Silencing of a raspberry homologue ofVRN1is associated with disruption of dormancy induction and misregulation of subsets of dormancy-associated genes

Abstract

ABSTRACTWinter dormancy is a key process in the phenology of temperate perennials. The changing climate is severely impacting its course leading to economic losses in agriculture. A better understanding of the underlying mechanisms, as well as the genetic basis of the different responses, are necessary for the development of climate-resilient cultivars. This study aims to provide an insight into winter dormancy in red raspberry (Rubus idaeusL).We report the transcriptomic profiles during dormancy in two raspberry cultivars with contrasting responses. The cultivar ‘Glen Ample’ showed a typical perennial phenology, whereas ‘Glen Dee’ registered consistent dormancy dysregulation, exhibiting active growth and flowering out of season. RNA-seq combined with weighted gene co-expression network analysis (WGCNA) highlighted gene clusters in both genotypes that exhibited time-dependent expression profiles, Functional analysis of ‘Glen Ample’ gene clusters highlighted the significance of the cell and structural development prior to dormancy entry as well the role of genetic and epigenetic processes such as RNAi and DNA methylation in regulating gene expression. On the contrary, dormancy release in ‘Glen Ample’ was associated with upregulation of transcripts associated with the resumption of metabolism, nucleic acid biogenesis and processing signal response pathways.Many of the processes occurring in ‘Glen Ample’ were dysregulated in ‘Glen Dee’ and twenty-eight transcripts exhibiting time-dependent expression in ‘Ample’ that also had an Arabidopsis homologue were not found in all samples from ‘Glen Dee’. These included a gene with homology to ArabidopsisVRN1(RiVRN1.1) that exhibited a sharp decline in expression following dormancy induction in Glen Ample. Characterisation of the gene region in the ‘Glen Dee’ genome revealed two large insertions upstream of the ATG start codon. We propose that non-expression of a specific VRN1 homologue in ‘Glen Dee’ causes dormancy misregulation as a result of inappropriate expression of a subset of genes that are directly or indirectly regulated byRiVRN1.1.HIGHLIGHTThe raspberry cultivar Glen Dee exhibits aberrant winter dormancy status associated with insertions in the upstream promoter region of aVRN1(RiVRN1.1) homologue that silence expression, allowing the identification of dormancy-associated genetic modules that are regulated byRiVRN1.1.