Transcriptional control of anthocyanin biosynthetic genes in extreme phenotypes for berry pigmentation of naturally occurring grapevines.
BACKGROUND
Fruit coloration of red-skinned grapevines is mainly due to anthocyanin pigments. We analysed a panel of nine cultivars that included extreme phenotypes for berry colour, ranging from green (absence of anthocyanins) to red, purple, violet and blue. Expression of six genes of the anthocyanin pathway coding for flavanone-hydroxylase (F3H), flavonoid 3'-hydroxylase (F3'H), flavonoid 3',5'-hydroxylase (F3'5'H), UDP-glucose:flavonoid-3-O-glucosyltransferase (UFGT), glutathione-S-transferase (GST), O-methyltransferase (OMT) and four transcription factors (MybA, MybB, MybC, MybD) was analysed by quantitative RT-PCR at four developmental stages from before the onset of ripening until full maturity and compared to anthocyanin metabolites.


RESULTS
Total anthocyanin content at full maturity correlated well with the cumulative expression of F3H, UFGT and GST throughout ripening. Transcripts of the last two genes were absent in the green-skinned cultivar 'Sauvignonasse', also known as 'Tocai friulano', and were at least 10-fold less abundant in pale red cultivars, such as 'Pinot gris' and 'Gewürztraminer', compared to fully coloured cultivars. Predominance of tri-hydroxylated anthocyanins (delphinidin, petunidin and malvidin) in cultivars bearing dark berries with violet and blue hue was associated with higher ratios of F3'5'H/F3'H transcription, compared to red-skinned cultivars. Higher levels of OMT transcripts were observed in berries of cultivars that accumulated methoxylated forms of anthocyanins more abundantly than non-methoxylated forms.


CONCLUSIONS
Colour variation of the grape berry conforms to a peculiar pattern of genotype-specific expression of the whole set of anthocyanin genes in a direct transcript-metabolite-phenotype relationship. Cumulative mRNA levels of the structural genes and their relative abundance throughout ripening explained per se the final phenotype for anthocyanin content, anthocyanin composition, colour intensity and colour hue of grapes at berry maturity.
Castellarin
Simone D
SD
Istituto di Genomica Applicata, Parco Scientifico e Tecnologico Luigi Danieli, via Jacopo Linussio 51, 33100 Udine, Italy. simone.castellarin@uniud.it
Di Gaspero
Gabriele
G
D000872:Anthocyanins / Q000096:biosynthesis* / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D005638:Fruit / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010858:Pigmentation / Q000235:genetics*; D019441:Plant Epidermis / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011497:Protein O-Methyltransferase / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic; D027843:Vitis / Q000235:genetics / Q000378:metabolism*
D000872:Anthocyanins; D010940:Plant Proteins; D014157:Transcription Factors; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; C084258:flavonoid 3',5'-hydroxylase; C038888:flavonoid 3'-hydroxylase; D011497:Protein O-Methyltransferase; D005982:Glutathione Transferase