In-silico identification and differential expressions of LepR4-syntenic disease resistance related domain containing genes against blackleg causal fungus Leptosphaeria maculans in Brassica oleracea

Blackleg, caused by Leptosphaeria maculans, is a devastating disease for which no resistant (R) gene is reported in cabbage (C-genome). All known R-genes for blackleg in Brassicaceae have been identified in A- or B-genome. However, identification of a few blackleg-resistant cabbage genotypes suggest that C-genome crops may also contain R-genes. Since, there is high ancestral synteny between these three genomes, we reasoned that mining the syntenic regions of known A- or B-genome R-genes may lead to the corresponding functional orthologues in C-genome. Here, we investigated the Brassica napus blackleg resistant-loci LepR4 and identified two syntenic blocks of 9.56 and 1 Mb in chromosomes C03 and C08, respectively, hosting a total of 1137 genes in C- genome. Among these, twelve genes have functional domains such NB-ARC, LRR, CC, TIR, MAP-kinase and S_TKc that have putatively roles in disease resistance. Higher expressions of leucine-rich repeat receptor-like kinase genes Bo3g110840 and Bo3g103150 against two L. maculans isolates in two resistant genotypes and of Serine/Threonine protein kinase genes Bo3g114980 and Bo3g130040 against both isolates in one resistant genotype and against one isolate in both resistant genotypes, respectively suggest their putative roles in conferring resistance to blackleg in cabbage. This approach is auxiliary to conventional mapping based approach and can be replicated for identifying all other A- or B-genome syntenic putative R-genes in C-genome which, upon validation by functional assays, will be helpful in enhancing our understanding and improving blackleg resistance in cabbage.