Genome sequence of Bipolaris maydis inciting maydis leaf blight provides insights into genome architecture and putative effector repertoire

Abstract

Maydis leaf blight (MLB) incited by Bipolaris maydis is one of the primary diseases of maize causing significant yield losses. For gaining a better insight into the genome organization and the molecular basis of pathogenesis related traits, the genome of B. maydis isolate BM_MG1 collected from maize fields in India, was sequenced using both the Illumina and Oxford Nanopore platforms. The final assembly yielded a genome size of 36.05 Mb with a GC content of 49.21 %. A total of 56 contigs were obtained with a N₅₀ of 2,100,550 bp. Gene prediction identified 9013 genes, with 8866 significantly annotated through BLASTX analysis using an E-value cutoff of 10⁻³. Amongst the transposable elements, the Gypsy elements were found to be highest in number. A total of 7534 simple sequence repeats were identified in the sequenced genome, with mononucleotide SSRs (3,434) being the most abundant type. Out of 510 secretory proteins identified, 136 were predicted as candidate secreted effector proteins (CSEPs), mainly including pectin lyase fold/virulence factors, alpha/beta hydrolase fold, and Concanavalin A-like lectin/glucanase domain superfamily proteins. The expression of glycoside hydrolase family 128 protein of B. maydis was found to be upregulated in the susceptible genotype of maize in our study, indicating its role in pathogenesis. The genomic and secretome information of B. maydis will provide valuable insights in understanding the intricate pathogenesis mechanisms and the arsenal of molecules deployed by the pathogen for effective colonization. In future, this information can be exploited for the development of improved management strategies.