Transcriptional response to temperature of ripening microvine (DRCF) depends on daytime

Transcriptional changes induced by temperature stress in ripening berries from the Dwarf Rapid Cycling and Flowering Vvgai1 mutant (DRCF) were investigated. Following a two weeks adaptation period at a constant day and night temperature couple, vines were submitted to 2 h heat stress during the day and during the night. To overcome biases in gene expression induced by the very high asynchrony in fruit ripening, berries were analyzed individually to create homogenous samples for RNA extraction. A whole transcriptome approach was conducted with Nimbelgen (R) 090918 Vitus exp HX12 oligoarrays bearing 29,582 probe sets. Samples were ranked by PCA analysis with the first 2 principal components explaining around 70% of the variation in gene expression. The first axis (temperature response) accounted for 50% of the variance between treatments. Interestingly, a major part of nycthemeral cycle responding genes loose this control upon temperature stress, while most temperature-induced genes were dependent on daytime. VvGOLS 1 and HSFA, both genes recently reported to be overexpressed upon high temperature treatments in the berry were used to validate applied stress on DRCF. They showed a high activation upon heat stress amongst numerous other heat responsive genes from other species.