Abstract
Flavonoids are regarded as one of the most important determinants of quality in red grapes and wines. Anthocyanins, proanthocyanidins and flavonols, are synthesized via the flavonoid pathway and share many core steps in their biosynthesis. Anthocyanins are responsible for the color of red-skinned grapes. At the onset of ripening, referred to in viticulture as veraison, color development is initiated, in part, via several members of the Myb family transcription factors. For example, MybA1 induces UFGT gene transcription leading to anthocyanin biosynthesis (Kobayashi et al. 2002). The variation in color among different grape varieties is determined by the total amount and relative proportion of cyanidinand delphinidin-based anthocyanins. Structural genes that code for two flavonoid hydroxylases, flavonoid 3’-hydroxylase (F3’H) and flavonoid 3’,5’-hydroxylase (F3’5’H), are responsible for producing the cyanidin and delphinidin precursors, respectively (Bogs et al. 2006; Castellarin et al. 2006). We analyzed a panel of nine grape cultivars that included extreme phenotypes for berry color, ranging from green (absence of anthocyanins) to red, purple and blue. The expression profiles of genes involved in flavonoid biosynthesis and storage were analyzed by qPCR at four developmental stages from before the onset of ripening to full maturity, and the total amount of anthocyanin, and anthocyanin profile, were determined (Fig. 1A, B, C, D, E, F). Color variation conforms to a particular pattern of genotype-specific expression that includes the whole of anthocyanin biosynthetic genes. Total anthocyanin amount at full maturity correlates with the cumulative expression of several structural genes of the flavonoid pathway, i.e. UFGT among others (Fig. 1C). Moreover, the anthocyanin profile, expressed as the percentage of total anthocyanins that are tri-hydroxylated anthocyanins (delfinidin, petunidin, and malvidin), was related to the ratio of F3’5’H / UFGT transcription (Fig. 1F). Clearly, with regard to berry color there is a tight coupling between transcript level, metabolite concentration, and phenotype. Environmental conditions have profound effects on flavonoid content during fruit development and ripening. In the current study, the effects of plant water status on flavonoid biosynthesis were investigated in two environments (Udine, Italy; Dunnigan Hills, California), during three seasons (2004, 2005, and 2006), on two different genotypes (Merlot and Cabernet Sauvignon). Anthocyanin biosynthesis was enhanced under drought conditions (Fig. 2A, 3A) while limited effects were observed on proanthocyanidins concentrations (Fig. 4A). These results are reflected in the expression of core structural genes of the flavonoid pathway when compared with those specific to the biosynthesis of proanthocyanidins. LDOX, a core structural gene, was significantly up-regulated under water deficit (Fig. 4B); the expression of BAN and LAR, two genes specific to proanthocyanidin biosynthesis, were insensitive to water deficit (Fig. 4C, D). The majority of structural and regulatory genes of the flavonoid pathway, including UFGT, MybA1, and LDOX (Fig 2C, D, E, F, 3C, 4B), showed a pattern of increased transcript accumulation under water deficit. The increase in total anthocyanin content observed in stressed plants resulted predominantly from an increase of 3’,4’,5’ hydroxylated forms, through the differential regulation of F3’H and F3’5’H (Fig. 3B, D). When water deficit was applied before the onset of anthocyanin accumulation, the up-regulation of these genes was maintained long after the plants were re-watered and released from the stress. Although, the specific signaling pathways through which water deficit stimulates anthocyanin production have not been elucidated, there is evidence that ABA, sugars, and brassinosteroids all play a role in the control of the onset of ripening in grape (among the others: Davies et al. 1997; Gollop et al. 2002, Symons et al. 2006). In this work, the transcription of a gene involved in brassinosteroid biosynthesis was up-regulated under water deficit (Fig. 5A, B), and at the onset of ripening, NCED1 and NCED2, genes responsible for the biosynthesis of ABA, were transiently up-regulated under water deficit (Fig. 5C, D, E, F). Taken together these results suggest the involvement of ABA and brassinosteroids in mediating the changes observed under water deficit, and furthermore, that water deficit results in an induction of ripening-related processes in general. A more detailed presentation of these studies can be found in: Castellarin et al. 2007a, b, c.
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Claims 13
Claim · model-written summary
Berry color variation followed genotype-specific expression of anthocyanin biosynthetic genes.
VitisNot reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Color variation conforms to a particular pattern of genotype-specific expression that includes the whole of anthocyanin biosynthetic genes.”
t0“grapevine berry”
Claim · model-written summary
Total anthocyanin at maturity correlated with cumulative structural-gene expression.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total anthocyanin amount at full maturity correlates with the cumulative expression of several structural genes of the flavonoid pathway, i.e. UFGT among others”
t0“grapevine berry”
Claim · model-written summary
The tri-hydroxylated anthocyanin share related to the F3’5’H / UFGT transcription ratio.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the anthocyanin profile, expressed as the percentage of total anthocyanins that are tri-hydroxylated anthocyanins (delfinidin, petunidin, and malvidin), was related to the ratio of F3’5’H / UFGT transcription”
t0“grapevine berry”
Claim · model-written summary
Drought enhanced anthocyanin biosynthesis.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Anthocyanin biosynthesis was enhanced under drought conditions”
t0“grapevine berry”
Claim · model-written summary
Drought had limited effects on proanthocyanidin concentration.
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“limited effects were observed on proanthocyanidins concentrations”
e1“Anthocyanin biosynthesis was enhanced under drought conditions”
t0“grapevine berry”
Claim · model-written summary
Water deficit significantly up-regulated LDOX.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“LDOX, a core structural gene, was significantly up-regulated under water deficit”
t0“grapevine berry”
Claim · model-written summary
BAN and LAR expression was insensitive to water deficit.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the expression of BAN and LAR, two genes specific to proanthocyanidin biosynthesis, were insensitive to water deficit”
t0“grapevine berry”
Claim · model-written summary
Most flavonoid structural and regulatory genes accumulated more transcript under water deficit.
- Treatment
- water deficite0
- Gene
- UFGT, MybA1, and LDOXe0
- Outcome
- transcript accumulatione0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The majority of structural and regulatory genes of the flavonoid pathway, including UFGT, MybA1, and LDOX (Fig 2C, D, E, F, 3C, 4B), showed a pattern of increased transcript accumulation under water deficit.”
t0“grapevine berry”
Claim · model-written summary
The anthocyanin increase in stressed plants was predominantly from 3’,4’,5’ hydroxylated forms.
- Treatment
- stressed plantse0
- Gene
- F3’H and F3’5’He0
- Outcome
- 3’,4’,5’ hydroxylated formse0
- Direction
- increasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The increase in total anthocyanin content observed in stressed plants resulted predominantly from an increase of 3’,4’,5’ hydroxylated forms, through the differential regulation of F3’H and F3’5’H”
t0“grapevine berry”
Claim · model-written summary
Gene up-regulation induced before anthocyanin accumulation persisted after rewatering.
- Organ / stage
- before the onset of anthocyanin accumulatione0
- Treatment
- water deficite0
- Outcome
- up-regulation of these genese0
- Direction
- maintainede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When water deficit was applied before the onset of anthocyanin accumulation, the up-regulation of these genes was maintained long after the plants were re-watered and released from the stress.”
t0“grapevine berry”
Claim · model-written summary
A brassinosteroid-biosynthesis gene was up-regulated under water deficit.
- Treatment
- water deficite0
- Outcome
- transcription of a gene involved in brassinosteroid biosynthesise0
- Direction
- up-regulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the transcription of a gene involved in brassinosteroid biosynthesis was up-regulated under water deficit”
t0“grapevine berry”
Claim · model-written summary
NCED1 and NCED2 were transiently up-regulated by water deficit at ripening onset.
- Organ / stage
- onset of ripeninge0
- Treatment
- water deficite0
- Gene
- NCED1 and NCED2e0
- Outcome
- transiently up-regulatede0
- Direction
- up-regulatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at the onset of ripening, NCED1 and NCED2, genes responsible for the biosynthesis of ABA, were transiently up-regulated under water deficit”
t0“grapevine berry”
Claim · model-written summary
The authors suggest ABA and brassinosteroids mediate water-deficit changes and induce ripening processes.
- Treatment
- water deficite0
- Compound
- ABA and brassinosteroidse0
- Outcome
- ripening-related processese0
- Direction
- inductione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“these results suggest the involvement of ABA and brassinosteroids in mediating the changes observed under water deficit, and furthermore, that water deficit results in an induction of ripening-related processes in general”
t0“grapevine berry”
The same questions in other papers
drought · quality: phytochemicals · VitisResults differ
11 papers in the same direction as this paper · 5 in the opposite direction
- negative
- negative
- no effect
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See all 17 papers →drought · molecular: expression · VitisPositive and negative results
11 papers in the same direction as this paper · 6 in the opposite direction
- no effect
- negative
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See all 18 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.