The Accumulation Of Flavanols, Expression Of Leucoanthocyanidin Reductase Induced By UV-C Irradiation In Grape Berry

Flavanols, which are synthesized by the phenylpropanoid and flavonoid pathways, are one subclass of the polyphenols and widely distributed in plants. it is not only involved in growth and development of plants, but also provided resistance against ultraviolet rays, pest, ion toxicity and other harms for plants. Meanwhile, flavanols have a important role in the sensory quality of the wine, such as flavor, color, clarity, convergence and browning, etc. Leucoanthocyanidin Reductase (LAR), an (+)-Catechin synthetic precursor enzyme, acts as the key enzyme in flavanols biosynthesis. In this study, the plants of the5-years old grape(Vitis vinifera L. cv. Cabernet Sauvignon) at the distinctive development stages and the mature fruits after harvest were treated with UV-C irradiation, and the influences of the UV-C irradiation on the quality formation and polyphenols, especially for flavanols accumulation and the expression of lor in the grape berry during the development, the enzyme activity and protein expression of the (+)-Catechin synthetic precursor enzyme-the LAR were investigated. The main results were as follows:1. Fruit quality was influenced obviously by the moderate UV-C irradiation. The pattern of fruit quality formation was not changed, while the fruit quality was changed significantly with the regular UV-C irradiation. No obvious change in single berry weight and content of organic acid was observed, while the accumulation of anthocyanins and the total sugar were increased, the Vc was decreased. In addition, the effect of UV-C on the fruit quality formation was development-and dose-depended.2. The pattern of the flavanols accumulation in grape berry was not changed, while the flavanols accumulation was improved by UV-C, especially in the young berry. The pattern of LAR activity during grape berry development was not changed, while the LAR activity was up-regulated significantly with UV-C irradiation. The results of western-blot showed that the protein expression levels of LAR1and LAR2were higher than CK. The results of Real time PCR showed that the expression levels of Vvlar1and Vvlar2were up-regulated by UV-C irradiation.3. The content of the flavanols was increased with the increased irradiation time, while enzyme activity of the LAR showed a trend of first increasing and then reducing. The results of western-blot showed that the protein expression levels of LAR1increased firstly and then decreased, however, LAR2tended to drop off with the increased irradiation time. The results of Real time PCR showed that the expression levels of Vvlar1and Vvlar2increased firstly and then decreased with the increased irradiation time, and the expression level of Vvlar1was significantly lower than Vvlar2.