Exploration of mlo-based resistance in vegetable crops

The plant Mlo gene family encodes heptahelical transmembrane proteins. The barley Mlo gene was discovered first and its presence found to be required for powdery mildew pathogenesis. Later it was shown that this requirement is conserved among plants. The PhD thesis is focused on exploration of the mlo-based resistance in Solanaceous crops and on understanding its associated pathways by using Arabidopsis mutants. In total, 16 tomato Mlo homologs were identified by using the whole genome sequence of tomato. Full length cDNA sequences of the identified SlMlo homologues were obtained from different tissues of tomato. Phylogenetic analysis of Mlo members (including ones from other plant species) showed that four tomato SlMlo homologues are belonging to the mildew effective clade. Expression studies upon mildew infection had been performed to understand the role of these SlMlo homologues in the defence modulation and RNAi plants were generated to study the functions of the identified SlMlo homologues to powdery mildew fungus. In order to investigate whether loss of function in Mlo homologues induces resistance to powdery mildew in pepper, the infection process of Leveillula taurica was investigated. A new pepper Mlo gene namely CaMlo2 was isolated and functional analyzed via virus-induced gene silencing. Results demonstrated that knocking down the expression of CaMlo gene resulted in reduced susceptibility of pepper to L. taurica.Regarding to defence pathways required for mlo-based resistance, we used Arabidopsis mlo-mutants and found that the impairment of PEN-dependent defence pathways did not compromise mlo-based resistance. In contrast to previous studies, our results showed that resistance of Atmlo2 mutant required the correct functioning of SA signalling.