Genetic and genomic analysis identifies bcltf1 as the transcription factor coding gene mutated in field isolate Bc116, deficient in light responses, differentiation and pathogenicity in botrytis cinerea

Abstract

[EN]Natural populations provide valuable information and resources for addressing the genetic characterization of biological systems. Botrytis cinerea is a necrotrophic fungus that exhibits complex responses to light. Physiological analysis of B. cinerea populations from vineyards in Castilla y León (Spain) allowed for the identification of isolate Bc116. This field isolate shows a reduced pathogenicity that is conditioned by the light regime. Light also delays germination and accentuates the negative effect it exerts on the vegetative growth of B. cinerea. Bc116 also displays a marked hyperconidiation phenotype and a characteristic sclerotia production pattern. Genetic analysis demonstrates that the alternative phenotypes regarding pathogenicity, conidiation, and pattern of sclerotia production co-segregate in the progeny of crosses between isolate Bc116 and a wild-type field isolate, Bc448, showing that they are under the control of a single locus. By applying a strategy based on bulked segregant analysis, the mutation in Bc116 has been mapped to a 200 kb region on Chr14 and the analysis of this region identifies a 2 kb deletion affecting the bcltf1 gene, encoding the B. cinerea Light Responsive Transcription Factor 1 described in the reference isolate B05.10. Transformation of Bc116 with the B05.10 bcltf1 allele restored the wild-type phenotypes, providing functional evidence that the natural mutant Bc116 is altered in gene bcltf1. This study offers additional information, derived from the analysis of the genetic background of a natural mutant, on the physiological processes regulated by BcLTF1 and supports the key role of this TF in the pathogenicity and photobiology of B. cinerea.