Identification and characterisation of the Bcvic1 and Bcvic2 vegetative incompatibility genes in Botrytis cinerea

Abstract

Vegetative incompatibility (VI) is a fungal non-self recognition system characterised by the inability of genetically distinct conspecific fungal strains to form a viable heterokaryon, and is controlled by multiple polymorphic loci termed vic (vegetative incompatibility) or het (heterokaryon incompatibility). In this thesis, I report the first vic locus that has been genetically identified and characterised in the economically important plant pathogenic, necrotrophic fungus Botrytis cinerea. A bulk segregant approach coupled with whole genome Illumina sequencing was used to map a 60-kb genomic region for the vic locus in near isogenic lines of interacting compatible and incompatible strains of B. cinerea. Within that locus, I identified two adjacent highly polymorphic open reading frames encoding predicted proteins that contain domain architectures implicated in VI in other filamentous fungi, Bcvic1 and Bcvic2. Bcvic1 encodes a predicted protein containing the NACHT family of NTPases, Ankyrin repeats and a putative serine esterase. Bcvic2 encodes a putative syntaxin protein containing a SNARE domain, which functions in vesicular transport. Deletion of Bcvic1 and Bcvic2 individually did not have any effect on vegetative incompatibility. However, deletion of the region containing both Bcvic1 and Bcvic2 resulted in gene deletion lines that were severely restricted in growth and also showed loss of VI. Complementation of these mutants by ectopic expression restored the growth and vegetative incompatibility phenotype indicating that Bcvic1 and Bcvic2 are interacting and controlling VI at this vic locus.