Genomic identification, phylogeny, and expression analysis of MLO genes involved in susceptibility to powdery mildew in Fragaria vesca

Abstract

ABSTRACT. The MLO (powdery mildew locus O) gene family is important in resistance to powdery mildew (PM). In this study, all of the members of the MLO family were identified and analyzed in the strawberry (Fragaria vesca) genome. The strawberry contains at least 20 members of the MLO family, and the protein sequence contained between 171 and 1485 amino acids, with 0-34 introns. Chromosomal localization showed that the MLOs were unevenly distributed on each of the chromosomes, except for chromosome 4. The greatest number of MLOs (seven) was found on chromosome 3. A phylogenetic tree showed that the MLOs were divided into seven groups (I-VII), four of which consisted of MLOs from strawberry, Arabidopsis thaliana, rice, and maize, suggesting that these genes may have evolved after the divergence of monocots and dicots. Multiple sequence alignment showed that strawberry MLO candidates related to powdery mildew resistance possessed seven highly conserved transmembrane domains, a calmodulin-binding domain, and two conserved regions, all of which are important domains for powdery mildew resistance genes. Expressed sequence tag analysis revealed that the MLOs were induced by multiple abiotic stressors, including low and high temperature, drought, and high salinity. These findings will contribute to the functional characterization of MLOs related to PM susceptibility, and will assist in the development of disease resistance in strawberries.

Genome-Wide Identification and Characterization of MLO Gene Family in Octoploid Strawberry (Fragaria ×ananassa)

“…Three truncated MLO proteins were identified as putative pseudogenes (Table S2). The number of predicted MLO genes in diploid strawberry agrees with the previous characterization of strawberry MLO genes using the first F. vesca draft genome 25 .…”

“…This variation was also observed in previous genome-wide MLO studies in other Rosaceous crops such as apple and peach 35 . Phylogenetic analysis grouped strawberry MLO genes into eight different clades, which is consistent with previously classified MLO gene families in diploid strawberry 25 and other Rosaceous crops 35 . Functional MLO genes associated with PM resistance are grouped in clade IV and V for monocots and dicots, respectively 13 .…”

Identification and Expression Analysis of Fragaria Vesca MLO Genes Involved in Interaction with Powdery Mildew (Podosphaera Aphanis)

“…In this study, it was observed that the number of FvMLO genes and clade numbering of the FvMLO gene family were in contrast to the previously categorized FvMLO genes. Pessina, et al [15] identified 17 FvMLO genes (FvMLO1-FvMLO17) based on sequence information of tomato SlMLO1 amino acid and HMMER programme, whereas Miao, et al [38] reported 20 MLO genes in the strawberry genome (FvMLO01-FvMLO20) using Arabidopsis thaliana and rice MLO protein sequences. Further, the phylogenetic analysis in their studies showed that MLOs were grouped into seven distinct clades.…”

“…vesca accession Hawaii 4 [37] allows a comprehensive overview of the strawberry MLO gene family. A few studies have previously reported the identification of FvMLO genes in the F. vesca genome sequence [15,38]; however, the level of expression of these genes in response to disease pressure has not been studied. In the present study, we identified FvMLO genes in the F. vesca genome based on the sequence information of the Prunus americana MLO YW is reported to be susceptible to powdery mildew [39].…”

Comparative analyses of phytochelatin synthase (PCS) genes in higher plants

“…The seven-transmembrane domain proteins were homologues of barley mildew resistance locus o (MLO) and were localized in the plasma membrane [71]. The MLO gene family has been reported to be crucial in the resistance to the powdery mildew disease [72]. Calcium-dependent protein kinases have been reported to be present in all plants.…”