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

Abstract

Strawberry powdery mildew, caused by Podosphaera aphanis is a major fungal disease that affects strawberry yield and quality. In the model plant species Arabidopsis and the crop plants barley, tomato and pea, the Mildew resistance locus O (MLO) proteins have been found to be required for powdery mildew susceptibility.The present study, based on the sequence of a wild plum (Prunus americana) MLO protein, identified 16 MLO genes within the genome of woodland strawberry, Fragaria vesca and examined their expression pattern in response to powdery mildew infection in three diploid strawberry cultivars. Phylogenetic analysis showed that the FvMLO genes can be classified into six clades. Four FvMLO genes were grouped into clade III, which comprises MLO genes from Arabidopsis, tomato and grapevine that mediate powdery mildew susceptibility. A RNA-seq analysis of two diploid strawberry cultivars, F. vesca ssp. vesca accession Hawaii 4 (HW) and F. vesca f. semperflorens line "Yellow Wonder 5AF7" (YW) at 1 d (1 DAI) and 8 d (8 DAI) after infection showed the expression of 12 out of the 16 FvMLO genes. The comparison of Fragments Per Kilobase of transcript per Million mapped reads (FPKM values) detected by RNA-seq and expression values of qRT-PCR for FvMLO genes showed substantial agreement. The FvMLO3 gene, which was grouped in clade III and orthologous to the Arabidopsis, tomato and grapevine genes, was highly expressed in YW compared to other FvMLO genes across varieties. The results showed that FvMLO genes can be used as potential candidates to engineer powdery mildew resistance in strawberry based on MLO suppression or genome editing.

Salicylic acid-primed defence response in octoploid strawberry ‘Benihoppe’ leaves induces resistance against Podosphaera aphanis through enhanced accumulation of proanthocyanidins and upregulation of pathogenesis-related genes

“…Transcriptome analysis has shown differentially expressed genes (DEGs) related to secondary metabolism, signal transduction, and disease resistance were upregulated and played crucial roles in the early defence against P. aphanis [18]. Furthermore, functional identification of candidate genes from the diploid strawberry has enabled the investigation of resistance to P. aphanis, including FvHsfB1a [19], FvMLO [20], and FvWRKY42 [21]. Antisense expression of PpMlo1-conferred resistance in the octoploid strawberry to P. aphanis, indicating that the Mlo-based resistance mechanism is functional in strawberry [22].…”

Identification of QTLs for powdery mildew (Podosphaera aphanis; syn. Sphaerotheca macularis f. sp. fragariae) susceptibility in cultivated strawberry (Fragaria ×ananassa)

“…Indeed, Pessina et al [10] reported that knock-down expression of the MLO gene MdMLO19 in apple reduced the susceptibility of transformed lines to powdery mildew, and Jiwan et al [11] reported that antisense expression of the peach MLO gene PpMLO1 in transgenic cultivated strawberry lines conferred resistance to Fragaria -specific powdery mildew isolates. Recently, two groups [12,13] characterised several MLO genes and pseudogenes in the genome sequence of F . vesca .…”

“…Twelve of the identified genes were expressed following challenge by isolates of powdery mildew in F . vesca accessions [13]. Two of these genes, annotated as FvH4_7g08130.1 and FvH4_7g19790.1 in the FvH4 v4.0 assembly [14], were differentially expressed in response to powdery mildew infection in F .…”

“…Two of these genes, annotated as FvH4_7g08130.1 and FvH4_7g19790.1 in the FvH4 v4.0 assembly [14], were differentially expressed in response to powdery mildew infection in F . vesca [13].…”

Salicylic acid primed defence response in octoploid strawberry (Benihoppe) leaves induces resistance against Podosphaera aphanis through enhanced accumulation of proanthocyanidins and up-regulation of pathogensis-related genes

“…Furthermore, functional identification of candidate genes from the diploid strawberry has enabled the investigation of resistance to P. aphanis. These include FvHsfB1a [19], FvMLO [20], and FvWRKY42 [21]. Antisense expression of PpMlo1 conferred resistance in the octoploid strawberry to P. aphanis, indicating that the Mlo-based resistance mechanism is functional in strawberry [22].…”