|Cohen, Seth -|
|Gambetta, Gregory -|
|Matthews, Mark -|
|Kennedy, James -|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 31, 2012
Publication Date: May 7, 2012
Citation: Cohen, S., Tarara, J.M., Gambetta, G., Matthews, M., Kennedy, J. 2012. Impact of diurnal temperature variation on grape berry development, proanthocyanidin accumulation, and the expression of flavonoid pathway genes. Journal of Experimental Botany. 63:2655-2665. Interpretive Summary: Various chemical components of wines are influenced heavily by growing conditions in the vineyard. These changes are mediated by the end products encoded by a number of grapevine genes. We manipulated the temperature of grape clusters at different times during their development to determine how one large class of natural chemical compounds, the tannins, develop. In addition, we determined whether the genes responsible for tannin production differed in the extent to which they were 'turned on' as a result of the different temperatures. The temperatures applied reflected a few of the potential temperature scenarios associated with global climate change models. Although grape temperatures were changed by more than 10 degrees, the genes responsible for tannin production did not change the extent to which they were turned 'on.' However, the genes associated with the dark color seen in the skins of grapes did change their degree of being turned 'on.'
Technical Abstract: Little is known about the impact of temperature on proanthocyanidin (PA) accumulation in grape skins, despite its significance in berry composition and wine quality. Field grown grapes (cv. Merlot) were cooled during the day or heated at night by +/- 8 °C, from fruit set to véraison in three seasons, to determine the effect of temperature on PA accumulation. Total PA content per berry varied only in one year, when PA content was highest in heated berries (1.46 mg · berry-1) and lowest in cooled berries (0.97 mg · berry-1). In two years, cooling berries resulted in a significant increase in the proportion of (-)-epigallocatechin as an extension subunit. In the third year, rates of berry development, PA accumulation, and the expression levels of several genes involved in flavonoid biosynthesis were assessed. Heating and cooling berries altered initial rates of PA accumulation, which was correlated strongly with the expression of core genes in the flavonoid pathway. Both heating and cooling altered the rate of berry growth and coloration and the expression of several structural genes within the flavonoid pathway.