Expression of Basic Helix-Loop-Helix Transcripts During Low Temperature Treatments in Grapevines

The differential expression of six basic helix-loop-helix (bHLH) genes in response to low temperatures was studied by evaluating their mRNA levels in the buds and shoots of grapevines. Comparison of the amino acid sequences deduced from nucleotide sequences of the bHLH genes in Vitis labruscana transcripts revealed homologies ranging from 58.8% (VlCEbHLH1 and VlCEbHLH4) to 8.2% (VvbHLH and VlCEbHLH3). Specific primers from unique regions of genes were obtained by alignment of nucleotide sequences and used to evaluate differential expression patterns of bHLH genes. The accumulation patterns of bHLH mRNAs were induced differentially and dependent on the treated temperatures, -20°C in the buds and -2°C and 4°C in the shoots of ‘Campbell Early’ and ‘Muscat Baily A’ grapevines. The bHLH genes showed differential expression patterns in response to low temperatures. In ‘Campbell Early’, the expression of VlCEbHLH1, VlCEbHLH2, and VlCEbHLH5 was up-regulated, while VlCEbHLH3 was down-regulated in response to -20°C cold stress. In ‘Muscat Bailey A’, the expression of all genes was rapidly up-regulated, peaking at 6 h, then decreasing at 12 h after treatment.