Heat shock-like responses along with genetic polymorphisms associate with the pedate leaf phenotype of Chasselas Cioutat somatic variant

ROYO, C; CARBONELL BEJERANO, P; MARTINEZ-ZAPATER, JM; LIJAVETZKY, D

Verona

Simposio; XXIV Jornadas de Investigación y VI Jornadas de Posgrado de la Universidad Nacional de Cuyo; 2016

University of Verona / International Society for Horticultural Science

Somatic genetic variation constitutes an important source of phenotypic variation in grapevine. In perennial plant species where mutants are difficult to generate and screen, spontaneous somatic variants represent a unique resource to understand the genetic control of complex developmental patterns. Chasselas Cioutat is a somatic variant of cultivar Chasselas displaying pedate or parsley-like leaves. Genetic analysis of a Cioutat self-cross S1 population showed a 25% of wild-type (Chasselas) phenotype plants, consistent with the hypothesis of the phenotype being caused by a single dominant mutation. To understand the origin of this variation, transcriptome comparisons between Cioutat and Chasselas leaf primordia and shoot tips were carried out using microarray and RNA-seq assays, respectively. More than 400 differentially expressed genes were detected, most of them upregulated in Cioutat. Upregulated genes were enriched in heat shock response, ERF transcription factor, and secondary metabolism biosynthesis genes. Consistently upregulated in both transcriptome comparisons, we detected a BAG (Bcl-2 associated athanogene) gene closely related to the Arabidopsis AtBAG6 gene. We named that grapevine gene as VviBAG6. Interestingly, in Arabidopsis, AtBAG6 is suggested to be a stress upregulated co-chaperone involved in programmed cell death (PCD) and thermotolerance. Moreover, in the Cioutat S1 progeny, we detected a positive and statistically significant correlation between VviBAG6 expression level and the extension of the parsley leaf phenotype. RNA-seq data was also useful to identify SNPs distinguishing the Chasselas and Cioutat variant lines. Among 15 Cioutat-specific SNPs detected, 7 involved non-synonymous substitutions in the predicted protein. All these variant alleles were heterozygous in Cioutat, which could fit with the dominant segregation of the pedate leaf phenotype in the S1 progeny. Collectively, these results suggest the involvement of heat shock-like responses triggering PCD in the generation of the variant leaf phenotype of Cioutat and provide putative responsible genetic variants to be further tested.