Location: Grape Genetics Research
Title: Genetic and protein sequence variation of CBF1-4 in cold hardy wild grapevine germplasm Authors
|Garris, Amanda -|
Submitted to: Vitis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 17, 2014
Publication Date: N/A
Interpretive Summary: Grapevine production is limited by environmental conditions such as drought and low temperature. Certain species of wild grapevine (e.g. Vitis riparia) are able to tolerate very cold temperatures. A common gene pathway which contributes to survival under harsh environmental conditions is the C-repeat Binding Factor (CBF) gene pathway. In grapevine, 4 different CBF genes have been identified. The purpose of this study was to evaluate levels of DNA and amino acid variation at these gene loci in order to better understand how different grapevine species survive in different environments. Results of the study demonstrate that genetic and protein sequence variation at the Vitis CBF gene loci is very high. Variation was lowest at the CBF4 locus, the gene believed to be important for survival under low temperatures, and tests of neutrality suggest a history of selection acts to prevent amino acid changes in the CBF4 protein. Because of the low level of variation, almost all of the grapevine samples we examined shared one of two protein alleles. This result indicates that differences in low temperature survival are not due to differences in DNA or protein sequence. Instead, differences in gene expression or genes that function downstream of the CBF genes must convey variation in low temperature survival.
Technical Abstract: C-repeat Binding Factor (CBF) genes occupy a central role in the best known example of a cold regulated gene cascade in plants. CBF genes have been identified in all plants to date, although copy number and function vary by species. Studies have shown that there are at least 4 different CBF genes in the genus Vitis. Vitis(V)CBF 1, 2, and 3 are up-regulated following exposure to dehydration, salt, and chilling stresses, whereas VCBF 4 is up-regulated only after chilling. Previous studies which examined the differences in gene expression between VCBF4 in V. vinifera (cold sensitive) and V. riparia (cold tolerant) did not detect any differences despite different phenotypes. A broader survey of genetic variation at the VCBF loci may reveal polymorphisms or amino acid substitutions that contribute to differences in cold hardiness. The objective of this study was to quantify the levels of genetic and protein sequence variation for the CBF gene family within and between different species of the genus Vitis. Results indicate a greater amount of genetic and protein level sequence variation at VCBF1, 2 and 3 than at VCBF4. Variation at these three loci tended to follow species level grouping, with similarity shared within species. Variation at the VCBF4 loci was greatly reduced and the vast majority of wild Vitis accessions shared one of two major protein alleles. This result indicates that neither genetic or protein level sequence variation at the VCBF4 locus can explain phenotypic variation in cold tolerance in wild Vitis. Future studies should focus on evaluating the expression profiles and genetic variation of genes downstream of this major cold tolerance regulator.