Genome-wide identification and characterization of NBLRR genes in Finger millet (Eleusine coracana L.) and their expression in response to Magnaporthe grisea infection

Abstract

Background The nucleotide-binding site–leucine-rich repeat (NBLRR) genes significantly regulate defences against various phytopathogens. The genome-wide identification and analysis of NBLRR genes have been performed in several species. However, the evolution, structure, expression of NBLRRs and functional response to Magnaporthe grisea are not known in Finger millet (Eleusine coracana L.). Results The genome-wide scanning of the Finger millet genome resulted in 116 NBLRR genes named EcNBLRRsaccording to their chromosomal positions in ascending order. The phylogenetic analysis revealed divergence of NBLRRs as per the speciation of target species. The whole-genome duplications shaped the expansion of the NBLRR family in the finger millet genome, and purifying selection (Ka/Ks<1) shaped expansions of EcNBLRR paralog and ortholog pairs. The maximum orthology and syntenic association of NBLRRs was observed between Finger millet and Brachypodium distachyon over Finger millet and Arabidopsis thaliana. The promoter sequence analysis showed various stress- and phytohormone-responsive cis-acting elements besides growth and development, indicating their role in disease defence and regulatory mechanisms. The functional analysis of 22 EcNBLRRsin the genotypes showing contrasting responses to Magnaporthe grisea infection revealed the role of target EcNBLRRs in finger millet- Magnaporthe grisea interactions at early (EcNBLRR83; EcNBLRR55; EcNBLRR30 and EcNBLRR32) and late (EcNBLRR76; EcNBLRR45; EcNBLRR26; EcNBLRR23 and EcNBLRR21) stage of infections. Conclusion The identification and functional analysis of EcNBLRRs showed the role of EcNBLRR genes in assigning blast resistance in finger millet. These results pave the foundation for in-depth and targeted functional analysis of EcNBLRRs through genome editing and transgenic approaches.