Identification of grapevine MLO gene candidates involved in susceptibility to powdery mildew

Abstract

The European cultivated grapevine, Vitis vinifera L., is a host for the powdery mildew pathogen Erisyphe necator, which is the most economically important fungal disease of viticulture. MLO proteins mediate powdery mildew susceptibility in the model plant species Arabidopsis and the crop plants barley and tomato. Seven VvMLO cDNA sequences were isolated from grapevine and were subsequently identified as part of a 17 member VvMLO gene family within the V. vinifera genome. Phylogenetic analysis of the 17 VvMLO genes in the grape genome indicated that the proteins they encode fall into six distinct clades. The expression of representative VvMLOs from each clade were analysed in a range of grape tissues, as well as in response to a range of biotic and abiotic factors. The VvMLOs investigated have unique, but overlapping tissue expression patterns. Expression analysis of VvMLO genes following E. necator infection identified four upregulated VvMLOs which are orthologous to the Arabidopsis AtMLO2, AtMLO6 and AtMLO12 and tomato SlMLO1 genes required for powdery mildew susceptibility. This suggests a degree of functional redundancy between the proteins encoded by these genes in terms of susceptibility to powdery mildew, and, as such, represent potential targets for modification to generate powdery mildew resistant grapevines.

Genome-wide Identification, Classification and Expression Analysis of the Mildew Resistance Locus O ( MLO ) Gene Family in Sweet Orange ( Citrus sinensis )

“…2). Consistent with this finding, VvMLO14 in the dicot species grapevine, also assembles in clade IV [ 21 ]. Finally, clade VI, containing AtMLO3 and CisMLO14, which was considered as a single divergent lineage in former studies [ 21 ], more detailed functions of AtMLO3 and CisMLO14 will be revealed by the further investigation.…”

“…Consistent with this finding, VvMLO14 in the dicot species grapevine, also assembles in clade IV [ 21 ]. Finally, clade VI, containing AtMLO3 and CisMLO14, which was considered as a single divergent lineage in former studies [ 21 ], more detailed functions of AtMLO3 and CisMLO14 will be revealed by the further investigation. These results strongly indicated the existence of sweet orange-specific MLO gene that was either lost in Arabidopsis and rice or acquired in the sweet orange lineages after an evolutionary splitting event from the most recent common ancestor.…”

“…tomato and Xanthomonas campestris pv. vesicatoria [ 60,61 ]; wounding [ 21,37,62 ]; phytohormone [ 24,26,63 ] and abiotic stresses [ 63,64 ]. As a rule, however, the paralogs in MLO family, as illuminated by their clustering pattern (Fig.…”

“…Furthermore, PM resistance of pea er1 initialing from the loss of function of PsMLO1 was first reported since 1948 and is the sole resistance source internationally used for breeding objectives [ 11,19 ]. Interestingly, when displayed in the evolutionary trees of MLO protein family, all MLO isoforms from dicots experimentally shown to be necessary for PM immunity group in the clade V in the scientific documents [ [8][9][10][20][21][22] ]. Furthermore, clade IV harbors all featured monocot PM perceptivity proteins [ 23 ].…”

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

“…An MLO gene was first identified in barley [3] and currently, a varying number of MLO genes have been identified in Arabidopsis, Medicago truncatula, chickpea, rice, maize, wheat, soybean, cucumber, tomato, rose, grapevine, peach, apple, sweet orange, cultivated Solanaceae, Brachypodium, and Cucurbitaceae species respectively [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. Although the biological functions of MLO genes are not yet completely known, they act as suppressors of defense responses.…”