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    Global bibliometry on three decades of methyl jasmonate-induced plant defense research reveals growth of a specialty area in biology
    (Open Science Publishers LLP, 2025) Chugh, Vipul; Kumari, Kamlesh; Yamal, Gupta; Checker, Vibha Gulyani; Yadav, Gitanjali; Kathpalia, Renu
    Methyl jasmonate (MeJA), a naturally existing plant hormone, acts as a vital defense and signaling molecule. Although this hormone has been discovered recently, published reports spanning the last several decades have shown the pleiotropic effects of the hormone raising numerous questions about its regulation, biogenesis, and mode of action. In this work, we explore the complete scientific research on MeJa from its discovery in 1992, spanning research conducted over three decades, through a complex network analysis of 2,542 documents authored by about 9,000 individuals. Several indicators of research progress were evaluated, including co-authorship networks, keyword thematic maps, indices of national and international collaboration, annual scientific production, and most productive affiliations. These indices not only enabled us to evaluate the importance of a specialty discipline in literature but also the place of nations in determining research directionality and the significance of quality of work. Overall, this bibliometric analysis identifies current research trends in a specialty area in biology and we hope that our work would pave the way for greater international collaborations among researchers and a better understanding of research gaps and future scope of work in the actively expanding field of MeJA induced plant defense, stress, and developmental processes.
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    XLG2 and CORI3 function additively to regulate plant defense against the necrotrophic pathogen Sclerotinia sclerotiorum
    (John Wiley & Sons, 2024) Tiwari, Ruchi; Garg, Kajal; Senthil-Kumar, Muthappa; Bisht, Naveen C.
    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.
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    When two negatives make a positive: The favorable impact of the combination of abiotic stress and pathogen infection on plants
    (Oxford University Press, 2024) Pandey, Prachi; Patil, Mahesh; Priya, Piyush; Senthil-Kumar, Muthappa
    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. Here, we discuss various factors that govern the positive influence of combined abiotic stress and pathogen infection on plant performance. We also 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.
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    A comprehensive investigation of lipid-transfer proteins from Cicer arietinum disentangles their role in plant defense against Helicoverpa armigera-infestation
    (Frontiers Media S.A., 2023) Saxena, Harshita; Negi, Harshita; Keshan, Radhika; Chitkara, Pragya; Kumar, Shailesh; Chakraborty, Amrita; Roy, Amit; Singh, Indrakant K.; Singh, Archana
    Lipid Transfer Proteins (LTPs) play a crucial role in synthesizing lipid barrier polymers and are involved in defense signaling during pest and pathogen attacks. Although LTPs are conserved with multifaceted roles in plants, these are not yet identified and characterized in Cicer arietinum. In this study, a genome-wide analysis of LTPs was executed and their physiochemical properties, biochemical function, gene structure analysis, chromosomal localization, promoter analysis, gene duplication, and evolutionary analysis were performed using in silico tools. Furthermore, tissue-specific expression analysis and gene expression analysis during pest attack was also conducted for the LTPs. A total of 48 LTPs were identified and named as CaLTPs. They were predicted to be small unstable proteins with "Glycolipid transfer protein" and "Alpha-Amylase Inhibitors, Lipid Transfer and Seed Storage" domains, that are translocated to the extracellular region. CaLTPs were predicted to possess 3-4 introns and were located on all the eight chromosomes of chickpea with half of the CaLTPs being localized on chromosomes 4, 5, and 6, and found to be closely related to LTPs of Arabidopsis thaliana and Medicago trancatula. Gene duplication and synteny analysis revealed that most of the CaLTPs have evolved due to tandem or segmental gene duplication and were subjected to purifying selection during evolution. The promoters of CaLTPs had development-related, phytohormone-responsive, and abiotic and biotic stress-related cis-acting elements. A few CaLTP transcripts exhibited differential expression in diverse tissue types, while others showed no/very low expression. Out of 20 jasmonate-regulated CaLTPs, 14 exhibited differential expression patterns during Helicoverpa armigera-infestation, indicating their role in plant defense response. This study identified and characterized CaLTPs from an important legume, C. arietinum, and indicated their involvement in plant defense against H. armigera-infestation, which can be further utilized to explore lipid signaling during plant-pest interaction and pest management.
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    PRpnp, a novel dual activity PNP family protein improves plant vigor and confers multiple stress tolerance in Citrus aurantifolia
    (John Wiley & Sons, 2023) Singh, Sweta; Chaudhary, Chanderkant; Bharsakale, Rushikesh D.; Gazal, Snehi; Verma, Lokesh; Tarannum, Zeba; Behere, G.T.; Giri, Jitender; Germain, Hugo; Ghosh, Dilip K; Sharma, Ashwani K; Chauhan, Harsh
    Under field conditions, plants are often simultaneously exposed to several abiotic and biotic stresses resulting in significant reductions in growth and yield; thus, developing a multi-stress tolerant variety is imperative. Previously, we reported the neofunctionalization of a novel PNP family protein, Putranjiva roxburghii purine nucleoside phosphorylase (PRpnp) to trypsin inhibitor to cater to the needs of plant defense. However, to date, no study has revealed the potential role and mechanism of either member of this protein group in plant defense. Here, we overexpressed PRpnp in Citrus aurantifolia which showed nuclear-cytoplasmic localization, where it functions in maintaining the intracellular purine reservoir. Overexpression of PRpnp significantly enhanced tolerance to salt, oxidative stress, alkaline pH, drought, and two pests, Papilio demoleus and Scirtothrips citri in transgenic plants. Global gene expression studies revealed that PRpnp overexpression up-regulated differentially expressed genes (DEGs) related to ABA- and JA- biosynthesis and signaling, plant defense, growth, and development. LC-MS/MS analysis validated higher endogenous ABA and JA accumulation in transgenic plants. Taken together, our results suggest that PRpnp functions by enhancing the endogenous ABA and JA, which interact synergistically and it also inhibits trypsin proteases in the insect gut. Also, like other purine salvage genes, PRpnp also regulates CK metabolism and increases the levels of CK-free bases in transgenic Mexican lime. We also suggest that PRpnp can be used as a potential candidate to develop new varieties with improved plant vigor and enhanced multiple stress resistance.
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    Feeding behaviour of generalist pests on Brassica juncea: implication for manipulation of glucosinolate biosynthesis pathway for enhanced resistance
    (John Wiley & Sons, 2017) Kumar, Pawan; Augustine, Rehna; Singh, Amarjeet Kumar; Bisht, Naveen C.
    Differential accumulation of plant defense metabolites has been suggested to have important ecological consequence in the context of plant-insect interactions. Feeding of generalist pests on Brassica juncea showed a distinct pattern with selective exclusion of leaf margins which are high in glucosinolates. Molecular basis of this differential accumulation of glucosinolates could be explained based on differential expression profile of BjuMYB28 homologs, the major biosynthetic regulators of aliphatic glucosinolates, as evident from quantitative real-time PCR and promoter:GUS fusion studies in allotetraploid B. juncea. Constitutive over-expression of selected BjuMYB28 homologs enhanced accumulation of aliphatic glucosinolates in B. juncea. Performance of two generalist pests, Helicoverpa armigera and Spodoptera litura larvae on transgenic B. juncea plants were poor compared to wild-type plants in a no-choice experiment. Correlation coefficient analysis suggested that weight gain of H. armigera larvae was negatively correlated with gluconapin (GNA) and glucobrassicanapin (GBN) whereas that of S. litura larvae was negatively correlated with GNA, GBN and sinigrin (SIN). Our study explains the significance and possible molecular basis of differential distribution of glucosinolates in B. juncea leaves and shows the potential of over-expressing BjuMYB28 for enhanced resistance of Brassica crops against the tested generalist pests.
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    Role of proline and pyrroline-5-carboxylate metabolism in plant defense against invading pathogens
    (Frontiers Media S.A., 2015) Qamar, Aarzoo; Mysore, Kirankumar S.; Senthil-Kumar, Muthappa
    Pyrroline-5-carboxylate (P5C) is an intermediate product of both proline biosynthesis and catabolism. Recent evidences indicate that proline-P5C metabolism is tightly regulated in plants, especially during pathogen infection and abiotic stress. However, role of P5C and its metabolism in plants has not yet been fully understood. Studies indicate that P5C synthesized in mitochondria has a role in both resistance (R)-gene-mediated and non-host resistance against invading pathogens. Proline dehydrogenase and delta-ornithine amino transferase-encoding genes, both involved in P5C synthesis in mitochondria are implicated in defense response of Nicotiana benthamiana and Arabidopsis thaliana against bacterial pathogens. Such defense response is proposed to involve salicylic acid-dependent pathway, reactive oxygen species (ROS) and hypersensitive response (HR)-associated cell death. Recently HR, a form of programmed cell death (PCD), has been proposed to be induced by changes in mitochondrial P5C synthesis or the increase in P5C levels per se in plants inoculated with either a host pathogen carrying suitable avirulent (Avr) gene or a non-host pathogen. Consistently, A. thaliana mutant plants deficient in P5C catabolism showed HR like cell death when grown in external P5C or proline supplemented medium. Similarly, yeast and plant cells under oxidative stress were shown to increase ROS production and PCD due to increase in P5C levels. Similar mechanism has also been reported as one of the triggers for apoptosis in mammalian cells. This review critically analyzes results from various studies and enumerates the pathways for regulation of P5C levels in the plant cell, especially in mitochondria, during pathogen infection. Further, mechanisms regulating P5C- mediated defense responses, namely HR are outlined. This review also provides new insights into the differential role of proline-P5C metabolism in plants exposed to pathogen infection.
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    Plant ribosomal proteins, RPL12 and RPL19, play a role in nonhost disease resistance against bacterial pathogens
    (Frontiers Media S.A., 2015) Nagaraj, Satish; Senthil-Kumar, Muthappa; Ramu, Vemanna S.; Wang, Keri; Mysore, Kirankumar S.
    Characterizing the molecular mechanism involved in nonhost disease resistance is important to understand the adaptations of plant-pathogen interactions. In this study, virus-induced gene silencing (VIGS)-based forward genetics screen was utilized to identify genes involved in nonhost resistance in Nicotiana benthamiana. Genes encoding ribosomal proteins, RPL12 and RPL19, were identified in the screening. These genes when silenced in N. benthamiana caused a delay in nonhost bacteria induced hypersensitive response (HR) with concurrent increase in nonhost bacterial multiplication. Arabidopsis mutants of AtRPL12 and AtRPL19 also compromised nonhost resistance. The studies on NbRPL12 and NbRPL19 double silenced plants suggested that both RPL12 and RPL19 act in the same pathway to confer nonhost resistance. Our work suggests a role for RPL12 and RPL19 in nonhost disease resistance in N. benthamiana and Arabidopsis. In addition, we show that these genes also play a minor role in basal resistance against virulent pathogens.
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    Channels hold the key: cyclic nucleotide gated channels (CNGC) in plant biotic stress signaling
    (International Society of Endocytobiology, 2015) Meena, Mukesh K.; Vadassery, Jyothilakshmi
    Cyclic nucleotide‐gated channels (CNGC) are non‐ selective cation channels opened by the direct binding of cyclic nucleotides and permit diffusion of divalent and monovalent cations, including Ca2+ and K+. The role of CNGC in various plant signaling process is emerging rapidly. Multiple studies have shown that CNGCs are involved in both basal and R gene mediated plant immunity. In this review, we will concentrate on the role of CNGCs in plant immunity, their role in calcium uptake in plants and on their relevance for plant phenotypic plasticity, focusing mostly on the well‐studied Arabidopsis CNGCs.
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    Regulation of primary plant metabolism during plant-pathogen interactions and its contribution to plant defense
    (Frontiers Media S.A., 2014) Rojas, Clemencia M.; Senthil-Kumar, Muthappa; Tzin, Vered; Mysore, Kirankumar S.
    Plants are constantly exposed to microorganisms in the environment and, as a result, have evolved intricate mechanisms to recognize and defend themselves against potential pathogens. One of these responses is the downregulation of photosynthesis and other processes associated with primary metabolism that are essential for plant growth. It has been suggested that the energy saved by downregulation of primary metabolism is diverted and used for defense responses. However, several studies have shown that upregulation of primary metabolism also occurs during plant-pathogen interactions. We propose that upregulation of primary metabolism modulates signal transduction cascades that lead to plant defense responses. In support of this thought, we here compile evidence from the literature to show that upon exposure to pathogens or elicitors, plants induce several genes associated with primary metabolic pathways, such as those involved in the synthesis or degradation of carbohydrates, amino acids and lipids. In addition, genetic studies have confirmed the involvement of these metabolic pathways in plant defense responses. This review provides a new perspective highlighting the relevance of primary metabolism in regulating plant defense against pathogens with the hope to stimulate further research in this area.