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.

General Phenylpropanoid/Flavonoid Pathway

On February 16th, I blogged about Why is Red Wine Colored Red and in that blog, I included this schematic of the pathway to anthocyanins that began with the amino acid phenylalanine:¹

I then found a diagram that showed a more complete schematic of the flavonoid pathway after it diverges at the point of the reaction involving 4-coumaroyl-CoA. By looking at the schematic above and comparing it to the schematic below, the point of synthesis of the three main flavonoid classes flavonols, anthocyanins, and flavan-3-ols can be discerned.²

Flavan-3-ol monomers include (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, (-)-epicatechin-3-O-gallate, and traces of (+)-gallocatechin. The oligomers and polymers of these flavan-3-ol monomers, are the most abundant flavonoids found in berries.
Why is this important:

• the most abundant flavonoids are proanthocyanidins (PAs)
• the major quality determinants for fruit and wine are the proanthocyanidins
• the total content of PAs is usually higher in seeds
• large quantities of (-)-epicatechin-3-O-gallate are located in the seeds
• the polymer size of PAs is much larger in the skin with (-)-epigallocatechin being a major skin PA subunit

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. Yung-Fen Huang, Sandrine Vialet, Jean-Luc Guiraud, Laurent Torregrosa, Yves Bertrand,Veronique Cheynier, Patrice This and Nancy Terrier, A negative MYB regulator of proanthocyanidin accumulation, identified through expression quantitative locus mapping in the grape berry, New Phytologist, (2014) 201: 795–809 doi: 10.1111/nph.12557.

2015 Paumanok Minimalist Chenin Blanc

Recently, we drank this 2015 Minimalist Chenin Blanc from Paumanok. We purchased this bottle from Paumanok when we went to visit Kareem and Charles Massoud with our own version of Chenin Blanc that we made from our harvest in 2015. It was very interesting to compare 4 different styles of Chenin Blanc. We brought over our 2015 Chenin Blanc Sec and our 2015 Chenin Blanc Sussreserve. We compared it with the 2015 Paumanok Chenin Blanc and the 2015 Paumanok Minimalist Chenin Blanc. I really enjoyed the Minimalist and tasted the stone fruit spectrum of apricots and peaches.

Why is Red Wine Colored Red

Have you ever wondered why red wine is colored red? I wrote about it in a blogpost called Anthocyanins Give Red Wine Their Color. The red color in grapes is attributable to the anthocyanins located in the grape berry skin.¹
I'm going to delve a little deeper in this blog about how anthocyanins are formed and why they end up being accumulated in the berry skin. The pathway for the formation of anthocyanins begins with the amino acid phenylalanine:²

In the diagram shown above, phenylalanine can be shunted into two pathways:

• General Phenylpropanoid Metabolic Pathway: Phenylalanine is first converted to 4-coumaroyl-CoA and this compound may be used in the production of lignins, coumarins and stilbenes
• Flavonoid Pathway: Conversion of 4-coumaroyl-CoA results in the production of a range of flavonoid compounds, the most common being aurones, flavones, flavonols, isoflavonoids, proanthocyanidins and anthocyanins.

The main point of control of anthocyanin production in the grape berry is after leucoanthocyanidin dioxygenase or LDOX. Expression of the enzyme that converts the precursor of anthocyanins, UDP glucose flavonoid 3-o-glucosyl transferase or UFGT was only detected in the berry skin and was always associated with anthocyanin accumulation. Red wines therefore, are the result of the extraction of anthocyanins from the grape berry skins and oh so much more chemistry! (Maybe in another blog)

References:
1. Douglas Adams, VI257, Lesson 8, pg. 23. All structures were drawn by the freely available drawing program from ACD Labs called ACD/ChemSketch Freeware.
2. Boss P, Davies C, Robinson S (1996b), "Expression of anthocyanin biosynthesis pathway genes in red and white grapes", Plant Mol Biol, 32:565 - 569.
3. Lijavetzky et al., 2006, Mol. Genet. Genomics, 2006: 427-435.
4. José Tomás Matus, Felipe Aquea and Patricio Arce-Johnson, BMC Plant Biology, 2008, 8:83.
5. A negative MYB regulator of proanthocyanidin accumulation, identified through expression quantitative locus mapping in the grape berry, New Phytologist, (2014) 201: 795–809 doi: 10.1111/nph.12557.

Happy Valentines Day

New Tab: Vineyard Sightings

My husband recently sent me a link to an article called Heading Toward the 'No-Touch' Vineyard, that appeared in the trade journal Wines & Vines. The article reported on the discussion by a panel of growers at this year's Unified Wine & Grape Symposium regarding their work on mechanizing vineyard operations. The panel discussed:

• unmanned aerial drones
• self-driving tractors with robotic implements
• elaborate real-time monitoring systems

The economic underpinnings of mechanization are real and compelling. One grower mentioned that a totally mechanized vineyard might be a reality in 5-10 years.
I can understand how growers with large vineyards would want to mechanize aspects of viticulture. Totally, on board. We have a tractor (although sometimes, I would like to do things with horse, that is totally a pipe dream). But one of the exciting things about having a vineyard is actually going out into the vineyard and seeing things up close.
Since we are in the middle of the blizzard of 2017, I have been going through all of the blogs that I have posted and curated them into their appropriate categories. As I went through the blogposts, I came upon many postings I wrote about but did not categorize on the cool things we saw in the vineyard as we worked. So, I collated them under the heading Vineyard Sightings.

Two of my favorite vineyard sightings are
(1)Seeing a murmuration of starlings one fall morning:
Birds: Director's Cut
(2)A flock of around 30-40 turkeys in a race with my husband on a tractor:
Turkeys vs. Tractor

2013 Javillier Savigny-Les-Beaune Premier Cru Les Serpentieres Bourgogne

We had one of our friends over for a mid-week dinner of duck with berry sauce and a side dish of roasted mushrooms with chickpeas, tomatoes and rosemary. The duck with berry sauce is one of our goto meals. It is easy to make and turns out delicious.
My husband reminded me that we had this 2013 Javillier Savigny-Les-Beaune Premier Cru Les Serpentieres Bourgogne with lamb, where it didn't quite stand up to the rich meatiness of the lamb.
On this night, we paired the wine with duck. This is a light to medium bodied Pinot noir that was a clear, sparkling purple in the glass with notes of red cherries and raspberries. The berry notes in the wine was a perfect echo of the berry sauce and it paired very well. It wasn't an overly fruity wine and has a mineral finish.
As I write this, we are watching not quite whiteout snowfall in southeastern Connecticut. Mother Nature seems to be sending her annual Valentine's Day blizzard a few days early.

Vintage 2017: Winter

I'm continuing with blogging about Vintage Notes as a way to remind myself what kind of conditions we were looking at during the growing season. I thought I had winter figured out, having lived here for more than 30 years. January can get quite cold with temperatures that can be below freezing but during the second or third week in January, there is generally a thaw. After January, temperatures still can be cold, but the worst of it is over. Not!
Beginning in the winter of 2013-2014, when we had new vines in the ground, we experienced what the weather forecasters were calling a polar vortex. We had so much snow in 2014 and ditto in 2015. However, in 2016, we had a very mild winter which boded well for us because we were on the hook to drill 4200 holes for our new plants.
If you believe Punxsutawney Phil, we are in for 6 more weeks of winter. I can vouch that February 14th, Valentine's Day will be the worse snowfall in the northeast because that is what the forecasters have said for the last three years. I would say that 2 out of 3 times, they did get it right. Here is what I located for the month of January in 2016 compared to 2017:

The general trend does appear to be a cold dip during the first part of January followed by a slight warmup during the latter part of the month. Although we have not had much snow, we have had a good share of rain, which is different from last year. I retrieved the above information from here: AccuWeather.com.

New Tab Called "Chenin Blanc"

Since we are growing and making wine from one of our favorite white grapes, Chenin Blanc, I thought that it would be appropriate to have a tab dedicated to Chenin Blanc.

The following blogposts are collated under the newly created Chenin Blanc tab:
Visit with Charles Massoud at Paumanok Winery
Chenin Blanc---the Rodney Dangerfield of White Wines
2009 Laurent Kraft Vouvray
2009 Petit Chenin
2010 Domaine Huet Clos du Bourg
2010 Paumanok Chenin Blanc
2004 Baumard Savennieres
2010 Chinon Les Chanteaux Couly-Dutheil
2012 Clos le Vigneau Vouvray
Sad Day: Noël Pinguet is Leaving Domaine Huët
Ken Forrester Visit
2012 Clos le Vigneau Vouvray
2010 Richard Leroy Noëls de Montbenault Chenin Blanc
2014 Waitsburg Cellars Cheninières
2013 Terres Blanches Saumur
2014 Paumanok Minimalist Chenin Blanc
2010 Domaine Huet Le Mont
2013 Millton Chenin Blanc
2012 Anjou Blanc
2014 Chateau D'Epire Savennières
2013 Guiberteau Samur
2014 Domaine Guiberteau Les Moulins

The Concept of Berry Sugar Loading

We heard from a few of our friends who farm grapes that in this past year, 2016, they saw their sugar accumulation plateau at a low sugar level when it neared harvest time. I was rereading some of my previous blogposts in an effort to do a better job of categorizing all the previous posts and came across a blog that I had written in September 2013 called: Predicting Harvest Date.
In that post, I wrote about the concept of berry sugar loading which occurs after véraison, the onset of fruit maturation.
Berry sugar loading leads to berry softening as sucrose is being transported to the berry and hydrolyzed into it's components, glucose and fructose. This allows glucose and fructose to be accumulated in the berry, creating a concentration gradient.
According to the article written by Alain Deloire of Charles Sturt University, Bathurst, it is possible to distinguish three principal sugar loading profiles:
     1. Continual and rapid loading is considered to be beneficial for the production of rosé, fresh fruit red wines, or pleasant aromatic white wines.
     2. Slow sugar loading – inhibition of ripening is considered to be a form of “blocked” ripening and this could be indicative of major physiological problems, such as mineral deficiencies, viral diseases etc., as well as excessive water deficit or to an excessive crop load in relation to the exposed leaf surface.
     3. Sugar loading presenting a plateau phase vines showing this tendency present a phase of active sugar loading in the berry (ripening), followed by a plateau representing a cessation of sugar loading corresponding to maturity.
The concept can be visualized in the following figure.

The take home message for me from reading this article is that a continual and rapid loading of sugar to achieve the desired level of Brix can be disrupted by disease states which include excessive water deficit, which some farmers in our area experienced last harvest.
Reference:
1. Alain Deloire, The concept of berry sugar loading, January 6, 2016.