Biology subjects

Muday, G. K.

Publications and source records attributed to Muday, G. K..

7 recordsLinked to original sources

bioRxiv2024

Enhanced pollen tube performance at high temperature contributes to thermotolerant fruit production in tomato.

Rising temperature extremes during critical reproductive periods threaten the yield of major grain and fruit crops. Flowering plant reproduction depends on development of sufficient numbers of pollen grains and on their ability to generate a cellular extension, the pollen tube, which elongates through the pistil to deliver sperm cells to female gametes for double fertilization. These critical phases of the life cycle are sensitive to temperature and limit productivity under high temperature (HT). Previous studies have investigated the effects of HT on pollen development, but little is known about how HT applied during the pollen tube growth phase affects fertility. Here, we used tomato as a model fruit crop to determine how HT affects the pollen tube growth phase, taking advantage of cultivars noted for fruit production in exceptionally hot growing seasons. We found that exposure to HT solely during the pollen tube growth phase limits fruit biomass and seed set more significantly in thermosensitive cultivars than in thermotolerant cultivars. Importantly, we found that pollen tubes from the thermotolerant Tamaulipas cultivar have enhanced growth in vivo and in vitro under HT. Analysis of the pollen tube transcriptomes response to HT allowed us to develop hypotheses for the molecular basis of cellular thermotolerance in the pollen tube and we define two response modes (enhanced induction of stress responses, and higher basal levels of growth pathways repressed by heat stress) associated with reproductive thermotolerance. Importantly, we define key components of the pollen tube stress response identifying enhanced ROS homeostasis and pollen tube callose synthesis and deposition as important components of reproductive thermotolerance in Tamaulipas. Our work identifies the pollen tube growth phase as a viable target to enhance reproductive thermotolerance and delineates key pathways that are altered in crop varieties capable of fruiting under HT conditions. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=95 SRC="FIGDIR/small/606234v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@25e5acorg.highwire.dtl.DTLVardef@98fb1org.highwire.dtl.DTLVardef@1b8b9cborg.highwire.dtl.DTLVardef@adcca4_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2024

Ethylene Receptor Gain- and Loss-of-function Mutants Reveal an ETR1-dependent Transcriptional Network in Roots

In Arabidopsis, a family of five receptors mediates ethylene responses in roots, with Ethylene Response 1 (ETR1) controlling increases in root hair proliferation and decreases in lateral root formation. To define the ETR1-dependent gene regulatory network (GRN) controlling root development, we profiled the root transcriptome from Col-0 and the etr1-3 gain-of-function and etr1-7 loss-of-function mutants in the presence and absence of ethylene or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC). We identified 4,522 differentially expressed (DE) transcripts in Col-0 roots with altered abundance in response to ethylene and/or ACC treatment, with larger magnitude changes induced by ethylene. These included 553 DE transcripts that were ETR1 dependent, defined by a lack of response to treatment with ethylene and/or ACC in ethylene-insensitive etr1-3 and constitutively altered in etr1-7 in the presence and absence of treatment relative to time-0 Col-0. Within these ETR1-dependent transcripts were ethylene biosynthesis genes and transcription factors. ACC OXIDASE 2 (ACO2) and ACO3 convert ACC to ethylene and were ETR1-dependent, and ACO-promoter-driven reporter fusions were ACC regulated in root tissues in appropriate locations to control root development, with ACO5 localized to root hairs. Abundance of ETR1-dependent transcripts that were predicted to encode transcription factors and ACOs were examined in Col-0 and an ein3eil1 mutant with and without ACC treatment, suggesting the ETR1 and EIN3/EIL1 canonical ethylene signaling pathway regulated some, but not all, of these transcriptional responses. Together, these findings reveal features of an ETR1-dependent GRN that controls both ethylene synthesis and root growth and development. One sentence summaryTranscriptional responses in etr1 LOF and GOF mutants reveal an ethylene-mediated ETR1- and EIN3 dependent gene regulatory network that modulates ethylene signaling and synthesis and root development.

plant biology↗

bioRxiv2023

Flavonols improve thermotolerance in tomato pollen during germination and tube elongation by maintaining ROS homeostasis

Elevated temperatures impair pollen performance and reproductive success, resulting in lower crop yields. The Solanum lycopersicum anthocyanin reduced (are) mutant has a FLAVANONE 3 HYDROXYLASE (F3H) gene mutation resulting in impaired synthesis of flavonol antioxidants. The are mutant has reduced pollen performance and seed set relative to the VF36 parental line, which is accentuated at elevated temperatures. Transformation of are with the wild-type F3H gene, or chemical complementation with flavonols, prevented temperature-dependent ROS accumulation in pollen and reversed ares reduced viability, germination, and tube elongation to VF36 levels. VF36 transformed with an F3H overexpression construct prevented temperature driven ROS increases and impaired pollen performance, revealing thermotolerance results from elevated flavonol synthesis. Although stigmas of are had reduced flavonols and elevated ROS, the growth of are pollen tubes were similarly impaired in both are and VF36 pistils. RNA-Seq was performed at optimal and stress temperatures in are, VF36, and the VF36 F3H overexpression line at multiple timepoints across pollen tube elongation. Differentially expressed gene numbers increased with duration of elevated temperature in all genotypes, with the largest number in are. These findings suggest potential agricultural interventions to combat the negative effects of heat-induced ROS in pollen that leads to reproductive failure. One sentence summaryFlavonol antioxidants reduce the negative impacts of elevated temperatures on pollen performance by reducing levels of heat induced reactive oxygen species and modulation of heat-induced changes in the pollen transcriptome.

plant biology↗

bioRxiv2022

Partitioned Local Depth analysis of time course transcriptomic data reveals elaborate community structure

Transcriptome studies that provide temporal information are valuable for identifying groups of similarly-behaving transcripts, giving insight into overarching gene regulatory networks. Nevertheless, inferring transcriptional networks from time series data is challenging, in part because it is difficult to holistically consider both local relationships and global structure of these complex and overlapping transcriptional responses. To address this need, we employed the Partitioned Local Depth (PaLD) method to examine four time series transcriptomic datasets generated using the model plant Arabidopsis thaliana. Here, we provide a self-contained description of the method and demonstrate how it can be used to make predictions about gene regulatory networks based on time series data. The analysis provides a global network representation of the data from which graph partitioning methods and neighborhood analysis can reveal smaller, more well-defined groups of like-responding transcripts. These groups of transcripts that change in response to hormone treatment (e.g., auxin or ethylene) or high salinity were demonstrated to be enriched in common biological function and/or binding of transcription factors that were not identified with prior analyses of this data using other clustering and inference methodologies. These results reveal the ability of PaLD to generate predictions about gene regulatory networks using time series transcriptomic data, which can be of value to the systems biology community.

systems biology↗

bioRxiv2022

Abscisic Acid Increases Hydrogen Peroxide in Multiple Subcellular Compartments to Drive Stomatal Closure

Abscisic acid (ABA) drives stomatal closure to minimize water loss due to transpiration in response to drought. We examined the subcellular location of ABA increased accumulation of reactive oxygen species (ROS) in guard cells that drive stomatal closure. ABA-dependent increases in fluorescence of the generic ROS sensor, dichlorofluorescein (DCF), were observed in mitochondria, chloroplasts, cytosol, and nuclei. The ABA response in all these locations were lost in an ABA-insensitive quintuple receptor mutant. The ABA-increased fluorescence in mitochondria of both DCF and an H2O2-selective probe, Peroxy Orange 1 (PO1), colocalized with Mitotracker Red. ABA treatment of guard cells transformed with the genetically-encoded H2O2 reporter targeted to the cytoplasm (roGFP2-Orp1), or mitochondria (mt-roGFP2-Orp1), revealed H2O2 increases. Consistent with mitochondrial ROS changes functioning in stomatal closure, we found that guard cells of a mutant with mitochondrial defects, abo6, have elevated ABA-induced ROS in mitochondria and enhanced stomatal closure. These effects were phenocopied with rotenone, which increased mitochondrial ROS. In contrast, the mitochondrially targeted antioxidant, MitoQ, dampened ABA effects on mitochondrial ROS accumulation and stomatal closure in Col-0 and reversed the guard cell closure phenotype of the abo6 mutant. ABA-induced ROS accumulation in guard cell mitochondria was lost in mutants in genes encoding Respiratory Burst Oxidase Homolog (RBOH) enzymes and reduced by treatment with the RBOH inhibitor VAS2870, consistent with RBOH machinery acting in ABA-increased ROS in guard cell mitochondria. These results demonstrate that ABA elevates H2O2 accumulation in guard cell mitochondria to promote stomatal closure. One sentence summaryGenetically encoded biosensors and chemical probes revealed ABA-dependent increases in hydrogen peroxide, a reactive oxygen species with signaling activity, in guard cell cytoplasm and mitochondria.

plant biology↗

bioRxiv2021

Ethylene signaling increases reactive oxygen species accumulation to drive root hair initiation in Arabidopsis thaliana

Root hair initiation is a highly regulated aspect of root development. The plant hormone, ethylene, and its precursor, 1-amino-cyclopropane-1-carboxylic acid (ACC), induce formation and elongation of root hairs. Using confocal microscopy paired with redox biosensors and dyes, we demonstrated that treatments that elevate ethylene levels led to increased hydrogen peroxide accumulation in hair cells prior to root hair formation. In two ethylene-insensitive mutants, etr1-3 and ein3/eil1, there was no increase in root hair number or ROS accumulation. Conversely, etr1-7, a constitutive ethylene signaling receptor mutant, has increased root hair formation and ROS accumulation like ethylene-treated Col-0 seedlings. The caprice and werewolf transcription factor mutants have decreased and elevated ROS levels, which are correlated with levels of root hair initiation. The rhd2-6 mutant, with a defect in the gene encoding a ROS synthesizing Respiratory Burst Oxidase Homolog C (RBOHC) and the prx44-2 mutant defective in a class III peroxidase, showed impaired ethylene-dependent ROS synthesis and root hair formation and EIN3/EIL1 dependent transcriptional regulation. Together, these results indicate that ethylene increases ROS accumulation through RBOHC and PRX44 to drive root hair formation. SUMMARY STATEMENTThe gaseous hormone ethylene increases root hair initiation by elevating reactive oxygen species (ROS) in trichoblast cells. Genetic and biochemical approaches identified ethylene-regulated ROS producing enzymes that drive root hair initiation.

plant biology↗

bioRxiv2020

Flavonols modulate lateral root emergence by scavenging reactive oxygen species in Arabidopsis thaliana

Flavonoids are plant-specific antioxidant compounds that modulate plant development, which include flavonols and anthocyanins subclasses. In Arabidopsis thaliana, mutants in genes encoding each step in the flavonoid biosynthetic pathway have been isolated. We used these mutants to examine the role of flavonols in initiation and emergence of lateral roots and asked whether this regulation occurs through scavenging ROS. The tt4 mutants have a defect in the first committed step of flavonoid biosynthesis and have increased lateral root emergence. This phenotype was reversed by both genetic and chemical complementation. Using these flavonoid biosynthetic mutants, we eliminated roles for anthocyanins and the flavonols, quercetin and isorhamnetin, in controlling lateral root development. The tt7-2 mutant has a defect in a branchpoint enzyme blocking quercetin biosynthesis that led to elevated levels of kaempferol and reduced lateral roots. Kaempferol accumulated within lateral root primordia and was significantly increased in tt7-2. Thee data are consistent with kaempferol acting as a negative regulator of lateral root emergence. We examined ROS accumulation above and within the primordia using a general ROS sensor and identified increased signal above the primordia of the tt4 and tt7-2 mutants compared to wild type. Using a superoxide specific sensor, we detected a decrease in signal within the primordia of tt7-2, but not the tt4 mutant, compared to wild type. Together, these results support a model in which increased level of kaempferol in tt7-2 leads to a reduction in superoxide concentration in the lateral root primordia thereby reducing ROS-stimulated lateral root emergence.

plant biology↗