Effect of gamma-ray induced mutagenesis on the NBS-LRR domain of mycoplasma resistance proteins in sesame (Sesamum indicum L.)”

Abstract

Mycoplasma like organisms (MLO) is responsible for sesame phyllody which affects the seed yield and oil production. Mutant lines scanned with triggered innate immune system and proteomic insights aid to develop phyllody-resistant sesame genotypes. However, little information is known about the subtle changes in the sub-domains of R- gene in the mutant population. In this study, sesame genotype TMV7 was subjected to gamma radiation at different dosages, and the mutant population was selected based on their response to phyllody disease. The mutants were screened for key phenotypic traits such as seed and oil yield and percent disease incidence. Consequently, nine outstanding mutants were forwarded for subsequent generations (M₂) with a population size of 400 plants per mutant line. Mutants showing less disease incidence and higher seed/oil yield were used for molecular docking and abundance of R-gene transcripts. Out of nine mutant populations developed, Mut1 and Mut3 showed least disease incidence and higher oil yield. Molecular docking of nucleotide binding ARC domain of R-protein revealed a significant increase in the interaction of H bonding with ADP in Mut1 which is mediated by Gly- residue of the P-loop. The substituted Pro140 forms hydrophobic alkyl bonding which is responsible for the folding of protein. Post infection studies showed that the expression of R-gene has increased by 29.5 folds in the mutant lines as compared with the TMV7 (non-irradiated). The study showed that the innate immunity developed in the phyllody resistant lines is accompanied with the amino-acid substitution in the NB-ARC domain of R-protein. The lines identified with higher resistance and oil yield can be used to develop sesame phyllody resistant genotypes with improved yield.