COMPARATIVE GENETIC AND METABOLIC CHARACTERIZATION BETWEEN TWO TABLE GRAPE VARIETIES WITH CONTRASTED COLOR BERRY SKIN: RED GLOBE AND CHIMENTI GLOBE
Comparative genetic and metabolic characterizatión between two table grape varieties with contrasted color berry skin: red globe and chimenti globe
Autor
Arce-Johnson, Jorge Patricio
Gomès, Eric
PONTIFICIA UNIVERSIDAD CATOLICA DE CHILE
Institución
Resumen
Grape berry development is a dynamic process exhibiting a double sigmoid curve separated by a lag phase, characterized by coordinated biosynthesis of primary and secondary metabolites. At the end of lag phase, a phenomenon called veraison occurs, where the fruit begins to take color and maturation process is initiated. Anthocyanins are the responsible of berry skin coloration and its regulation has been widely studied. However, few studies have focused on metabolic and genetic characterization using varieties with contrasted color berry skin. Using RNA-seq technology and metabolic analysis, we performed a new comparative characterization of two table grapes, Chimenti Globe (CG) and Red Globe (RG), with contrasted color berry skin: CG has a bright light red color and RG has a dark purple color. The originality of this model is that CG was generated from a spontaneous event in field from a branch in a vine of RG plant. Thus, the genetic background responsible for the color change is practically the same. Berry metabolic content analysis showed the importance of veraison and ripening stages, in both varieties in the study. Particularly, striking difference in metabolites concentration of phenylpropanoid pathway: shikimate, UDP-glucose, phenylalanine and trehalose-6-phosphate, among others. Also, differences between the varieties were due to changes in metabolites related to the biosynthesis of sucrose and anthocyanin. CG only contained dihydroxylated anthocyanins, peonidin and cyanidin, and not the trihydroxylated ones, malvidin, delphinidin and petunidin, which was consistent with the observed color phenotype. From transcriptomic analysis, we generated a heat map with 109 genes differentially expressed in CG in comparison to RG, being many of these related to the flavonoid pathway. In addition, 11 gene copies of flavonoid 3’5’-hydroxylase, a key enzyme for biosynthesis of trihydroxylated anthocyanins, were not induced in CG. From this analysis, we selected a candidate gene to contribute in the study of the anthocyanin biosynthetic pathway: Cytochrome b5 (Cytb5) encoding a key electron donor protein not characterized in grapevine. Cytb5 overexpression in V. berlandieri x V. Rupestris 110R embryos strongly suggested its participation in the pathway, since transgenic embryos exhibited reddish color and in addition, an accelerated development compared to control. With these results, we were able to provide new insights in anthocyanins regulation in grapevines responsible for berry skin coloration, opening new fields in the search for molecular regulators of the flavonoid pathway.