Publications of NIPGR Scientists

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Author: search.filters.author.Choudhary, Aanchal

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    Drought: A context-dependent damper and aggravator of plant diseases
    (John Wiley & Sons, 2024) Choudhary, Aanchal; Senthil-Kumar, Muthappa
    Drought dynamically influences the interactions between plants and pathogens, thereby affecting disease outbreaks. Understanding the intricate mechanistic aspects of the multiscale interactions among plants, pathogens, and the environment—known as the disease triangle—is paramount for enhancing the climate resilience of crop plants. In this review, we systematically compile and comprehensively analyse current knowledge on the influence of drought on the severity of plant diseases. We emphasise that studying these stresses in isolation is not sufficient to predict how plants respond to combined stress from both drought and pathogens. The impact of drought and pathogens on plants is complex and multifaceted, encompassing the activation of antagonistic signalling cascades in response to stress factors. The nature, intensity, and temporality of drought and pathogen stress occurrence significantly influence the outcome of diseases. We delineate the drought-sensitive nodes of plant immunity and highlight the emerging points of crosstalk between drought and defence signalling under combined stress. The limited mechanistic understanding of these interactions is acknowledged as a key research gap in this area. The information synthesised herein will be crucial for crafting strategies for the accurate prediction and mitigation of future crop disease risks, particularly in the context of a changing climate.
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    The war for apoplastic water: stomatal control as a key strategy in bacterial pathogenesis
    (Springer Nature Publishing AG, 2023) Choudhary, Aanchal; Senthil-Kumar, Muthappa
    In this commentary, important recent discoveries on effector-mediated manipulation of apoplast hydration and the involvement of ABA machinery that are targeted in later stages of bacterial infection culminating in stomatal closure are highlighted. This article also sheds light on the differences in early and later stages of infection wherein the COR signaling in the initial phase promotes stomatal opening while in later stages ABA signaling overrides and forces the stomata to close. Also, the current understanding of pathogen-driven modulation of leaf water status during infection, in which stomata act as a crucial battleground between pathogens and plants at the post-invasive stage is summarized.
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    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.
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    Investigation of the novel transcriptional changes under combined drought and bacterial stress underpins the role of AtMYB96 in imparting tolerance
    (Springer Nature Publishing AG, 2021) Choudhary, Aanchal; Senthil-Kumar, Muthappa
    The physiological and molecular responses instigated to combat drought and bacterial pathogens often work antagonistically and, in most cases, the impact of combined stress is more detrimental to plant growth. Interestingly, plants exposed to this stress combination show a novel transcriptome fingerprint with a significant set of genes that are uniquely altered under combined stress. Despite this being reported in several transcriptomic datasets, our molecular understanding of these combined stress-specific genes and pathways is still in its nascent stages. These unique genes and the dedicated regulatory pathways are important for understanding the molecular aspects of signaling responses under combined stress. In this study, a previously available microarray dataset was extensively reanalysed to identify the novel genes and pathways specifically altered under combined stress. Using a combination of bioinformatic and data-guided approaches, we identified major biological pathways, transcription factor (TF) network and novel motifs potentially involved in the combined stress-specific responses. The candidate gene analysis using gene expression and mutant analysis identified AtMYB96 as an important TF involved in combined stress response. Taken together, our analysis pinpoints many novel genes that can be used for understanding the molecular mechanism of how plants deal with the combination of drought and bacterial pathogen.
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    An efficient, high-throughput method for the simultaneous exposure of drought stress and bacterial infection in plants
    (John Wiley & Sons, 2020) Choudhary, Aanchal; Senthil-Kumar, Muthappa
    PREMISE: We developed a systematic protocol for the easy, high-throughput, qualitative, and quantitative assessment of the patho-morphological, physiological, and molecular responses of Arabidopsis thaliana plants simultaneously subjected to drought and bacterial infection. This approach will assist studies elucidating plant adaptation strategies to combat combined stresses. METHODS AND RESULTS: Plants were grown in small screw-capped containers, individual pots, or pot strips. Watering was withheld from 30-day-old plants, which were subsequently infected with Pseudomonas syringae pv. tomato DC3000 using a dip inoculation. The natural development of both drought and bacterial infection was successfully and rapidly replicated in large numbers of plants, which is difficult to achieve with existing protocols. CONCLUSIONS: Our protocol offers a simple, low-cost, high-throughput strategy for the rapid and easy bacterial infection of large numbers of plants. It can be used in large-scale mutant and ecotype screenings under combined stresses and for other foliar pathogens in different plant species.
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    Transcriptomic changes under combined drought and nonhost bacteria reveal novel and robust defenses in Arabidopsis thaliana
    (Elsevier B.V., 2017) Choudhary, Aanchal; Gupta, Aarti; Ramegowda, Venkategowda; Senthil-Kumar, Muthappa
    Plants in the natural conditions are often challenged by a combination of two or more stressors. A combination of drought and pathogen is one of the most pressing threats to the plant’s growth and survival in the field, and thus warrants a mechanistic understanding. Susceptible plant-pathogen interaction, owing to effector-mediated suppression of plant defense responses, limits its scope for combined stress studies. In the present study, we have investigated the morpho-physiological responses of Arabidopsis thaliana to simultaneous drought and nonhost bacterial pathogen Pseudomonas syringae pv. tabaci. Combined stress treatment provoked an early and more pronounced hypersensitive response in the plant as compared to the non-host pathogen treatment. We have further deciphered the molecular basis for the robust defense response observed under combined stress by transcriptomic profiling carried out using whole-genome microarray. We found that the enhanced resistance to the combined stress is accompanied by a massive transcriptional reprogramming involving several transcripts specifically responding to the stress combination. A prominent over-representation of genes involved in basal defense-related machinery was observed under the combined stress. Genes involved in various defense signaling cascades, accumulation of secondary metabolites and those encoding for receptor-like kinases were highly up-regulated under the combined stress. Up-regulated genes related to redox homeostasis and hypersensitive response (HR)-mediated cell death were also found to be markedly enriched under combined stress. We also compared the global gene expression profile of A. thaliana subjected to combined drought-nonhost bacteria to those treated with a combination of drought-host bacteria Pseudomonas syringae pv. tomato DC3000. A significant induction of genes responding to drought as well as bacteria was observed during both the interactions. However, the amplitude of induction was more pronounced under the combination of drought and nonhost bacteria. Our results also indicate that plant activates multiple defense pathways upon exposure to combined stress which strengthens the overall basal immunity of the plant, characterized by a stronger HR response.
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    Tailored responses to simultaneous drought stress and pathogen infection in plants
    (Springer, 2016) Choudhary, Aanchal; Pandey, Prachi; Senthil-Kumar, Muthappa
    Under field conditions plants are often challenged by combination of biotic and abiotic stressors and they severely affect crop productivity. An increasing number of studies suggest that plants “tailor” their adaptation strategies to combat simultaneously occurring stresses. The stress combat strategies of plants are customized according to the stress combination and vary with the intensity and timing of the stresses involved. While some of the responses seen under combined stress are commonly instigated by individual stresses, some other are uniquely triggered under combined stress. Since some responses are unique only to the combined stress, the outcome of a stress interaction cannot be completely predicted using results from individual stress studies. In this chapter, the effects of combinatorial drought stress and pathogen infection on plants are discussed with an emphasis on the molecular and physiological mechanisms that underpin how plants tolerate simultaneously occurring stresses. We also highlight the complexity involved in the responses of plants to multiple stresses and underscore the importance of studying plant stressors in combination.