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

Abstract

Powdery mildew (PM) caused by Podosphaera aphanis is a major fungal disease in cultivated strawberry. Mildew Resistance Locus O (MLO) is a gene family described for having conserved seven-transmembrane domains. Induced loss-of-function in specific MLO genes can confer durable and broad resistance against PM pathogens. However, the underlying biological role of MLO genes in strawberry is still unknown. In the present study, the genomic structure of MLO genes were characterized in both diploid (Fragaria vesca) and octoploid strawberry (Fragaria ×ananassa), and the potential sources of MLO-mediated susceptibility were identified. Twenty MLO-like sequences were identified in F. vesca, with sixty-eight in F. ×ananassa. Phylogenetic analysis divides strawberry MLO genes into eight different clades, in which three FveMLO and ten FaMLO genes were grouped together with the functionally known MLO susceptibility. Out of ten FaMLO genes, FaMLO17-2 and FaMLO17-3 showed the highest similarity to the known susceptibility MLO proteins. Gene expression analysis of FaMLO genes was conducted using a multi-parental segregating population. Three expression quantitative trait loci (eQTL) were substantially associated with MLO transcript levels in mature fruits, suggesting discrete genetic control of susceptibility. These results are a critical first step in understanding allele function of MLO genes, and are necessary for further genetic studies of PM resistance in cultivated strawberry.

Genome-wide identification of the oatMLOfamily and identification of a candidateAsMLOassociated with powdery mildew susceptibility

“…However, homeologs were not found for AsMLO1, AsMLO5, AsMLO7, AsMLO9 and AsMLO11_partial . Similar to our findings, the octoploid strawberry ( Fragaria × ananassa ) had varying numbers of homeologs for each of the 20 FaMLOs identified ranging from none through to seven homeologs (Tapia et al ., 2020). Previously, the homeologs TaMlo-A1, TaMlo-B1 and TaMlo-D1 were identified in wheat which are associated with powdery mildew susceptibility (Elliot et al , 2002).…”

Genome-wide characterization of MLO family genes in bread wheat and Arabidopsis thaliana shed light on their role in growth and development, and resistance to powdery mildew, biotic and abiotic stresses

“…Several other groups reported a varying number of MLO superfamily members in different plant species. For example, 15 MLO genes were identified in Arabidopsis (Devoto et al, 2003), whereas 20 in pumpkin (Win et al, 2018), 15 in lentil (Polanco et al, 2018), seven in bread wheat (Konishi et al, 2010), 20 in strawberry (Tapia et al, 2020), 68 in octaploid strawberry (Tapia et al, 2020), 39 in soybean (Deshmukh et al, 2014) etc. As several species have 15 MLO genes therefore, wheat has 47 MLO genes being a hexaploid.…”