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Characterization of the MLO gene family in Rosaceae and gene expression analysis in Malus domestica

Stefano Pessina12, Stefano Pavan3, Domenico Catalano4, Alessandra Gallotta3, Richard GF Visser2, Yuling Bai2, Mickael Malnoy1* and Henk J Schouten2*

Author Affiliations

1 Department of Genomics and Biology of Fruit Crops, Fondazione Edmund Mach, via E. Mach 1, 38010 San Michele all’Adige, Italy

2 Wageningen UR Plant Breeding, Wageningen University and Research Centre, P.O Box 16, 6700 AA Wageningen, The Netherlands

3 Department of Soil, Plant and Food Science, University of Bari, Via Amendola 165/A, 70126 Bari, Italy

4 National Research Council, Institute of Plant Genetics, Via Amendola 165/A, 70126 Bari, Italy

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BMC Genomics 2014, 15:618  doi:10.1186/1471-2164-15-618

Published: 22 July 2014



Powdery mildew (PM) is a major fungal disease of thousands of plant species, including many cultivated Rosaceae. PM pathogenesis is associated with up-regulation of MLO genes during early stages of infection, causing down-regulation of plant defense pathways. Specific members of the MLO gene family act as PM-susceptibility genes, as their loss-of-function mutations grant durable and broad-spectrum resistance.


We carried out a genome-wide characterization of the MLO gene family in apple, peach and strawberry, and we isolated apricot MLO homologs through a PCR-approach. Evolutionary relationships between MLO homologs were studied and syntenic blocks constructed. Homologs that are candidates for being PM susceptibility genes were inferred by phylogenetic relationships with functionally characterized MLO genes and, in apple, by monitoring their expression following inoculation with the PM causal pathogen Podosphaera leucotricha.


Genomic tools available for Rosaceae were exploited in order to characterize the MLO gene family. Candidate MLO susceptibility genes were identified. In follow-up studies it can be investigated whether silencing or a loss-of-function mutations in one or more of these candidate genes leads to PM resistance.

Rosaceae; MLO; Powdery mildew; Malus domestica