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

TL;DR

A study finds that a mutation in the bcltf1 gene in a natural strain of Botrytis cinerea causes reduced pathogenicity and altered growth under light.

Contribution

The paper identifies bcltf1 as the gene responsible for multiple mutant phenotypes in a field isolate of Botrytis cinerea using genetic and genomic analysis.

Findings

The Bc116 isolate shows reduced pathogenicity, delayed germination, and altered conidiation and sclerotia production under light.

A 2 kb deletion in the bcltf1 gene on chromosome 14 is responsible for the mutant phenotype in Bc116.

Restoring the bcltf1 gene in Bc116 restores wild-type phenotypes, confirming its functional role.

Abstract

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.

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