RESUMEN

Genomic DNA methylation patterns play a crucial role in the developmental processes of plants and mammals. In this study, we aimed to investigate the significant effects of epigenetic mechanisms on the development of soybean seedlings and metabolic pathways. Our analyses show that 5-azaC-treatment affects radicle development from two Days After Imbibition (DAI), as well as both shoot and root development. We examined the expression levels of key genes related to DNA methylation and demethylation pathways, such as DRM2, which encodes RNA-directed DNA Methylation (RdDM) pathway, SAM synthase, responsible for methyl group donation, and ROS1, a DNA demethylase. In treated seedling roots, we observed an increase in DRM2 expression and a decrease in ROS1 expression. Additionally, 5-azaC treatment altered protein accumulation, indicating epigenetic control over stress response while inhibiting nitrogen assimilation, urea cycle, and glycolysis-related proteins. Furthermore, it influenced the levels of various phytohormones and metabolites crucial for seedling growth, such as ABA, IAA, ethylene, polyamines (PUT and Cad), and free amino acids, suggesting that epigenetic changes may shape soybean responses to pathogens, abiotic stress, and nutrient absorption. Our results assist in understanding how hypomethylation shapes soybean responses to pathogens, abiotic stress, and nutrient absorption crucial for seedling growth, suggesting that the plant's assimilation of carbon and nitrogen, along with hormone pathways, may be influenced by epigenetic changes.

Asunto(s)

Metilación de ADN , Glycine max , Redes y Vías Metabólicas , Reguladores del Crecimiento de las Plantas , Metilación de ADN/genética , Glycine max/genética , Glycine max/metabolismo , Glycine max/crecimiento & desarrollo , Reguladores del Crecimiento de las Plantas/metabolismo , Redes y Vías Metabólicas/genética , Redes y Vías Metabólicas/efectos de los fármacos , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Plantones/genética , Plantones/crecimiento & desarrollo , Plantones/metabolismo , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Epigénesis Genética , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genética

RESUMEN

Nitrate is a nutrient and signal that regulates gene expression. The nitrate response has been extensively characterized at the organism, organ, and cell-type-specific levels, but intracellular mRNA dynamics remain unexplored. To characterize nuclear and cytoplasmic transcriptome dynamics in response to nitrate, we performed a time-course expression analysis after nitrate treatment in isolated nuclei, cytoplasm, and whole roots. We identified 402 differentially localized transcripts (DLTs) in response to nitrate treatment. Induced DLT genes showed rapid and transient recruitment of the RNA polymerase II, together with an increase in the mRNA turnover rates. DLTs code for genes involved in metabolic processes, localization, and response to stimulus indicating DLTs include genes with relevant functions for the nitrate response that have not been previously identified. Using single-molecule RNA FISH, we observed early nuclear accumulation of the NITRATE REDUCTASE 1 (NIA1) transcripts in their transcription sites. We found that transcription of NIA1, a gene showing delayed cytoplasmic accumulation, is rapidly and transiently activated; however, its transcripts become unstable when they reach the cytoplasm. Our study reveals the dynamic localization of mRNAs between the nucleus and cytoplasm as an emerging feature in the temporal control of gene expression in response to nitrate treatment in Arabidopsis roots.

Asunto(s)

Arabidopsis , Núcleo Celular , Citoplasma , Regulación de la Expresión Génica de las Plantas , Nitratos , Raíces de Plantas , ARN Mensajero , Arabidopsis/genética , Arabidopsis/metabolismo , Nitratos/metabolismo , Nitratos/farmacología , Raíces de Plantas/metabolismo , Raíces de Plantas/genética , ARN Mensajero/genética , ARN Mensajero/metabolismo , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Regulación de la Expresión Génica de las Plantas/efectos de los fármacos , Proteínas de Arabidopsis/metabolismo , Proteínas de Arabidopsis/genética , Nitrato-Reductasa/metabolismo , Nitrato-Reductasa/genética

RESUMEN

The roots of plants play multiple functions that are essential for growth and development, including anchoring to the soil as well as water and nutrient acquisition. These underground organs exhibit the plasticity to modify their root system architecture in response to environmental cues, allowing adaptation to change in water and nutrient availability. In addition, roots enter in mutualistic interactions with soil microorganisms, for example, the root nodule symbiosis (RNS) established between a limited group of plants and nitrogen-fixing soil bacteria and the arbuscular mycorrhiza symbiosis involving most land plants and fungi of the Glomeromycetes phylum. In the past 20 years, genetic approaches allowed the identification and functional characterization of genes required for the specific programs of root development, root nodule, and arbuscular mycorrhiza symbioses. These genetic studies provided evidence that the program of the RNS recruited components of the arbuscular mycorrhiza symbiosis and the root developmental programs. The execution of these programs is strongly influenced by epigenetic changes-DNA methylation and histone post-translational modifications-that alter chromatin conformation modifying the expression of key genes. In this review, we summarize recent advances that highlight how DNA methylation and histone post-translational modifications, as well as chromatin remodeling factors and long noncoding RNAs, shape the root system architecture and allow the successful establishment of both root nodule and arbuscular mycorrhiza symbioses. We anticipate that the analysis of dynamic epigenetic changes and chromatin 3D structure in specific single cells or tissue types of root organs will illuminate our understanding of how root developmental and symbiotic programs are orchestrated, opening exciting questions and new perspectives to modulate agronomical and ecological traits linked to nutrient acquisition.

Asunto(s)

Epigénesis Genética , Raíces de Plantas , Simbiosis , Simbiosis/genética , Simbiosis/fisiología , Raíces de Plantas/microbiología , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/genética , Micorrizas/fisiología , Metilación de ADN/genética , Regulación de la Expresión Génica de las Plantas

RESUMEN

BACKGROUND: On tropical regions, phosphorus (P) fixation onto aluminum and iron oxides in soil clays restricts P diffusion from the soil to the root surface, limiting crop yields. While increased root surface area favors P uptake under low-P availability, the relationship between the three-dimensional arrangement of the root system and P efficiency remains elusive. Here, we simultaneously assessed allelic effects of loci associated with a variety of root and P efficiency traits, in addition to grain yield under low-P availability, using multi-trait genome-wide association. We also set out to establish the relationship between root architectural traits assessed in hydroponics and in a low-P soil. Our goal was to better understand the influence of root morphology and architecture in sorghum performance under low-P availability. RESULT: In general, the same alleles of associated SNPs increased root and P efficiency traits including grain yield in a low-P soil. We found that sorghum P efficiency relies on pleiotropic loci affecting root traits, which enhance grain yield under low-P availability. Root systems with enhanced surface area stemming from lateral root proliferation mostly up to 40 cm soil depth are important for sorghum adaptation to low-P soils, indicating that differences in root morphology leading to enhanced P uptake occur exactly in the soil layer where P is found at the highest concentration. CONCLUSION: Integrated QTLs detected in different mapping populations now provide a comprehensive molecular genetic framework for P efficiency studies in sorghum. This indicated extensive conservation of P efficiency QTL across populations and emphasized the terminal portion of chromosome 3 as an important region for P efficiency in sorghum. Increases in root surface area via enhancement of lateral root development is a relevant trait for sorghum low-P soil adaptation, impacting the overall architecture of the sorghum root system. In turn, particularly concerning the critical trait for water and nutrient uptake, root surface area, root system development in deeper soil layers does not occur at the expense of shallow rooting, which may be a key reason leading to the distinctive sorghum adaptation to tropical soils with multiple abiotic stresses including low P availability and drought.

Asunto(s)

Estudio de Asociación del Genoma Completo , Fósforo , Raíces de Plantas , Sitios de Carácter Cuantitativo , Sorghum , Sorghum/genética , Sorghum/metabolismo , Sorghum/crecimiento & desarrollo , Fósforo/metabolismo , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Raíces de Plantas/genética , Raíces de Plantas/anatomía & histología , Mapeo Cromosómico , Polimorfismo de Nucleótido Simple , Suelo/química , Fenotipo

RESUMEN

BACKGROUND: Soybean establishes a mutualistic interaction with nitrogen-fixing rhizobacteria, acquiring most of its nitrogen requirements through symbiotic nitrogen fixation. This crop is susceptible to water deficit; evidence suggests that its nodulation status-whether it is nodulated or not-can influence how it responds to water deficit. The translational control step of gene expression has proven relevant in plants subjected to water deficit. RESULTS: Here, we analyzed soybean roots' differential responses to water deficit at transcriptional, translational, and mixed (transcriptional + translational) levels. Thus, the transcriptome and translatome of four combined-treated soybean roots were analyzed. We found hormone metabolism-related genes among the differentially expressed genes (DEGs) at the translatome level in nodulated and water-restricted plants. Also, weighted gene co-expression network analysis followed by differential expression analysis identified gene modules associated with nodulation and water deficit conditions. Protein-protein interaction network analysis was performed for subsets of mixed DEGs of the modules associated with the plant responses to nodulation, water deficit, or their combination. CONCLUSIONS: Our research reveals that the stand-out processes and pathways in the before-mentioned plant responses partially differ; terms related to glutathione metabolism and hormone signal transduction (2 C protein phosphatases) were associated with the response to water deficit, terms related to transmembrane transport, response to abscisic acid, pigment metabolic process were associated with the response to nodulation plus water deficit. Still, two processes were common: galactose metabolism and branched-chain amino acid catabolism. A comprehensive analysis of these processes could lead to identifying new sources of tolerance to drought in soybean.

Asunto(s)

Glycine max , Raíces de Plantas , Transcriptoma , Glycine max/genética , Glycine max/fisiología , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Regulación de la Expresión Génica de las Plantas , Nodulación de la Raíz de la Planta/genética , Redes Reguladoras de Genes , Perfilación de la Expresión Génica , Deshidratación

RESUMEN

BACKGROUND: Phytophthora root rot, a major constraint in chile pepper production worldwide, is caused by the soil-borne oomycete, Phytophthora capsici. This study aimed to detect significant regions in the Capsicum genome linked to Phytophthora root rot resistance using a panel consisting of 157 Capsicum spp. genotypes. Multi-locus genome wide association study (GWAS) was conducted using single nucleotide polymorphism (SNP) markers derived from genotyping-by-sequencing (GBS). Individual plants were separately inoculated with P. capsici isolates, 'PWB-185', 'PWB-186', and '6347', at the 4-8 leaf stage and were scored for disease symptoms up to 14-days post-inoculation. Disease scores were used to calculate disease parameters including disease severity index percentage, percent of resistant plants, area under disease progress curve, and estimated marginal means for each genotype. RESULTS: Most of the genotypes displayed root rot symptoms, whereas five accessions were completely resistant to all the isolates and displayed no symptoms of infection. A total of 55,117 SNP markers derived from GBS were used to perform multi-locus GWAS which identified 330 significant SNP markers associated with disease resistance. Of these, 56 SNP markers distributed across all the 12 chromosomes were common across the isolates, indicating association with more durable resistance. Candidate genes including nucleotide-binding site leucine-rich repeat (NBS-LRR), systemic acquired resistance (SAR8.2), and receptor-like kinase (RLKs), were identified within 0.5 Mb of the associated markers. CONCLUSIONS: Results will be used to improve resistance to Phytophthora root rot in chile pepper by the development of Kompetitive allele-specific markers (KASP®) for marker validation, genomewide selection, and marker-assisted breeding.

Asunto(s)

Capsicum , Resistencia a la Enfermedad , Estudio de Asociación del Genoma Completo , Phytophthora , Enfermedades de las Plantas , Raíces de Plantas , Polimorfismo de Nucleótido Simple , Phytophthora/fisiología , Phytophthora/patogenicidad , Capsicum/genética , Capsicum/microbiología , Enfermedades de las Plantas/microbiología , Enfermedades de las Plantas/genética , Resistencia a la Enfermedad/genética , Raíces de Plantas/microbiología , Raíces de Plantas/genética , Genotipo

RESUMEN

Cassava root-rot incited by soil-borne pathogens is one of the major diseases that reduces root yield. Although the use of resistant cultivars is the most effective method of management, the genetic basis for root-rot resistance remains poorly understood. Therefore, our work analyzed the transcriptome of two contrasting genotypes (BRS Kiriris/resistant and BGM-1345/susceptible) using RNA-Seq to understand the molecular response and identify candidate genes for resistance. Cassava seedlings (resistant and susceptible to root-rot) were both planted in infested and sterilized soil and samples from Initial-time and Final-time periods, pooled. Two controls were used: (i) seedlings collected before planting in infested soil (absolute control) and, (ii) plants grown in sterilized soil (mock treatments). For the differentially expressed genes (DEGs) analysis 23.912 were expressed in the resistant genotype, where 10.307 were differentially expressed in the control treatment, 15 DEGs in the Initial Time-period and 366 DEGs in the Final Time-period. Eighteen candidate genes from the resistant genotype were related to plant defense, such as the MLP-like protein 31 and the peroxidase A2-like gene. This is the first model of resistance at the transcriptional level proposed for the cassava × root-rot pathosystem. Gene validation will contribute to screening for resistance of germplasm, segregating populations and/or use in gene editing in the pursuit to develop most promising cassava clones with resistance to root-rot.

Asunto(s)

Resistencia a la Enfermedad , Regulación de la Expresión Génica de las Plantas , Manihot , Enfermedades de las Plantas , Raíces de Plantas , Transcriptoma , Manihot/genética , Manihot/microbiología , Resistencia a la Enfermedad/genética , Raíces de Plantas/genética , Raíces de Plantas/microbiología , Enfermedades de las Plantas/genética , Enfermedades de las Plantas/microbiología , Perfilación de la Expresión Génica , Genotipo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Genes de Plantas

RESUMEN

Legume plants develop two types of root postembryonic organs, lateral roots and symbiotic nodules, using shared regulatory components. The module composed by the microRNA390, the Trans-Acting SIRNA3 (TAS3) RNA and the Auxin Response Factors (ARF)2, ARF3, and ARF4 (miR390/TAS3/ARFs) mediates the control of both lateral roots and symbiotic nodules in legumes. Here, a transcriptomic approach identified a member of the Lateral Organ Boundaries Domain (LBD) family of transcription factors in Medicago truncatula, designated MtLBD17/29a, which is regulated by the miR390/TAS3/ARFs module. ChIP-PCR experiments evidenced that MtARF2 binds to an Auxin Response Element present in the MtLBD17/29a promoter. MtLBD17/29a is expressed in root meristems, lateral root primordia, and noninfected cells of symbiotic nodules. Knockdown of MtLBD17/29a reduced the length of primary and lateral roots and enhanced lateral root formation, whereas overexpression of MtLBD17/29a produced the opposite phenotype. Interestingly, both knockdown and overexpression of MtLBD17/29a reduced nodule number and infection events and impaired the induction of the symbiotic genes Nodulation Signaling Pathway (NSP) 1 and 2. Our results demonstrate that MtLBD17/29a is regulated by the miR390/TAS3/ARFs module and a direct target of MtARF2, revealing a new lateral root regulatory hub recruited by legumes to act in the root nodule symbiotic program.

Asunto(s)

Medicago truncatula , Proteínas de Plantas , Nodulación de la Raíz de la Planta , Raíces de Plantas , Factores de Transcripción , Regulación de la Expresión Génica de las Plantas , Técnicas de Silenciamiento del Gen , Ácidos Indolacéticos/metabolismo , Medicago truncatula/genética , Medicago truncatula/crecimiento & desarrollo , Medicago truncatula/microbiología , MicroARNs/genética , MicroARNs/metabolismo , Proteínas de Plantas/metabolismo , Proteínas de Plantas/genética , Nodulación de la Raíz de la Planta/genética , Raíces de Plantas/genética , Raíces de Plantas/crecimiento & desarrollo , Regiones Promotoras Genéticas/genética , Nódulos de las Raíces de las Plantas/genética , Nódulos de las Raíces de las Plantas/crecimiento & desarrollo , Simbiosis/genética , Factores de Transcripción/metabolismo , Factores de Transcripción/genética

RESUMEN

Among plant-parasitic nematodes, root-knot nematodes (RKN), Meloidogyne spp., are the most important parasite infecting economically important crops globally and causing severe losses in crop production. The use of efficient nematode control methods against these parasites depends upon their correct detection in roots and soil samples. Currently, the use of integrated identification methods, including biochemical, molecular, and morphological-based characters, is preferred. But the techniques using morphology and phylogenetic analysis are time-consuming and not suitable for routine analysis. They have only been used for studies of cryptic species, which were identified using integrative taxonomy. Here we describe the enzymatic and molecular-based methods that have successfully been used in Brazil for more than 25 years in the Nematology Lab at Embrapa Genetic Resources and Biotechnology for routine analysis. This technique is a combination of isozyme esterase profiling and molecular markers, with the aim of having a rapid and correct diagnosis of Meloidogyne spp. populations from field and greenhouse.

Asunto(s)

Raíces de Plantas , Tylenchoidea , Animales , Filogenia , Raíces de Plantas/genética , Raíces de Plantas/parasitología , Tylenchoidea/genética , Brasil

RESUMEN

Cysteine-rich receptor-like kinases (CRKs) are a type of receptor-like kinases (RLKs) that are important for pathogen resistance, extracellular reactive oxygen species (ROS) signaling, and programmed cell death in plants. In a previous study, we identified 46 CRK family members in the Phaseolus vulgaris genome and found that CRK12 was highly upregulated under root nodule symbiotic conditions. To better understand the role of CRK12 in the Phaseolus-Rhizobia symbiotic interaction, we functionally characterized this gene by overexpressing (CRK12-OE) and silencing (CRK12-RNAi) it in a P. vulgaris hairy root system. We found that the constitutive expression of CRK12 led to an increase in root hair length and the expression of root hair regulatory genes, while silencing the gene had the opposite effect. During symbiosis, CRK12-RNAi resulted in a significant reduction in nodule numbers, while CRK12-OE roots showed a dramatic increase in rhizobial infection threads and the number of nodules. Nodule cross sections revealed that silenced nodules had very few infected cells, while CRK12-OE nodules had enlarged infected cells, whose numbers had increased compared to controls. As expected, CRK12-RNAi negatively affected nitrogen fixation, while CRK12-OE nodules fixed 1.5 times more nitrogen than controls. Expression levels of genes involved in symbiosis and ROS signaling, as well as nitrogen export genes, supported the nodule phenotypes. Moreover, nodule senescence was prolonged in CRK12-overexpressing roots. Subcellular localization assays showed that the PvCRK12 protein localized to the plasma membrane, and the spatiotemporal expression patterns of the CRK12-promoter::GUS-GFP analysis revealed a symbiosis-specific expression of CRK12 during the early stages of rhizobial infection and in the development of nodules. Our findings suggest that CRK12, a membrane RLK, is a novel regulator of Phaseolus vulgaris-Rhizobium tropici symbiosis.

Asunto(s)

Phaseolus , Rhizobium tropici , Rhizobium , Simbiosis/genética , Rhizobium tropici/genética , Rhizobium tropici/metabolismo , Phaseolus/metabolismo , Especies Reactivas de Oxígeno/metabolismo , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Rhizobium/metabolismo , Fijación del Nitrógeno/genética , Nódulos de las Raíces de las Plantas/metabolismo

RESUMEN

A continuum from stem to transit-amplifying to a differentiated cell state is a common theme in multicellular organisms. In the plant root apical meristem (RAM), transit-amplifying cells are organized into two domains: cells from the proliferation domain (PD) are displaced to the transition domain (TD), suggesting that both domains are necessarily coupled. Here, we show that in the Arabidopsis thaliana mto2-2 mutant, in which threonine (Thr) synthesis is affected, the RAM lacks the PD. Through a combination of cell length profile analysis, mathematical modeling and molecular markers, we establish that the PD and TD can be uncoupled. Remarkably, although the RAM of mto2-2 is represented solely by the TD, the known factors of RAM maintenance and auxin signaling are expressed in the mutant. Mathematical modeling predicts that the stem cell niche depends on Thr metabolism and that, when disturbed, the normal continuum of cell states becomes aborted.

Asunto(s)

Proteínas de Arabidopsis , Arabidopsis , Meristema/genética , Meristema/metabolismo , Proteínas de Arabidopsis/genética , Proteínas de Arabidopsis/metabolismo , Treonina/genética , Arabidopsis/genética , Arabidopsis/metabolismo , Mutación/genética , Proliferación Celular/genética , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Regulación de la Expresión Génica de las Plantas

Asunto(s)

Amigos , Redes Reguladoras de Genes , Regulación de la Expresión Génica de las Plantas , Humanos , Raíces de Plantas/genética

RESUMEN

Carrot (Daucus carota) is a useful plant model for the study of carotenoid biosynthesis, specifically in roots which are enriched in carotenoids. Carrot genome and transcriptome sequences, complemented by optimized methods for carrot transformation, contribute to a comprehensive toolbox for exploring pathway regulation. To expand the repertoire of tools available for the study of D. carota, we present protocols for the isolation of protoplasts from D. carota cell suspension cultures and polyethylene glycol (PEG)-mediated transformation. To obtain carrot protoplasts, in vitro somatic embryogenesis from epicotyls is induced. The somatic embryogenic tissue that develops is transferred to liquid medium to obtain a suspension of cells which are homogenized and incubated with cell-wall degrading enzymes to release protoplasts. For transfection, protoplasts are incubated with a plasmid encoding a protein of interest prior to examination of protein localization by light microscopy. As an example, we demonstrate nuclear localization of a carrot transcription factor, DcAREB3.

Asunto(s)

Daucus carota , Carotenoides/metabolismo , Daucus carota/genética , Daucus carota/metabolismo , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Protoplastos/metabolismo

RESUMEN

Meloidogyne javanica is among the most important nematodes that damage soybean, and although genetic resistance is the ideal control measure, there are few cultivars described as resistant among those recommended for southern Brazil. The objective of this work was to evaluate the reaction of soybean cultivars to M. javanica. The inoculum of nematodes (Est. J3) was obtained from soybean plants and inoculated into tomato plants cultivar "Santa Cruz". Thirty-seven soybean cultivars widely used in the South, Southeast and Midwest of Brazil were used in the experiment. For each plant a suspension of 5,000 eggs + juveniles of second stage of M. javanica was inoculated into a sterile soil hole in 2-liter pots with six replications. The evaluation of root weight, number of galls, number of nematodes was 60 days after M. javanica inoculation. The results were subjected to analysis of variance, and the averages of each treatment were compared to each other by the Scott-Knott cluster test at 5% probability. Even though M. javanica presented RF> 1.00 in all soybean genotypes tested, different levels of susceptibility were observed. Thus, the lowest reproduction of the root-knot nematode was observed in M ​​5947 IPRO, HO AMAMBAY IPRO, BMX GARRA IPRO and FPS ATALANTA.

Asunto(s)

Fabaceae , Tylenchoidea , Animales , Genotipo , Raíces de Plantas/genética , Reproducción/genética , Glycine max/genética , Tylenchoidea/genética

RESUMEN

Understanding how roots modulate development under varied irrigation or rainfall is crucial for development of climate-resilient crops. We established a toolbox of tagged rice lines to profile translating mRNAs and chromatin accessibility within specific cell populations. We used these to study roots in a range of environments: plates in the lab, controlled greenhouse stress and recovery conditions, and outdoors in a paddy. Integration of chromatin and mRNA data resolves regulatory networks of the following: cycle genes in proliferating cells that attenuate DNA synthesis under submergence; genes involved in auxin signaling, the circadian clock, and small RNA regulation in ground tissue; and suberin biosynthesis, iron transporters, and nitrogen assimilation in endodermal/exodermal cells modulated with water availability. By applying a systems approach, we identify known and candidate driver transcription factors of water-deficit responses and xylem development plasticity. Collectively, this resource will facilitate genetic improvements in root systems for optimal climate resilience.

Asunto(s)

Oryza , Cromatina/metabolismo , Regulación de la Expresión Génica de las Plantas , Redes Reguladoras de Genes , Oryza/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raíces de Plantas/genética , Raíces de Plantas/metabolismo , Agua/metabolismo

RESUMEN

The development of a symbiotic nitrogen-fixing nodule in legumes involves infection and organogenesis. Infection begins when rhizobia enter a root hair through an inward structure, the infection thread (IT), which guides the bacteria towards the cortical tissue. Concurrently, organogenesis takes place by inducing cortical cell division (CCD) at the infection site. Genetic analysis showed that both events are well-coordinated; however, the dynamics connecting them remain to be elucidated. To visualize the crossroads between IT and CCD, we benefited from the fact that, in Phaseolus vulgaris nodulation, where the first division occurs in subepidermal cortical cells located underneath the infection site, we traced a Rhizobium etli strain expressing DsRed, the plant cytokinesis marker YFP-PvKNOLLE, a nuclear stain and cell wall auto-fluorescence. We found that the IT exits the root hair to penetrate an underlying subepidermal cortical (S-E) cell when it is concluding cytokinesis.

Asunto(s)

Phaseolus , Rhizobium , División Celular , Phaseolus/microbiología , Proteínas de Plantas/genética , Nodulación de la Raíz de la Planta , Raíces de Plantas/genética , Rhizobium/genética , Nódulos de las Raíces de las Plantas/microbiología , Simbiosis/genética

RESUMEN

The identification of genomic regions associated with root traits and the genomic prediction of untested genotypes can increase the rate of genetic gain in maize breeding programs targeting roots traits. Here, we combined two maize association panels with different genetic backgrounds to identify single nucleotide polymorphisms (SNPs) associated with root traits, and used a genome-wide association study (GWAS) and to assess the potential of genomic prediction for these traits in maize. For this, we evaluated 377 lines from the Ames panel and 302 from the Backcrossed Germplasm Enhancement of Maize (BGEM) panel in a combined panel of 679 lines. The lines were genotyped with 232 460 SNPs, and four root traits were collected from 14-day-old seedlings. We identified 30 SNPs significantly associated with root traits in the combined panel, whereas only two and six SNPs were detected in the Ames and BGEM panels, respectively. Those 38 SNPs were in linkage disequilibrium with 35 candidate genes. In addition, we found higher prediction accuracy in the combined panel than in the Ames or BGEM panel. We conclude that combining association panels appears to be a useful strategy to identify candidate genes associated with root traits in maize and improve the efficiency of genomic prediction.

Asunto(s)

Estudio de Asociación del Genoma Completo , Zea mays , Genómica , Fenotipo , Fitomejoramiento , Raíces de Plantas/genética , Polimorfismo de Nucleótido Simple , Plantones/genética , Zea mays/genética

RESUMEN

Root hair cells are important sensors of soil conditions. They grow towards and absorb water-soluble nutrients. This fast and oscillatory growth is mediated by continuous remodeling of the cell wall. Root hair cell walls contain polysaccharides and hydroxyproline-rich glycoproteins, including extensins (EXTs). Class-III peroxidases (PRXs) are secreted into the apoplastic space and are thought to trigger either cell wall loosening or polymerization of cell wall components, such as Tyr-mediated assembly of EXT networks (EXT-PRXs). The precise role of these EXT-PRXs is unknown. Using genetic, biochemical, and modeling approaches, we identified and characterized three root-hair-specific putative EXT-PRXs, PRX01, PRX44, and PRX73. prx01,44,73 triple mutation and PRX44 and PRX73 overexpression had opposite effects on root hair growth, peroxidase activity, and ROS production, with a clear impact on cell wall thickness. We use an EXT fluorescent reporter with contrasting levels of cell wall insolubilization in prx01,44,73 and PRX44-overexpressing background plants. In this study, we propose that PRX01, PRX44, and PRX73 control EXT-mediated cell wall properties during polar expansion of root hair cells.

Asunto(s)

Proteínas de Arabidopsis , Arabidopsis , Arabidopsis/genética , Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/genética , Pared Celular , Peroxidasas/genética , Raíces de Plantas/genética

RESUMEN

Cowpea [Vigna unguiculata (L.) Walp.] is one of the most tolerant legume crops to drought and salt stresses. WRKY transcription factor (TF) family members stand out among plant transcriptional regulators related to abiotic stress tolerance. However, little information is currently available on the expression of the cowpea WRKY gene family (VuWRKY) in response to water deficit. Thus, we analyzed genomic and transcriptomic data from cowpea to identify VuWRKY members and characterize their structure and transcriptional response under root dehydration stress. Ninety-two complete VuWRKY genes were found in the cowpea genome based on their domain characteristics. They were clustered into three groups: I (15 members), II (58), and III (16), while three genes were unclassified. Domain analysis of the encoded proteins identified four major variants of the conserved heptapeptide motif WRKYGQK. In silico analysis of VuWRKY gene promoters identified eight candidate binding motifs of cis-regulatory elements, regulated mainly by six TF families associated with abiotic stress responses. Ninety-seven VuWRKY modulated splicing variants associated with 55 VuWRKY genes were identified via RNA-Seq analysis available at the Cowpea Genomics Consortium (CpGC) database. qPCR analyses showed that 22 genes are induced under root dehydration, with VuWRKY18, 21, and 75 exhibiting the most significant induction levels. Given their central role in activating signal transduction cascades in abiotic stress response, the data provide a foundation for the targeted modification of specific VuWRKY family members to improve drought tolerance in this important climate-resilient legume in the developing world and beyond.

Asunto(s)

Perfilación de la Expresión Génica/métodos , Genómica/métodos , Factores de Transcripción/química , Factores de Transcripción/genética , Vigna/genética , Empalme Alternativo , Secuencias de Aminoácidos , Mapeo Cromosómico , Sequías , Regulación de la Expresión Génica de las Plantas , Familia de Multigenes , Proteínas de Plantas/química , Proteínas de Plantas/genética , Raíces de Plantas/genética , Regiones Promotoras Genéticas , Dominios Proteicos , RNA-Seq , Estrés Fisiológico

RESUMEN

Using tolerant genotypes and the correct use of fertilizers can mitigate the negative effect of elevated Cu levels in the growing medium. In this context, the study aimed to evaluate the effects of excess Cu in the root system and the effectiveness of phosphorus (P) in minimizing the phytotoxicity of Cu in three genotypes: IAC 572 [(Vitis riparia x V. rupestris) x V. caribaea], Magnolia (V. rotundifolia) and Paulsen 1103 (V. berlandieri x V. rupestris). The plants were grown in nutrient solutions and were supplemented with the following treatments: 0.3 µM Cu (Control), 60 µM Cu (Cu) and 60 µM Cu and 62 mg L-1 P (Cu + P). Root samples were sectioned for microscopy analyses, and the shoot lengths, shoot and root dry matter, relative growth rates (RGR) and tissue nutrient contents were also evaluated. The roots of the genotypes that were cultivated with high Cu concentrations produced greater numbers of branches and larger diameters, except for Magnolia genotype that was cultivated in a Cu + P solution, which had an organization similar to the control. Excess Cu caused accumulations of phenolic compounds and decreased shoot lengths, dry matter and RGR in the genotypes. In the treatments with excess Cu, there were increases in this element in the tissues, but P decreased the metal concentrations in Magnolia roots. Therefore, Cu accumulations alter the root system development patterns, growth parameters and tissue nutrient contents in the studied genotypes. Magnolia has a higher tolerance and is also the only genotype for which the use of P has been shown to be effective.

Asunto(s)

Vitis , Genotipo , Fósforo , Raíces de Plantas/genética , Vitis/genética