Relevance of methionine sulfoxide reductase(s) (MSR) as candidate proteins in redox homeostasis-mediated resistance response to Helicoverpa armigera (Hübner) in the pigeonpea wild relative Cajanus platycarpus (Benth.) Maesen.

Pod borer, Helicoverpa armigera, a polyphagus herbivore causes extensive economic losses to crops, including pigeonpea. Exploitation of pod borer resistance in wild relatives is pertinent due to the absence of resistance sources in cultivated pigeonpea and crossing-incompatibility with the resistant wild relatives. We present leads obtained in deeper understanding of pod borer resistance mechanism in Cajanus platycarpus, a pigeonpea wild relative. Surge in cellular ROS during herbivory leads to redox-PTMs (post translational modifications) of methionine-rich proteins including antioxidant enzymes, causing oxidative damage. Plants then officiate methionine sulfoxide reductases (MSRs), that maintain the redox status of methionine and hence homeostasis. We demonstrate functionality of MSRs (MSRA and MSRB) in the resistance response of the wild relative to pod borer. Among 5 MSRA and 3 MSRB genes, CpMSRA2 and CpMSRB1 were herbivore-responsive based on expression during herbivory. Clues about the stress-responsiveness were obtained upon analyses of cis-elements and co-expressing genes. Apparently, the wild relative followed a non-canonical mode of redox management, as divulged by antioxidant enzymes and the scavenging capacity. Differential lipid peroxidation as an early response provided evidences for an effective redox management in the wild relative. This is the first report signifying redox homeostasis in the resistance response towards herbivory.

Structural modelling and molecular dynamics of a multi-stress responsive WRKY TF-DNA complex towards elucidating its role in stress signalling mechanisms in chickpea.

Chickpea is a premier food legume crop with high nutritional quality and attains prime importance in the current era of 795 million people being undernourished worldwide. Chickpea production encounters setbacks due to various stresses and understanding the role of key transcription factors (TFs) involved in multiple stresses becomes inevitable. We have recently identified a multi-stress responsive WRKY TF in chickpea. The present study was conducted to predict the structure of WRKY TF to identify the DNA-interacting residues and decipher DNA-protein interactions. Comparative modelling approach produced 3D model of the WRKY TF with good stereochemistry, local/global quality and further revealed W19, R20, K21, and Y22 motifs within a vicinity of 5 Å to the DNA amongst R18, G23, Q24, K25, Y36, Y37, R38 and K47 and these positions were equivalent to the 2LEX WRKY domain of Arabidopsis. Molecular simulations analysis of reference protein -PDB ID 2LEX, along with Car-WRKY TF modelled structure with the DNA coordinates derived from PDB ID 2LEX and docked using HADDOCK were executed. Root Mean Square (RMS) Deviation and RMS Fluctuation values yielded consistently stable trajectories over 50 ns simulation. Strengthening the obtained results, neither radius of gyration, distance and total energy showed any signs of DNA-WRKY complex falling apart nor any significant dissociation event over 50 ns run. Therefore, the study provides first insights into the structural properties of multi-stress responsive WRKY TF-DNA complex in chickpea, enabling genome wide identification of TF binding sites and thereby deciphers their gene regulatory networks.