Genome-Wide Identification and Evolution of Receptor-Like Kinases (RLKs) and Receptor like Proteins (RLPs) in Brassica juncea

SIMPLE SUMMARY: Plants have evolved defence mechanisms to protect themselves against microbial pathogens. The identification of genes underlying quantitative trait loci is extremely challenging in complex polyploid genomes. In this research, we identify and characterise two types of resistance genes; RLKs (receptor like kinases) and RLPs (receptor like proteins) in Indian mustard (Brassica juncea), one of the major crops in India and an important member of the Brassicaceae family, which can be linked to QTL for disease resistance. The outcome provides a valuable resource for facilitating the identification of functional resistance genes which can be employed by breeders toward the production of resistant cultivars. ABSTRACT: Brassica juncea, an allotetraploid species, is an important germplasm resource for canola improvement, due to its many beneficial agronomic traits, such as heat and drought tolerance and blackleg resistance. Receptor-like kinase (RLK) and receptor-like protein (RLP) genes are two types of resistance gene analogues (RGA) that play important roles in plant innate immunity, stress response and various development processes. In this study, genome wide analysis of RLKs and RLPs is performed in B. juncea. In total, 493 RLKs (LysM-RLKs and LRR-RLKs) and 228 RLPs (LysM-RLPs and LRR-RLPs) are identified in the genome of B. juncea, using RGAugury. Only 13.54% RLKs and 11.79% RLPs are observed to be grouped within gene clusters. The majority of RLKs (90.17%) and RLPs (52.83%) are identified as duplicates, indicating that gene duplications significantly contribute to the expansion of RLK and RLP families. Comparative analysis between B. juncea and its progenitor species, B. rapa and B. nigra, indicate that 83.62% RLKs and 41.98% RLPs are conserved in B. juncea, and RLPs are likely to have a faster evolution than RLKs. This study provides a valuable resource for the identification and characterisation of candidate RLK and RLP genes.