engleski

Chimeric Nature of the Croatian Grapevine Variety Plavac mali sivi

The color of berry skin in grapevine was shown to be controlled by a retrotransposon-induced mutation within the promoter of the VvmybA1 locus. This locus encodes for a MYB transcription factor, which positively regulates anthocyanin biosynthesis. In red-berried grapevine varieties, the Gret1 retrotransposon is either completely absent from the VvmybA1 promoter, or it is present as a single hemizygous insertion. On the other hand, the majority of white-berried grapevine varieties have two Gret1 insertions in both VvmybA1 alleles. Pinot gris and Malian are grey- and pink-berried clones of Pinot noir and Cabernet sauvignon, respectively. Both are treated as separate grapevine varieties due to their gray or light red berry color (instead of the usual dark blue color). The characteristic phenotype arises due to a reduced number of cell layers producing anthocyanins within the berry skins. Although the molecular mechanism causing this phenotype is not jet fully elucidated, it is most likely a consequence of two genetically different cell layers coexisting within the berry skins. Plavac mali crni is a well known Croatian grapevine variety used for the production of high-quality red wines. Plavac mali sivi is its grey-berried somatic mutant, first described in the 1970’s. The genetic background of the causing mutation was unknown so far. Here we present the molecular characterization of the VvmybA1 locus in Plavac mali sivi using Gret1-specific markers as well as an IRAP multiplex approach (Inter-Retrotransposon Amplified Polymorphism). Moreover, we find evidence for a chimeric nature of the berry cell layers in Plavac mali sivi, thereby offering a possible explanation for its grey-berried phenotype. On a broader level, our findings open the question of whether it would be feasible to produce grey-berried clones of each of the existing red-berried grapevine varieties, with at least some of them possibly showing a commercial potential.

Gret1; retrotransposons; grapevine; Plavac mali

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