Understanding the regulation of VvDXS gene expression

Some of the most relevant wine odor constituents are monoterpenoids which have been demonstrated to be produced via the plastid-located methyl-erythritol-phosphate (MEP) pathway in grapevine. The MEP pathway biosynthetic gene 1-deoxy-D-xylulose 5-phosphate synthase (VvDXS), maps to a major QTL responsible for monoterpenoid accumulation in Muscat grape varieties. Recent results suggest that gain-of-function mutations that affect the enzymatic or regulatory properties of the VvDXS protein appear to be the major determinants of terpenoid accumulation. The 5’upstream region of VvDXS alleles was cloned and sequenced, promoter characterization was performed and several cis-elements putatively involved on the regulation of the gene were identified. The information was used to screen a transcription factor library using a transient expression dual-luciferase assay in tobacco. It is also known that genomic DNA can be compacted into chromatin to form limit accessibility of transcription factor binding to DNA target elements. Antibodies that recognize specific histone amino acid methylation patterns that are associated to the heterochromatin or the euchromatin allow us to determine the DNA modification profile. Preliminary results suggest that chromatin changes within the coding region or promoters of VvDXS gene, and this varies depending on grapevine variety and stage of berry development. Furthermore, two clones of Chardonnay that exhibit dramatic differences in monoterpenoid accumulation and berry flavor have been characterized. They represent an ideal comparison to identify rare alleles of genes controlling biosynthesis of aromatic compounds