Genome-wide characterization and comparative analysis of the MLO gene family in cotton

In plants, MLO (Mildew Locus O) gene encodes a plant-specific seven transmembrane (TM) domain protein involved in several cellular processes, including susceptibility to powdery mildew (PM). In this study, a genome-wide characterization of the MLO gene family in G. raimondii L., G. arboreum L. and G. hirsutum L. was performed. In total, 22, 17 and 38 homologous sequences were identified for each species, respectively. Gene organization, including chromosomal location, gene clustering and gene duplication, was investigated. Homologues related to PM susceptibility in upland cotton were inferred by phylogenetic relationships with functionally characterized MLO proteins. To conduct a comparative analysis between MLO candidate genes from G. raimondii L., G. arboreum L. and G. hirsutum L., orthologous relationships and conserved synteny blocks were constructed. The transcriptional variation of 38 GhMLO genes in response to exogenous application of salt, mannitol (Man), abscisic acid (ABA), ethylene (ETH), jasmonic acid (JA) and salicylic acid (SA) was monitored. Further studies should be conducted to elucidate the functions of MLO genes in PM susceptibility and phytohormone signalling pathways.