Genome-wide analysis of MLO genes reveals evolutionary characteristics and patterns favorable for understanding plant-pathogen interactions

Abstract Mildew Resistance Locus O (MLO) proteins play a crucial role in plant-pathogen interactions, especially with regard to susceptibility to powdery mildew (PM). In this study, structural characteristics of MLO genes and proteins in several plant species and phylogenetic relationships were investigated, highlighting evolutionary patterns and characteristics responsible for the function of these proteins. To this end, MLO genes associated with plant susceptibility to PM and their putative promoter regions (PPRs) were investigated in relation to their genomic characteristics and composition of cis-regulatory elements (CREs). From the amino acid sequences, various biochemical and cytological properties were studied, also obtaining a phylogenetic reconstruction. Both the topology of the segments (extracellular, transmembrane and cytoplasmic) of the MLO proteins and the identity matrices of these regions were analyzed. MLO proteins have a basic character, are rich in leucine, and present structural patterns such as functional domains, structural motifs, amino acid composition, and subcellular localization. As for the evolutionary highlights, the phylogenetic analysis revealed groupings consistent with the taxonomic classification of some families, such as Poaceae, Solanaceae and Brassicaceae. Analysis of identity matrices demonstrated that segments of the extracellular space are less conserved than those of the cytoplasmic space, with the transmembrane regions being the most conserved. The genes present a relatively conserved pattern in the size and distribution of introns/exons, and in relation to PPRs, specific patterns of CREs constitution were observed in the different clades, which implies the potential complexity of regulating the expression of these genes.