Functional characterization of a grape heat stress transcription factor VvHsfA9 in transgenic Arabidopsis

Plant heat stress transcription factor (HSF) family consists of a group of proteins participating in various signal transduction processes. However, only little information regarding HSF genes is available in grape. In this study, we reported the functional analysis of VvHsfA9 (Vitis vinifera HsfA9) in Arabidopsis. VvHsfA9 and HaHsfA9 (Helianthus annuus HsfA9) shared 34.72 % identity over the whole amino acid sequence. We discovered that the C-terminal part (VvHsfA9262–340) is required for the transcriptional activation activity of VvHsfA9. Overexpression of VvHsfA9 in Arabidopsis confers enhanced seed germination under unstressed conditions and late-flowering phenotypes. However, no other stress tolerance was observed during post-germination stage. These results suggest that VvHsfA9 functions as a seedspecific transcription factor in positive modulation of seed germination and may negatively regulate flowering time of plants.