Characterization of the core region of grape VvHOS1 promoter activity and its upstream regulatory proteins

The tropical origins of the grape (Vitis vinifera L.) make it vulnerable to low temperatures, which constitute a serious threat to grape production. Our knowledge of the molecular basis of cold tolerance in perennial grape species is limited. The E3 ubiquitin ligase HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE 1 (HOS1) has been demonstrated to negatively regulate cold responsiveness, but the understanding of the HOS1 in grape remains fragmentary. Here, we initially evaluated the expression of HOS1 in cold-tolerant Vitis amurensis (VaHOS1) and susceptible V. vinifera (VvHOS1) cultivars and discovered their responses to cold stress differed significantly. The two grape HOS1 genes exhibit a high degree of sequence similarity (98.77% at the amino acid level) but their lengths (313-bp insertion/deletion polymorphism) and promoter sequences are substantially different (91.96%). This 313-bp region significantly affects the differential expression of HOS1 between V. vinifera and V. amurensis. The 313-bp deletion abolished VvHOS1 promoter activity in promoter-GUS assay of transgenic Arabidopsis. Moreover, 313-bp fragment might function as a positive core region to affect promoter activity of VvHOS1 to involved in different developmental stages and cold stress. In addition, DNA pull-down and mass spectrometry (MS) assay revealed the potential regulatory proteins may bind to the 313-bp core promoter region. We show that the two linker histone H1 genes (designated as VvHH1: LOC100853898 and LOC100259836), and one sister chromatid cohesion protein PDS5 homolog B (designated as VvPDS5B: LOC100853350), which associates with the core promoter region, decreases or activates GUS expression. This work elucidates the expression features of the HOS1 promoter from genus Vitis and further identifies a core region required for the promoter activity via trans-activation or suppression of candidate regulatory proteins.