Search

Combined abiotic and biotic stresses modify plant defense signaling, leading to either the activation or suppression of defense responses. Although the majority of combined abiotic and biotic stresses reduce plant fitness, certain abiotic stresses reduce the severity of pathogen infection in plants. Remarkably, certain pathogens also improve the tolerance of some plants to a few abiotic stresses. While considerable research focuses on the detrimental impact of combined stresses on plants, the upside of combined stress remains hidden. This review succinctly discusses the interactions between abiotic stresses and pathogen infection that benefit plant fitness. Various factors that govern the positive influence of combined abiotic stress and pathogen infection on plant performance are also discussed. In addition, we provide a brief overview of the role of pathogens, mainly viruses, in improving plant responses to abiotic stresses. We further highlight the critical nodes in defense signaling that guide plant responses during abiotic stress towards enhanced resistance to pathogens. Studies on antagonistic interactions between abiotic and biotic stressors can uncover candidates in host plant defense that may shield plants from combined stresses. [ABSTRACT FROM AUTHOR]

SUMMARY: The membrane‐bound heterotrimeric G‐proteins in plants play a crucial role in defending against a broad range of pathogens. This study emphasizes the significance of Extra‐large Gα protein 2 (XLG2), a plant‐specific G‐protein, in mediating the plant response to Sclerotinia sclerotiorum, which infects over 600 plant species worldwide. Our analysis of Arabidopsis G‐protein mutants showed that loss of XLG2 function increased susceptibility to S. sclerotiorum, accompanied by compromised accumulation of jasmonic acid (JA) during pathogen infection. Overexpression of the XLG2 gene in xlg2 mutant plants resulted in higher resistance and increased JA accumulation during S. sclerotiorum infection. Co‐immunoprecipitation (co‐IP) analysis on S. sclerotiorum infected Col‐0 samples, using two different approaches, identified 201 XLG2‐interacting proteins. The identified JA‐biosynthetic and JA‐responsive proteins had compromised transcript expression in the xlg2 mutant during pathogen infection. XLG2 was found to interact physically with a JA‐responsive protein, Coronatine induced 1 (CORI3) in Co‐IP, and confirmed using split firefly luciferase complementation and bimolecular fluorescent complementation assays. Additionally, genetic analysis revealed an additive effect of XLG2 and CORI3 on resistance against S. sclerotiorum, JA accumulation, and expression of the defense marker genes. Overall, our study reveals two independent pathways involving XLG2 and CORI3 in contributing resistance against S. sclerotiorum. Significance Statement: XLG2 and CORI3 proteins interact to confer defense against Sclerotinia sclerotiorum, primarily through the JA pathway, while also suggesting the involvement of independent defense mechanisms. [ABSTRACT FROM AUTHOR]

Plants deposit lignin in the secondary cell wall as a common response to drought and pathogen attacks. Cell wall localised multicopper oxidase family enzymes LACCASES (LACs) catalyse the formation of monolignol radicals and facilitate lignin formation. We show an upregulation of the expression of several LAC genes and a downregulation of microRNA397 (CamiR397) in response to natural drought in chickpea roots. CamiR397 was found to target LAC4 and LAC17L out of twenty annotated LACs in chickpea. CamiR397 and its target genes are expressed in the root. Overexpression of CamiR397 reduced expression of LAC4 and LAC17L and lignin deposition in chickpea root xylem causing reduction in xylem wall thickness. Downregulation of CamiR397 activity by expressing a short tandem target mimic (STTM397) construct increased root lignin deposition in chickpea. CamiR397‐overexpressing and STTM397 chickpea lines showed sensitivity and tolerance, respectively, towards natural drought. Infection with a fungal pathogen Macrophomina phaseolina, responsible for dry root rot (DRR) disease in chickpea, induced local lignin deposition and LAC gene expression. CamiR397‐overexpressing and STTM397 chickpea lines showed more sensitivity and tolerance, respectively, to DRR. Our results demonstrated the regulatory role of CamiR397 in root lignification during drought and DRR in an agriculturally important crop chickpea. [ABSTRACT FROM AUTHOR]

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 60 g (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. Summary statement: Moderate drought attenuates plant defence responses against bacterial pathogens by suppressing the expression of CBP60g and SARD1, which encode two crucial transcription factors involved in activating salicylic acid machinery. [ABSTRACT FROM AUTHOR]

Understanding the intricate dynamic impact of combined stresses on plant growth and productivity amidst escalating climate change is one of the most prevalent challenges for today's plant stress biologists. This commentary emphasizes the necessity of employing a centralized resource to collect and analyse scattered data on combined and individual abiotic and biotic stresses in plants. Introducing the Stress Combinations and their Interactions in Plants Database, we underscore its role in consolidating and comprehending diverse omics datasets and facilitating interdisciplinary research efforts to advance agricultural research. [ABSTRACT FROM AUTHOR]

With the increasing understanding of fundamentals of gene silencing pathways in plants, various tools and techniques for downregulating the expression of a target gene have been developed across multiple plant species. This chapter provides an insight into the molecular mechanisms of gene silencing and highlights the advancements in various gene silencing approaches. The prominent aspects of different gene silencing methods, their advantages and disadvantages have been discussed. A succinct discussion on the newly emerged microRNA-based technologies like microRNA-induced gene silencing (MIGS) and microRNA-mediated virus-induced gene silencing (MIR-VIGS) are also presented. We have also discussed the gene-editing system like CRISPR-Cas. The prominent bottlenecks in gene silencing methods are the off-target effects and lack of universal applicability. However, the tremendous growth in understanding of this field reflects the potentials for improvements in the currently available approaches and the development of new widely applicable methods for easy, fast, and efficient functional characterization of plant genes., (© 2022. Springer Science+Business Media, LLC, part of Springer Nature.)

The high throughputness and affordability of "omics" technologies is leading to the identification of a large number of abiotic stress genes, with many of them responsive to multiple stresses. In vivo functional characterization of these genes under multiple stresses is challenging but essential to develop resilient crops for the changing climate. Here we describe a high-throughput Virus-Induced Gene Silencing-based methodology for functional analysis of genes under multiple abiotic stresses using leaf disks. Leaves with maximal silencing, which is localized to only a few leaves and to a short period, can be effectively used for multiple stress imposition and stress affect quantification., (© 2022. Springer Science+Business Media, LLC, part of Springer Nature.)