Anthocyanin Production in Grape Berry Skins

This is a follow up blog to my recent blog Why is Red Wine Colored Red. Now I'm going to get into the weeds regarding the genes that control anthocyanin production. In the previous blog, I wrote that anthocyanin production begins with the amino acid phenylalanine and the main point of control of anthocyanin production in the grape berry is after leucoanthocyanidin dioxygenase or LDOX. The committed step for anthocyanin production was dependent upon the enzyme UDP glucose flavonoid 3-o-glucosyl transferase or UFGT. UFGT was only detected in the berry skin and was always associated with anthocyanin accumulation.
Some elegant work done by Boss et al. in 1996 using Shiraz showed the expression of the Flavonoid Pathway genes in the following grapevine locations:

• Young leaf
• Mid leaf
• Old leaf
• Tendril
• Green cane
• Root
• Seed
• Flower
• Berry skin
• Berry flesh

Boss et al. used the northern blot to show the expression of the mRNA that code for the enzymes involved in the conversion of the substrates in the Flavonoid Pathway. By comparing the schematic of the anthocyanin pathway on the left with the Northern blot analysis on the right, it is clear that anthocyanin is produced only in the grape berry skin.

With the exception of Teinturier Grape Varieties, whose flesh is also colored red, red grape varieties of contain anthocyanins only in their skins.
References:
1. Boss PK, Davies C, Robinson SP, Expression of anthocyanin biosynthesis pathway genes in red and white grapes, Plant Mol Biol., 1996, Nov32(3):565-9.
2. Douglas Adams, VI257, Lesson 8, pg. 23.
3. Boss P, Davies C, Robinson S (1996b), "Expression of anthocyanin biosynthesis pathway genes in red and white grapes", Plant Mol Biol, 32:565 - 569.
4. Lijavetzky et al., 2006, Mol. Genet. Genomics, 2006: 427-435.
5. José Tomás Matus, Felipe Aquea and Patricio Arce-Johnson, BMC Plant Biology, 2008, 8:83.