 3 d after pollination. At silking, photosynthesis was reduced to only 2% of control plants. Salt treatment was found to reduce spikelet growth, silk growth, and kernel set. Osmotic stress resulted in higher concentrations of sucrose (Suc) and hexose sugars in leaf, cob, and kernels at silking, pollination, and 3 d after pollination. Citric acid cycle intermediates were lower in salt-treated tissues, indicating that these sugars were unavailable for use in respiration. The sugar-signaling metabolite trehalose-6-phosphate was elevated in leaf, cob, and kernels at silking as a consequence of salt treatment but decreased thereafter even as Suc levels continued to rise. Interestingly, the transcripts of trehalose pathway genes were most affected by salt treatment in leaf tissue. On the other hand, transcripts of the SUCROSE NONFERMENTING-RELATED KINASE1 (SnRK1) marker genes were most affected in reproductive tissue. Overall, both source and sink strength are reduced by salt, and the data indicate that trehalose-6-phosphate and SnRK1 may have different roles in source and sink tissues. Kernel abortion resulting from osmotic stress is not from a lack of carbohydrate reserves but from the inability to utilize these energy reserves.

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Regulation of Chloroplast Protein Import by the Ubiquitin E3 Ligase SP1 Is Important for Stress Tolerance in Plants

Regulation of Chloroplast Protein Import by the Ubiquitin E3 Ligase SP1 Is Important for Stress Tolerance in Plants | Plant Gene Seeker -PGS | Scoop.it
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Highlights

 

Levels of the chloroplast E3 ligase SP1 influence plant abiotic stress toleranceEffects of SP1 on stress tolerance are linked to reactive oxygen species levelsSP1 acts to deplete the chloroplast protein import (TOC) machinery under stressTOC depletion by SP1 is linked to reduced plastid import of photosynthesis proteins

 

Summary

Chloroplasts are the organelles responsible for photosynthesis in plants [ 1, 2 ]. The chloroplast proteome comprises ∼3,000 different proteins, including components of the photosynthetic apparatus, which are highly abundant. Most chloroplast proteins are nucleus-encoded and imported following synthesis in the cytosol. Such import is mediated by multiprotein complexes in the envelope membranes that surround each organelle [ 3, 4 ]. The translocon at the outer envelope membrane of chloroplasts (TOC) mediates client protein recognition and early stages of import. The TOC apparatus is regulated by the ubiquitin-proteasome system (UPS) in a process controlled by the envelope-localized ubiquitin E3 ligase SUPPRESSOR OF PPI1 LOCUS1 (SP1) [ 5, 6 ]. Previous work showed that SP1-mediated regulation of chloroplast protein import contributes to the organellar proteome changes that occur during plant development (e.g., during de-etiolation). Here, we reveal a critical role for SP1 in plant responses to abiotic stress, which is a major and increasing cause of agricultural yield losses globally [ 7 ]. Arabidopsis plants lacking SP1 are hypersensitive to salt, osmotic, and oxidative stresses, whereas plants overexpressing SP1 are considerably more stress tolerant than wild-type. We present evidence that SP1 acts to deplete the TOC apparatus under stress conditions to limit the import of photosynthetic apparatus components, which may attenuate photosynthetic activity and reduce the potential for reactive oxygen species production and photo-oxidative damage. Our results indicate that chloroplast protein import is responsive to environmental cues, enabling dynamic regulation of the organellar proteome, and suggest new approaches for improving stress tolerance in crops.

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Interplay between vitamin E and phosphorus availability in the control of longevity in Arabidopsis thaliana

Interplay between vitamin E and phosphorus availability in the control of longevity in Arabidopsis thaliana | Plant Gene Seeker -PGS | Scoop.it
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Background and Aims 

Vitamin E helps to control the cellular redox state by reacting with singlet oxygen and preventing the propagation of lipid peroxidation in thylakoid membranes. Both plant ageing and phosphorus deficiency can trigger accumulation of reactive oxygen species, leading to damage to the photosynthetic apparatus. This study investigates how phosphorus availability and vitamin E interact in the control of plant longevity in the short-lived annual Arabidopsis thaliana.


Methods 

The responses of tocopherol cyclase (VTE1)- and γ-tocopherol methyltransferase (VTE4)-null mutants to various levels of phosphorus availability was compared with that of wild-type plants. Longevity (time from germination to rosette death) and the time taken to pass through different developmental stages were determined, and measurements were taken of photosynthetic efficiency, pigment concentration, lipid peroxidation, vitamin E content and jasmonate content.


Key Results 

The vte1 mutant showed accelerated senescence under control conditions, excess phosphorus and mild phosphorus deficiency, suggesting a delaying, protective effect of α-tocopherol during plant senescence. However, under severe phosphorus deficiency the lack of α-tocopherol paradoxically increased longevity in the vte1 mutant, while senescence was accelerated in wild-type plants. Reduced photoprotection in vitamin E-deficient mutants led to increased levels of defence chemicals (as indicated by jasmonate levels) under severe phosphorus starvation in the vte4 mutant and under excess phosphorus and mild phosphorus starvation in the vte1 mutant, indicating a trade-off between the capacity for photoprotection and the activation of chemical defences (jasmonate accumulation).


Conclusions

Vitamin E increases plant longevity under control conditions and mild phosphorus starvation, but accelerates senescence under severe phosphorus limitation. Complex interactions are revealed between phosphorus availability, vitamin E and the potential to synthesize jasmonates, suggesting a trade-off between photoprotection and the activation of chemical defences in the plants.

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Grapevine and Arabidopsis cation-chloride cotransporters localise to the Golgi and trans-Golgi network and indirectly influence long-distance ion homeostasis and plant salt tolerance

Grapevine and Arabidopsis cation-chloride cotransporters localise to the Golgi and trans-Golgi network and indirectly influence long-distance ion homeostasis and plant salt tolerance | Plant Gene Seeker -PGS | Scoop.it
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Plant cation-chloride cotransporters (CCCs) have been implicated in conferring salt tolerance. They are predicted to improve shoot salt exclusion by directly catalysing the retrieval of sodium (Na+) and chloride ions (Cl-) from the root xylem. We investigated whether VvCCC from grapevine (Vitis vinifera L.) has a role in salt tolerance by cloning and functionally characterising the gene from Cabernet Sauvignon. Amino acid sequence analysis revealed that VvCCC shares a high degree of similarity with other plant CCCs. A VvCCC-YFP translational fusion protein localised to the Golgi and trans-Golgi network (TGN), not the plasma membrane, when expressed transiently in tobacco (Nicotiana benthamiana) leaves and Arabidopsis thaliana mesophyll protoplasts. AtCCC-GFP from Arabidopsis also localised to Golgi and TGN. In Xenopus laevis oocytes, VvCCC targeted to the plasma membrane where it catalysed bumetanide sensitive 36Cl-, 22Na+ and 86Rb+ uptake, suggesting that VvCCC (like AtCCC) belongs to the NKCC class of CCCs. Expression of VvCCC in an Arabidopsis ccc knockout mutant abolished the mutant's stunted growth phenotypes, and reduced shoot Cl- and Na+ content to wild-type levels after growing plants in 50 mM NaCl. In Vitis vinifera roots, VvCCC transcript abundance was not regulated by Cl- treatment and was present at similar levels in both the root stele and cortex of three Vitis genotypes that exhibit differential shoot salt exclusion. Our findings indicate that CCC function is conserved between grapevine and Arabidopsis, but neither protein is likely to directly mediate ion transfer with the xylem or have a direct role in salt tolerance.

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