Browsing by Author "Senthil-Kumar, Muthappa"

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Abiotic stress impact on the interaction between Macrophomina phaseolina and crop plants
(Springer Nature Publishing AG, 2024) Ranjan, Shubhashish; Mirchandani, Rishabh; Senthil-Kumar, Muthappa
Macrophomina phaseolina (Tassi.) Goid is an emerging pathogen that causes diseases like dry root rot and charcoal rot in more than 100 plant families. Abiotic stresses such as drought, salinity, and heat exacerbate this fungal effect and predispose crops to pathogen attacks. Importantly, these combined stresses lead to significant crop yield losses under field conditions. In this, we review the interaction between the devastating pathogen M. phaseolina and several abiotic stresses that are more likely to occur in scenarios of climate change. Drought, heat, and salinity are the major stresses that interact with M. phaseolina in the field. We discuss several field studies, unique physiological and molecular responses, and their mechanisms of control in response to combined stress. The net effect of these interactions depends on a multitude of factors; thus, these interactions modify the impact of biotic stresses on plants by altering their susceptibility. The aim of this review is to provide an overview of what is currently known about M. phaseolina and abiotic stress interactions, as well as several other edaphic factors that interact with plants. We briefly discuss the role of drought, salinity, heat stress, and edaphic factors (such as pH, N, P, K, etc.) that influence pathogen infection in plants. Furthermore, we discuss possible management strategies to combat crop loss due to combined stress. Thus, we suggest the future aspect of combined stress breeding, along with the use of multi-omics techniques and genome editing approaches, to develop cultivars that exhibit stability in a combined stress environment.
Advances in plant gene silencing methods
(Springer, 2015) Pandey, Prachi; Senthil-Kumar, Muthappa; Mysore, Kirankumar S.
Understanding molecular mechanisms of transcriptional and posttranscriptional gene silencing pathways in plants over the past decades has led to development of tools and methods for silencing a target gene in various plant species. In this review chapter, both the recent understanding of molecular basis of gene silencing pathways and advances in various widely used gene silencing methods are compiled. We also discuss the salient features of the different methods like RNA interference (RNAi) and virus-induced gene silencing (VIGS) and highlight their advantages and disadvantages. Gene silencing technology is constantly progressing as reflected by rapidly emerging new methods. A succinct discussion on the recently developed methods like microRNA-mediated virus-induced gene silencing (MIR-VIGS) and microRNA-induced gene silencing (MIGS) is also provided. One major bottleneck in gene silencing approaches has been the associated off-target silencing. The other hurdle has been the lack of a universal approach that can be applied to all plants. For example, we face hurdles like incompatibility of VIGS vectors with the host and inability to use MIGS for plant species which are not easily transformable. However, the overwhelming research in this direction reflects the scope for overcoming the short comings of gene silencing technology.
An artificial neural network–based deep learning model to predict combined stress impact and interaction in plants
(John Wiley & Sons, 2026) Priya, Piyush; Pandey, Prachi; Jain, Rubi; Kandpal, Manu; Jain, Shradha; Chaudhury, Rim; Ramegowda, Venkategowda; Senthil-Kumar, Muthappa
Premise: Plants are frequently exposed to combinations of abiotic and biotic stresses that pose a greater threat to yield and productivity than individual stresses. However, knowledge of the impact of many stress combinations in numerous plants is limited due to the lack of experimental data, which could take decades to generate. To overcome this limitation, we utilized existing literature data from various plant species and stress combinations to derive biological inferences, thereby gaining a comprehensive understanding of plant responses through a computational tool. Methods: Public databases were used to gather literature on the impact of various abiotic and biotic stress combinations. Then, a composite artificial neural network (ANN)–based multi-target classification and regression deep learning model was developed using machine learning algorithms. Results: The model predicted the impact of stress interactions in plants, including the morphological parameters affected and percentage changes in those parameters, with an overall accuracy of 76.33%. Predicted reductions in yield were validated in rice under combined drought and heat stress. Discussion: The ANN-based model developed in this study is a valuable resource for plant researchers seeking to understand the impact of stress combinations. The tool can make use of multivariate and complex combined stress datasets.
AtGBF3 confers tolerance to Arabidopsis thaliana against combined drought and Pseudomonas syringae stress
(Elsevier B.V., 2019) Dixit, Sandeep Kumar; Gupta, Aarti; Fatima, Urooj; Senthil-Kumar, Muthappa
In field conditions, plants are often exposed to a combination of abiotic and biotic stresses, for instance, drought and pathogen infection. Transcriptome studies on Arabidopsis thaliana and other plants under individual and combined drought and pathogen stresses have unveiled the activation of shared molecular defense mechanisms. These shared plant responses are characterized by commonly regulated genes under both individual as well as combined stresses. Therefore, the identification of commonly regulated genes during individual and combined stress conditions can reveal plant responses towards combined stress. Available transcriptome studies on combined-stressed plants have hinted at G-Box Binding Factor 3 (GBF3) as one of the regulatory components of the shared response. However, the mechanistic understanding of the role of AtGBF3 under combined drought and pathogen stress is not yet decoded. In the current study, we used genetic approaches to identify the role of AtGBF3 in conferring tolerance to individual and combined drought and pathogen stress. Atgbf3 mutant plants showed increased susceptibility, while AtGBF3-overexpressing plants were tolerant under individual and combined drought and Pseudomonas syringae pv. tomato infection stresses as compared to wild-type plants. We further analyzed the global transcriptome of Atgbf3 mutant plants under combined stress to identify its downstream targets. We also established a high-throughput method to apply combined polyethylene glycol and pathogen stress on Murashige and Skoog medium-grown plants to further validate the role of AtGBF3 in combined stress.
ath-miR164c influences plant responses to the combined stress of drought and bacterial infection by regulating proline metabolism
(Elsevier B.V., 2020) Gupta, Aarti; Patil, Mahesh; Qamar, Aarzoo; Senthil-Kumar, Muthappa
Plants under combined stresses exhibit a prominent shift in molecular responses compared with plants exposed to the same stresses independently. Profiling responses to individual and combined stressors at the gene expression level have identified several genes with intersecting responses to these stressors. However, the upstream regulators at the intersection of plant responses to individual and combined stresses are not known. Here, using the transcriptome of Arabidopsis thaliana under individual and combined drought and Pseudomonas syringae infection, we identified several genes whose expression overlaps between individual and combined stresses. To study the key regulator of such an overlapping gene, we predicted that the expression of 1-Pyrroline-5-carboxylate synthase 1 (AtP5CS1) is regulated by ath-miR164c at post-transcriptional level. Our results from the stem-loop RT-PCR based expression analysis revealed significant downregulation of ath-miR164c in response to P. syringae infection under both well-irrigated (pathogen only) and drought stress (combined stress) conditions. Furthermore, an Arabidopsis loss-of-function mutant of the miRNA ath-miR164c exhibited resistance to pathogen infection under combined stress, unlike the wild-type plants, implicating the role of ath-miR164c in regulating plant immunity. AtP5CS1 gene expression and proline accumulation were enhanced in the ath-miR164c mutant plants relative to the wild-type plants, demonstrating that ath-miR164c regulates AtP5CS1 of the proline biosynthesis pathway, which was also validated by 5’RLM-RACE results. This miRNA-mediated modulation of AtP5CS1 gene expression under combined stress fills crucial gaps in identifying the key convergent players in the current understanding of plant stress responses.
AtSWEET11 and AtSWEET12 transporters function in tandem to modulate sugar flux in plants
(John Wiley & Sons, 2023) Fatima, Urooj; Balasubramaniam, D.; Khan, Wajahat Ali; Kandpal, Manu; Vadassery, Jyothilakshmi; Arockiasamy, Arulandu; Senthil-Kumar, Muthappa
The sugar will eventually be exported transporter (SWEET) members in Arabidopsis, AtSWEET11 and AtSWEET12 are the important sucrose efflux transporters that act synergistically to perform distinct physiological roles. These two transporters are involved in apoplasmic phloem loading, seed filling, and sugar level alteration at the site of pathogen infection. Here, we performed the structural analysis of the sucrose binding pocket of AtSWEET11 and AtSWEET12 using molecular docking followed by rigorous molecular dynamics (MD) simulations. We observed that the sucrose molecule binds inside the central cavity and in the middle of the transmembrane (TM) region of AtSWEET11 and AtSWEET12, that allows the alternate access to the sucrose molecule from either side of the membrane during transport. Both AtSWEET11 and AtSWEET12, shares the similar amino acid residues that interact with sucrose molecule. Further, to achieve more insights on the role of these two transporters in other plant species, we did the phylogenetic and the in-silico analyses of AtSWEET11 and AtSWEET12 orthologs from 39 economically important plants. We reported the extensive information on the gene structure, protein domain and cis-acting regulatory elements of AtSWEET11 and AtSWEET12 orthologs from different plants. The cis-elements analysis indicates the involvement of AtSWEET11 and AtSWEET12 orthologs in plant development and also during abiotic and biotic stresses. Both in silico and in planta expression analysis indicated AtSWEET11 and AtSWEET12 are well-expressed in the Arabidopsis leaf tissues. However, the orthologs of AtSWEET11 and AtSWEET12 showed the differential expression pattern with high or no transcript expression in the leaf tissues of different plants. Overall, these results offer the new insights into the functions and regulation of AtSWEET11 and AtSWEET12 orthologs from different plant species. This might be helpful in conducting the future studies to understand the role of these two crucial transporters in Arabidopsis and other crop plants.
AtSWEET11 and AtSWEET12: the twin traders of sucrose
(Elsevier B.V., 2022) Fatima, Urooj; Anjali, Anjali; Senthil-Kumar, Muthappa
AtSWEET11 and AtSWEET12 are central players in phloem loading and long-distance sucrose translocation. During drought stress, these transporters enhance sucrose transport from shoot to root, increasing root proliferation. Chen et al. have now unravelled novel aspects of sucrose transport regulation, occurring via AtSWEET11 and AtSWEET12 phosphorylation and oligomerisation.
Biological mechanisms of plant interactions with a combination of biotic and abiotic stresses
(Frontiers Media S.A., 2019) Morel, Jean-benoit; Senthil-Kumar, Muthappa; Ballini, Elsa
This Research Topic addresses the way plants respond to a combination of different types of stresses, for instance, how a plant deals with simultaneous attacks by pathogens (biotic stress) and environmental stresses (abiotic stress). While most plant research has been focused on the understanding of individual biotic or abiotic stress responses, we propose to encourage submissions on a broader approach that better represents stress conditions encountered in the field. Indeed, in nature or under field conditions plants are not just dealing with one environmental stress: they are often coping with several simultaneously occurring biotic and abiotic stresses. Recent findings indicate that predicting the plant response to a combination of stresses cannot be made from the knowledge of an individual stress, and therefore remains a major challenge. It remains to be determined what biological systems respond to combined stresses. Hormones, with their complex regulation and cross-talk, as well as molecules like calcium or reactive oxygen species, are likely to play a key role in combined stresses as potential integrators of multiple signaling pathways. Moreover, given the importance of epigenetic changes in response to a given stress, the role of epigenetic modifications during combined stresses needs further attention. Combined stresses may not only be concomitant but be successive, either during a plant’s life or across generations. In that respect, trans-generational, epigenetic changes and more generally stress memory mechanisms could also be important for our understanding of combinational stresses. Interestingly, dual RNA-Seq and other approaches also indicate that besides the measured changes in plants, pathogen transcriptional programs are also severely and indirectly affected by stresses applied to their host plants. This Research Topic welcomes the submission of all article types, with a preference for Original Research, Reviews, and Opinions, focusing on the following: (1) analysis at the molecular and physiological level of combined stresses, and if possible also describing the behavior of the pathogen, (2) genetic and epigenetic studies of combined biotic and abiotic stresses, (3) studies describing at the plant level or within how a well-known mechanism involved in one type of stress is affected by another type of stress (e.g., how Resistance gene function is altered by heat), (4) studies using bioinformatics/computational tools to analyze various publicly available transcriptomic/proteomic/metabolomic datasets, provided that the genomic studies have adequate biological/functional validation, All types of common pathogens (viruses, bacteria, fungi, nematodes) and insects are welcome, which exclude probiotic or beneficial organisms; abiotic stresses may also include agronomical constraints, like nutrient fertilization. In this Research Topic, ‘combined stress’ is understood as a combination of one biotic stress with at least one abiotic stress. Studies need to provide a mechanisms or a molecular level understanding of stress interaction, and not just an evaluation. Manuscripts dealing with each type of stress separately (e.g., “gene X confers both drought tolerance and pathogen resistance”) will not be considered.
A blotting paper technique for the screening of chickpea genotypes against dry root rot disease
(Springer Nature Publishing AG, 2026) Durgadevi, Athimoolam; Pandey, Prachi; Senthil-Kumar, Muthappa
Dry root rot (DRR) disease is a major threat to chickpea production across the world. This disease is caused by a soil-borne necrotrophic fungal pathogen, Macrophomina phaseolina. The use of disease-resistant varieties paves the way to conquer the disease spread. Though chickpea germplasm with rich genetic diversity is available around the world, its response to DRR is still unexplored. In turn, this demands screening and identification of resistant genotypes for crop protection against the disease. Here we describe an improved blotting paper technique for the large-scale screening of chickpea genotypes for DRR resistance. The method is quick, cost-effective, less labour-intensive, and thus optimized for high-throughput screening and can be efficiently used to screen a large number of chickpea genotypes for resistance against DRR.
Callus induction and efficient in vitro plant regeneration protocol for Chickpea
(Springer Nature Publishing AG, 2024) Jangid, Vinod Kumar; Senthil-Kumar, Muthappa; Chandran, Divya; Sinharoy, Senjuti
The development of an efficient and consistent callus-mediated in vitro regeneration protocol is crucial for biotechnological approaches aimed at improving chickpea, an economically important crop legume. In this study, we assess the effectiveness of callus-mediated regeneration in different chickpea genotypes. Through in vitro screening of explants, we identified the Indian cultivar Pusa 240 as a favourable genotype with higher efficiency of somatic embryogenesis and in vitro plant regeneration. Building upon this finding, we have successfully established two distinct protocols for chickpea callus-mediated somatic embryogenesis, utilizing leaf and hypocotyl explants obtained from the Pusa 240 genotype. These protocols achieved plant regeneration efficiencies of 27% using leaf explants and 46.6 − 66% using hypocotyl explants. Extensive literature review and comparative analysis underscored the superiority of our current protocol. Subsequently, the regenerated plants were successfully acclimatized and transferred to the greenhouse, exhibiting normal phenotypic growth. This detailed regeneration method will provide a valuable resource for chickpea genetic transformations and the generation of large mutant populations where embryogenesis via callus formation is required. The protocol presented here establishes a powerful tool for studying the functional genomics of chickpea plants and lays the foundation for future advancements in this field.
Combined drought and heat stress influences the root water relation and determine the dry root rot disease development under field conditions: A study using contrasting chickpea genotypes
(Frontiers Media S.A., 2022) Chilakala, Aswin Reddy; Mali, Komal Vitthalrao; Irulappan, Vadivelmurugan; Patil, Basavanagouda S.; Pandey, Prachi; Rangappa, Krishnappa; Ramegowda, Venkategowda; Kumar, M. Nagaraj; Puli, Chandra Obul Reddy; Mohan-Raju, Basavaiah; Senthil-Kumar, Muthappa
Abiotic stressors such as drought and heat predispose chickpea plants to pathogens of key importance leading to significant crop loss under field conditions. In this study, we have investigated the influence of drought and high temperature on the incidence and severity of dry root rot disease (caused by Macrophomina phaseolina) in chickpea, under extensive on- and off-season field trials and greenhouse conditions. We explored the association between drought tolerance and dry root rot resistance in two chickpea genotypes, ICC 4958 and JG 62, with contrasting resistance to dry root rot. In addition, we extensively analyzed various patho-morphological and root architecture traits altered by combined stresses under field and greenhouse conditions in these genotypes. We further observed the role of edaphic factors in dry root rot incidence under field conditions. Altogether, our results suggest a strong negative correlation between the plant water relations and dry root rot severity in chickpeas, indicating an association between drought tolerance and dry root rot resistance. Additionally, the significant role of heat stress in altering the dynamics of dry root rot and the importance of combinatorial screening of chickpea germplasm for dry root rot resistance, drought, and heat stress have been revealed.
Comparative transcriptome profiling reveals differential defense responses among Alternaria brassicicola resistant Sinapis alba and susceptible Brassica rapa
(Frontiers Media S.A., 2024) Ahmed, Reshma; Dey, Kuntal Kumar; Senthil-Kumar, Muthappa; Modi, Mahendra Kumar; Sarmah, Bidyut Kumar; Bhorali, Priyadarshini
Alternaria blight is a devastating disease that causes significant crop losses in oilseed Brassicas every year. Adoption of conventional breeding to generate disease-resistant varieties has so far been unsuccessful due to the lack of suitable resistant source germplasms of cultivated Brassica spp. A thorough understanding of the molecular basis of resistance, as well as the identification of defense-related genes involved in resistance responses in closely related wild germplasms, would substantially aid in disease management. In the current study, a comparative transcriptome profiling was performed using Illumina based RNA-seq to detect differentially expressed genes (DEGs) specifically modulated in response to Alternaria brassicicola infection in resistant Sinapis alba, a close relative of Brassicas, and the highly susceptible Brassica rapa. The analysis revealed that, at 48 hpi (hours post inoculation), 3396 genes were upregulated and 23239 were downregulated, whereas at 72 hpi, 4023 genes were upregulated and 21116 were downregulated. Furthermore, a large number of defense response genes were detected to be specifically regulated as a result of Alternaria infection. The transcriptome data was validated using qPCR-based expression profiling for selected defense-related DEGs, that revealed significantly higher fold change in gene expression in S. alba when compared to B. rapa. Expression of most of the selected genes was elevated across all the time points under study with significantly higher expression towards the later time point of 72 hpi in the resistant germplasm. S. alba activates a stronger defense response reaction against the disease by deploying an array of genes and transcription factors involved in a wide range of biological processes such as pathogen recognition, signal transduction, cell wall modification, antioxidation, transcription regulation, etc. Overall, the study provides new insights on resistance of S. alba against A. brassicicola, which will aid in devising strategies for breeding resistant varieties of oilseed Brassica.
Complex molecular mechanisms determine fitness of plants to biotic and abiotic stresses
(Springer Nature Publishing AG, 2021) Prasad, Ashish; Senthil-Kumar, Muthappa; Prasad, Manoj
The mode of growth and development of plants does not allow them to change their habitat upon stress imposition. Through the course of evolution, plants have acquired complex molecular pathways to deal with abiotic and biotic factors to ensure their survival. The changing climatic conditions have led to unprecedented weather patterns resulting in increased crop losses. Similarly, the spread of pathogens in an era of increasing international trade has resulted in introduction and adaptation of these pathogens to new areas and cause frequent epidemics. There is an increasing need to understand the molecular mechanisms underlying stress responses in plants and envision ways to develop new crop varieties with improved features.
Comprehensive analysis of small RNA-seq data reveals that combination of miRNA with its isomiRs increase the accuracy of target prediction in Arabidopsis thaliana
(Taylor & Francis Group, 2014) Ahmed, Firoz; Senthil-Kumar, Muthappa; Lee, Seonghee; Dai, Xinbin; Mysore, Kirankumar S; Zhao, Patrick Xuechun
Along with the canonical miRNA, distinct miRNA-like sequences called sibling miRNAs (sib-miRs) are generated from the same pre-miRNA. Among them, isomeric sequences featuring slight variations at the terminals, relative to the canonical miRNA, constitute a pool of isomeric sibling miRNAs (isomiRs). Despite the high prevalence of isomiRs in eukaryotes, their features and relevance remain elusive. In this study, we performed a comprehensive analysis of mature precursor miRNA (pre-miRNA) sequences from Arabidopsis to understand their features and regulatory targets. The influence of isomiR terminal heterogeneity in target binding was examined comprehensively. Our comprehensive analyses suggested a novel computational strategy that utilizes miRNA and its isomiRs to enhance the accuracy of their regulatory target prediction in Arabidopsis. A few targets are shared by several members of isomiRs; however, this phenomenon was not typical. Gene Ontology (GO) enrichment analysis showed that commonly targeted mRNAs were enriched for certain GO terms. Moreover, comparison of these commonly targeted genes with validated targets from published data demonstrated that the validated targets are bound by most isomiRs and not only the canonical miRNA. Furthermore, the biological role of isomiRs in target cleavage was supported by degradome data. Incorporating this finding, we predicted potential target genes of several miRNAs and confirmed them by experimental assays. This study proposes a novel strategy to improve the accuracy of predicting miRNA targets through combined use of miRNA with its isomiRs.
Concurrent drought stress and vascular pathogen infection induce common and distinct transcriptomic responses in chickpea
(Frontiers Media S.A., 2017) Sinha, Ranjita; Gupta, Aarti; Senthil-Kumar, Muthappa
Chickpea (Cicer arietinum); the second largest legume grown worldwide is prone to drought and various pathogen infections. These drought and pathogen stresses often occur concurrently in the field conditions. However, the molecular events in response to that are largely unknown. The present study examines the transcriptome dynamics in chickpea plants exposed to a combination of water-deficit stress and Ralstonia solanacearum infection. R. solanacearum is a potential wilt disease causing pathogen in chickpea. Drought stressed chickpea plants were infected with this pathogen and the plants were allowed to experience progressive drought with 2 and 4 days of R. solanacearum infection called short duration stress (SD stresses) and long duration stress (LD stresses), respectively. Our study showed that R. solanacearum multiplication decreased under SD-combined stress compared to SD-pathogen but there was no significant change in LD-combined stress compared to LD-pathogen. The microarray analysis during these conditions showed that 821 and 1039 differentially expressed genes (DEGs) were unique to SD- and LD-combined stresses, respectively, when compared with individual stress conditions. Three and fifteen genes were common among all the SD-stress treatments and LD-stress treatments, respectively. Genes involved in secondary cell wall biosynthesis, alkaloid biosynthesis, defense related proteins, and osmo-protectants were up-regulated during combined stress. The expression of genes involved in lignin and cellulose biosynthesis were specifically up-regulated in SD-combined, LD-combined, and LD-pathogen stress. A close transcriptomic association of LD-pathogen stress with SD-combined stress was observed in this study which indicates that R. solanacearum infection also exerts drought stress along with pathogen stress thus mimics combined stress effect. Furthermore the expression profiling of candidate genes using real-time quantitative PCR validated the microarray data. The study showed that down-regulation of defense-related genes during LD-combined stress resulted in an increased bacterial multiplication as compared to SD-combined stress. Overall, our study highlights a sub-set of DEGs uniquely expressed in response to combined stress, which serve as potential candidates for further functional characterization to delineate the molecular response of the plant to concurrent drought-pathogen stress.
Concurrent stresses are perceived as new state of stress by the plants: overview of impact of abiotic and biotic stress combinations
(Springer, 2017) Gupta, Aarti; Senthil-Kumar, Muthappa
Crop plants under natural conditions often encounter abiotic and biotic stresses either individually or in combination, single or multiple times in their life cycle. During their concurrence, different stressors interact with each other over the plant interface leading to altered plant responses. Initial stressor can modulate plant physiology and thereby influences plant response towards another stressor. Consequent to the stress interaction, plants encountering concurrent stress show different responses in comparison to the plants exposed to the individual stresses. Additionally, plant defence responses are somewhat skewed towards one stressor during concurrent occurrence of stresses. Such different responses are the cognate ‘net effect’ of combined stress felt by the plant. The net effect exhibited by plants under combined stress is unique to each stress combination. Thus, in lieu of the combined stress responses, which are different from the individual stress responses, the combined stress has been proposed as a new state of stress. Plant responses towards this new state are not just dictated by either of the individual stresses alone but by more complex interaction. In this chapter, we present an overview of the combined stresses with emphasis on drought and bacterial stressors and discuss the stress interaction effect and net effect.
Cross-talk signaling in rice during combined drought and bacterial blight stress
(Frontiers Media S.A., 2019) Vemanna, Ramu S; Bakade, Rahul; Bharti, Pooja; Kumar, MK Prasanna; Sreeman, Sheshshayee M; Senthil-Kumar, Muthappa; Makarla, Udayakumar
Due to climatic changes, rice crop is affected by moisture deficit stress and pathogens. Tissue water limitation besides reducing growth rates, also renders the crop susceptible to the infection by Xanthomonas oryzae pv. oryzae (Xoo) that causes bacterial leaf blight. Independently, both drought adaptation and Xoo resistance have been extensively studied. Though the cross-talk between drought and Xoo stress responses have been explored from individual stress studies, examining the combinatorial stress response is limited in rice. Recently published combined stress studies showed that under the combined stress, maintenance of carbon assimilation is hindered and such response is regulated by overlapping cellular mechanisms that are different from either of the individual stresses. Several receptors, MAP kinases, transcription factors, and ribosomal proteins, are predicted for playing a role in cellular homeostasis and protects cells from combined stress effects. Here we provide a critical analysis of these aspects using information from the recently published combined stress literature. This review is useful for researchers to comprehend combinatorial stress response of rice plants to drought and Xoo.
Current understanding of regulation of GBF3 under abiotic and biotic stresses and its potential role in combined stress tolerance
(Taylor & Francis Group, 2019) Dixit, Sandeep Kumar; Gupta, Aarti; Senthil-Kumar, Muthappa
G-box binding factors (GBFs) belong to basic leucine zipper (bZIP) super family of transcription factors. Among six reported members of Arabidopsis thaliana GBFs, AtGBF3 transcripts has been shown to accumulate to high levels in dry seed, stamens, mature pollen and siliques. Amino acid sequence analysis of AtGBF3 reveals presence of proline rich region at N-terminus and basic leucine zipper domain at C-terminus. Earlier, it has been demonstrated that GBFs bind to the G-box element found within the promoter of stress responsive genes including alcohol dehydrogenase (AtAdh) and activate its transcription. Expression profile of AtGBF3 depicts increase in mRNA levels in plants under drought, osmotic, heat, salt and cold stress and biotic stresses. In silico analysis reveals GBF3 localization in nucleus and cytoplasm. Cues from localization studies on GBF3 homologs suggest that upon stress signal perception, GBF3 is phosphorylated and localized to nucleus where it can regulate expression of stress related genes. Till now target genes of GBF3 and mechanism of their regulation during individual and combined abiotic - biotic stresses is not comprehensively reviewed. Through our analysis in this review, we propose GBF3 as major player in integrating abscisic acid and salicylic acid cross talk during combined stress.
Drought attenuates plant defence against bacterial pathogens by suppressing the expression of CBP60g/SARD1 during combined stress
(John Wiley & Sons, 2022) Choudhary, Aanchal; Senthil-Kumar, Muthappa
In nature, plants are frequently exposed to drought and bacterial pathogens simultaneously. However, information on how the drought and defence pathways interact and orchestrate global transcriptional regulation is limited. Here, we show that moderate drought stress enhances the susceptibility of Arabidopsis thaliana to Pseudomonas syringae pv. tomato DC3000. Using transcriptome meta-analysis, we found that drought and bacterial stress antagonistically modulate a large set of genes predominantly involved in salicylic acid (SA) and abscisic acid (ABA) signalling networks. We identified that the levels of SA and ABA are dynamically regulated during the course of stress. Importantly, under combined stress, drought through the ABA pathway downregulates the induction of CALMODULIN-BINDING PROTEIN 60g (CBP60g) and SYSTEMIC ACQUIRED RESISTANCE DEFICIENT 1 (SARD1), two transcription factors crucial for SA production upon bacterial infection. We also identified an important role of NPR1-LIKE PROTEIN 3 and 4 (NPR3/4) transcriptional repressors in the drought-mediated negative regulation of CBP60g/SARD1 expression. Using a genetic approach, we show that CBP60g/SARD1 expression is the key determinant of plant defence against bacterial pathogens under combined stress. Thus, these transcription factors act as critical nodes for the crosstalk between drought and bacterial stress signalling under combined stress in plants.
Drought attenuates plant responses to multiple rhizospheric pathogens: A study on a dry root rot-associated disease complex in chickpea fields
(Elsevier B.V., 2023) Chilakala, Aswin Reddy; Pandey, Prachi; Durgadevi, Athimoolam; Kandpal, Manu; Patil, Basavanagouda S.; Rangappa, Krishnappa; Reddy, Puli Chandra Obul; Ramegowda, Venkategowda; Senthil-Kumar, Muthappa
Context or problem: Root rots, a major factor contributing to yield loss in chickpea, often occur in disease complexes. Objective or research question: Plant responses to disease complexes are not well elucidated. We sought a clear understanding of a newly identified disease complex in chickpea, dry root rot (DRR)–wilt disease complex, in the field and studied the effect of drought on the severity of the complex and its effect on yield. We compared plant responses to DRR alone and the disease complex under drought and determined the phytohormones involved in plant defense against the disease complex. Methods: We compared the effect of 14 environments (two soil moisture regimes at seven locations) on the incidence of the disease complex and yield loss in four chickpea genotypes. We also studied the effect of drought on rhizospheric and root endo-microbial communities by whole-genome and metagenomic sequencing and performed LC-MS-based phytohormonal profiling of chickpea roots. Results: Soil moisture and plant genetic variability were critical in modulating disease incidence in field conditions. DRR was the primary driver of the disease complex under drought stress. Drought aggravated the yield reductions caused by the disease complex from 35% to 60% in susceptible genotypes. Further, drought-tolerant genotypes performed better under combined disease complex infection and drought stress and exhibited lesser yield losses than susceptible genotypes. Pathogenic fungi such as Macrophomina phaseolina, Fusarium oxysporum, and Rhizoctonia solani were enriched in the chickpea rhizosphere, and M. phaseolina was predominant in infected chickpea roots under both well-watered and drought conditions. Symbiotic associations of chickpea with nitrogen-fixing bacteria were suppressed under drought stress. Abscisic acid, jasmonic acid, and salicylic acid were found to be involved in defense against the disease complex across various stages of plant growth. Implications or significance: We highlight the interaction between drought and soil pathogens affecting chickpea yield and suggest the utilization of drought-tolerant root traits as donor traits for improving combined stress resistance. We also demonstrate growth stage–dependent phytohormonal responses elicited by DRR and the DRR–wilt disease complex. The identification and management of root rots is essential, and our findings offer valuable new insights into a lesser-known but highly significant disease complex of chickpea. Data availability statement: Manuscript data is available at Supplementary File S1. The soil microbe whole-genome and metagenome and root-microbe 16 S and ITS sequencing data are available at NCBI PRJNA871091 and PRJNA895851.