Characterization of nine Mlo family genes and analysis of their expression against pathogen infections in Vitis flexuosa

Abstract

Mildew resistance locus o (Mlo) is a specific seven-transmembrane gene family that confers resistance against several abiotic and biotic stresses in plants. In this study, we identified nine Mlo-like loci,VfMlo-like3243 (Vitis flexuosa powdery-mildew resistance locus o-like3243), VfMlo-like4098, VfMlo-like5057, VfMlo-like6833, VfMlo-like7881, VfMlo-like8120, VfMlo-like14439, VfMlo-like14557, and VfMlo-like18484, which showed differential expression upon transcriptome analysis conducted using next generation sequencing (NGS) of V. flexuosa infected with Elsinoe ampelina. These genes are 1773–2548 bp long and encode deduced full-length proteins of 482–587 amino acids. The predicted amino acid sequences of all genes show typical Mlo domains containing seven highly conserved transmembrane domains, a calmodulin-binding domain and 30 important amino acid residues for Mlo function. While 3 VfMlo-like genes were downregulated, 5 VfMlo-like genes were up-regulated in grapevines infected with Erysiphe necator, among which four (VfMlo-like6833, VfMlo-like8120, VfMlo-like14439 and VfMlo-like18484) are orthologous to the AtMlo2, AtMlo6 and AtMlo12 genes involved in powdery mildew susceptibility. All genes except VfMlo-like17881 showed upregulated expression at 48 hpi after infection of Rhizobium vitis. The results revealed that the tested genes are related in responses to pathogens of grapevines and can be utilized as useful resources for investigating their roles in disease resistant responses in grapevines.