Genome-Wide Analysis and Differential Expression of Chitinases in Banana Against Root Lesion Nematode (Pratylenchus coffeae) and Eumusa Leaf Spot (Mycosphaerella eumusae) Pathogens

Knowledge on structure and conserved domain of Musa chitinase isoforms and their responses to various biotic stresses will give a lead to select the suitable chitinase isoform for developing biotic stress-resistant genotypes. Hence, in this study, chitinase sequences available in the Musa genome hub were analyzed for their gene structure, conserved domain, as well as intron and exon regions. To identify the Musa chitinase isoforms involved in Pratylenchus coffeae (root lesion nematode) and Mycosphaerella eumusae (eumusa leaf spot) resistant mechanisms, differential gene expression analysis was carried out in P. coffeae- and M. eumusae-challenged resistant and susceptible banana genotypes. This study revealed that more number of chitinase isoforms (CIs) were responses upon eumusa leaf spot stress than nematode stress. The nematode challenge studies revealed that class II chitinase (GSMUA_Achr9G16770_001) was significantly overexpressed with 6.75-fold (with high fragments per kilobase of exon per million fragments mapped (FPKM)) in resistant genotype (Karthobiumtham-ABB) than susceptible (Nendran-AAB) genotype, whereas when M. eumusae was challenge inoculated, two class III CIs (GSMUA_Achr9G25580_001 and GSMUA_Achr8G27880_001) were overexpressed in resistant genotype (Manoranjitham-AAA) than the susceptible genotype (Grand Naine-AAA). However, none of the CIs were found to be commonly overexpressed under both stress conditions. This study reiterated that the chitinase genes are responding differently to different biotic stresses in their respective resistant genotypes.