Modulation of flavonoid biosynthetic pathway genes and anthocyanins due to virus infection in grapevine (Vitis vinifera L.) leaves

BMC Plant Biol. 2010 Aug 23;10:187. doi: 10.1186/1471-2229-10-187.


Background: Symptoms of grapevine leafroll disease (GLRD) in red-fruited wine grape (Vitis vinifera L.) cultivars consist of green veins and red and reddish-purple discoloration of inter-veinal areas of leaves. The reddish-purple color of symptomatic leaves may be due to the accumulation of anthocyanins and could reflect an up-regulation of genes involved in their biosynthesis.

Results: We examined six putative constitutively expressed genes, Ubiquitin, Actin, GAPDH, EF1-a, SAND and NAD5, for their potential as references for normalization of gene expression in reverse transcription-quantitative real-time polymerase chain reaction (RT-qPCR). Using the geNorm program, a combination of two genes (Actin and NAD5) was identified as the stable set of reference genes for normalization of gene expression data obtained from grapevine leaves. By using gene-specific RT-qPCR in combination with a reliable normalization factor, we compared relative expression of the flavonoid biosynthetic pathway genes between leaves infected with Grapevine leafroll-associated virus 3 (GLRaV-3) and exhibiting GLRD symptoms and virus-free green leaves obtained from a red-fruited wine grape cultivar (cv. Merlot). The expression levels of these different genes ranged from two- to fifty-fold increase in virus-infected leaves. Among them, CHS3, F3'5'H, F3H1, LDOX, LAR1 and MybA1 showed greater than 10-fold increase suggesting that they were expressed at significantly higher levels in virus-infected symptomatic leaves. HPLC profiling of anthocyanins extracted from leaves indicated the presence of cyanidin-3-glucoside and malvidin-3-glucoside only in virus-infected symptomatic leaves. The results also showed 24% higher levels of flavonols in virus-infected symptomatic leaves than in virus-free green leaves, with quercetin followed by myricetin being the predominant compounds. Proanthocyanidins, estimated as total tannins by protein precipitation method, were 36% higher in virus-infected symptomatic leaves when compared to virus-free green leaves.

Conclusions: The results, the first example to our knowledge, showed that modulation of the flavonoid biosynthetic pathway occurred in GLRaV-3-infected leaves of a red-fruited wine grape cultivar (cv. Merlot) leading to de novo synthesis of two classes of anthocyanins. These anthocyanins have contributed to the expression of reddish-purple color of virus-infected grapevine leaves exhibiting GLRD symptoms.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Anthocyanins / biosynthesis*
  • Anthocyanins / metabolism
  • Biosynthetic Pathways / genetics
  • Closteroviridae
  • Flavonoids / biosynthesis*
  • Flavonols / metabolism
  • Fruit / genetics
  • Fruit / metabolism
  • Gene Expression
  • Gene Expression Regulation, Plant
  • Genes, Plant*
  • Glucosides / metabolism
  • Plant Diseases / virology*
  • Plant Leaves / genetics
  • Plant Leaves / metabolism
  • Plant Leaves / virology
  • Proanthocyanidins / metabolism
  • Transcription, Genetic
  • Up-Regulation
  • Vitis / genetics
  • Vitis / metabolism
  • Vitis / virology*


  • Anthocyanins
  • Flavonoids
  • Flavonols
  • Glucosides
  • Proanthocyanidins
  • cyanidin-3-O-beta-glucopyranoside
  • malvidin-3-glucoside
  • myricetin