Browsing by Author "Singh, Jawahar"

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Functional characterization of genes involved in legume nodulation using hairy root cultures
(Springer Nature Publishing AG, 2020) Singh, Jawahar; Kumar, Kamal; Verma, Praveen K.
Legumes, the second most important crop to humans possess unique ability to fix atmospheric nitrogen, making them one of the major contributors to sustainable agriculture. In legumes, molecular characterization of genes by stable transformation is difficult due to their recalcitrant nature to the whole-plant regeneration in desired varieties. The Agrobacterium rhizogenes-mediated generation of transgenic hairy roots or composite plants may facilitate a rapid and convenient alternative to study nodule biology. Functional analysis of genes involved in legume nodulation has been proven as successful for model legumes, viz., Medicago truncatula and Lotus japonicus, using transgenic hairy roots. Besides sharing some common features of nodulation among legumes, the symbiotic signaling is a complex and specific process. Here, we describe an improved protocol for hairy root transformation of a legume crop chickpea (Cicer arietinum L.) and the method to study nodulation to uncover the signaling components. Using the described protocol, transgenic hairy roots were generated in chickpea and selected based on the red fluorescence protein (RFP) microscopy. This protocol can be extended to other underutilized legumes.
Genome-wide identification, expression, and characterization of CaLysM-RLKs in chickpea root nodule symbiosis
(Elsevier B.V., 2022) Singh, Jawahar; Verma, Praveen K.
Legumes establish a nitrogen-fixing symbiosis with rhizobia which depends on the exchange of chemical signals between the two partners. Successful interaction between legumes and rhizobia depends on the perception of Nod factors (NFs) by the receptor-like kinases. A few cell surface receptors have been identified that perceive the rhizobial NFs and activate the downstream signaling pathway for nodulation in model legumes like Lotus japonicus and Medicago truncatula. However, crop legume such as chickpea lacks detailed analysis of LysM-RLKs genes for NFs perception. Here, we identified and characterized CaLysM-RLK genes and analyzed their gene structure, motif composition, chromosomal localization, phylogenetic relationship with Arabidopsis, Oryza sativa, and Medicago truncatula. To understand the spatiotemporal expression patterns, we performed transcript profiling of CaLysM-RLKs genes at a different time interval of the chickpea-rhizobia symbiotic interaction that revealed CaNFP and CaLYK3 can act as candidate genes for NF perception. Down-regulation of CaNFP and CaLYK3 in chickpea by agrobacterium rhizogenes mediated hairy root sysytem leads to signifificant reduction in nodule numbers. This study will be useful for improving root nodule symbiosis in chickpea.
NSP1 allies with GSK3 to inhibit nodule symbiosis
(Elsevier B.V., 2021) Singh, Jawahar; Verma, Praveen K.
Salt stress reduces N2 fixation by causing a reduction in nodule number, nodule weight, and nitrogenase activity in legumes. Emerging evidence from He et al. now suggests that glycogen synthase kinase 3 (GSK3) phosphorylates nodulation signaling pathway 1 (NSP1) in response to salt stress, reducing its DNA-binding activity, and thereby causing a reduction in nodulation.
Role of Nod factor receptors and its allies involved in nitrogen fixation
(Springer Nature Publishing AG, 2023) Singh, Jawahar; Verma, Praveen K.
The availability of water and nutrients in the soil is a major limiting factor affecting crop productivity. Plants of the Leguminosae family form a symbiotic association with nitrogen-fixing Gram-negative soil bacteria, rhizobia for nitrogen fixation. This symbiotic relationship between legumes and rhizobia depends on the signal exchange between them. Plant receptor-like kinases (RLKs) containing lysin motif (LysM) and/or leucine-rich repeat (LRR) play an important role in the perception of chemical signals from rhizobia for initiation and establishment of root nodule symbiosis (RNS) that results in nitrogen fixation. This review highlights the diverse aspects of LysM-RLK and LRR receptors including their specificity, functions, interacting partners, regulation, and associated signaling in RNS. The activation of LysM-RLKs and LRR-RLKs is important for ensuring the successful interaction between legume roots and rhizobia. The intracellular regions of the receptors enable additional layers of signaling that help in the transduction of signals intracellularly. Additionally, symbiosis receptor-like kinase (SYMRK) containing the LRR motif acts as a co-receptor with Nod factors receptors (LysM-RLK). Cleavage of the malectin-like domain from the SYMRK ectodomain is a mechanism for controlling SYMRK stability. Overall, this review has discussed different aspects of legume receptors that are critical to the perception of signals from rhizobia and their subsequent role in creating the mutualistic relationship necessary for nitrogen fixation. Additionally, it has been discussed how crucial it is to extrapolate the knowledge gained from model legumes to crop legumes such as chickpea and common bean to better understand the mechanism underlying nodule formation in crop legumes. Future directions have also been proposed in this regard.