Study On The Mechanism Of Improved Anthocyanin Biosynthesis Under Root Restriction In Table Grape Berry Skin

Anthocyanin content and composition determine the color profile of table grapesand influence their sensory quality, and nutritional and commercial values. Rootrestriction was reported to improve grape coloration and increase the total content ofanthocyanin in berry grape skin. However, it remained unclear how the rootrestriction may affect the individual anthocyanin composition, the modification ofanthocyanins and the expression of genes important for anthocyanin biosynthesis. Inthis study, hybrids of Vitis vinifera and Vitis labrusca, Kyoho‘and Summer Black‘were employed to investigate the effect of root restriction on anthocyanin biosynthesisand color development. Grapevines planted in the normal open ground were set as thecontrol. The anthocyanin compositions during berry development were examinedusing a HPLC/MSD-ESI-MS method. Meanwhile, different anthocyanin modificationtypes were analyzed. The expression patterns of fifteen structural genes and fourregulatory genes in anthocyanin biosynthesis pathway were analyzed through RT-PCR.Results were as following:1. For both Kyoho‘and Summer Black‘grape, the growth of grapevine wasinhibited, while the growth of fruits was enhanced since veraison under rootrestriction. Root restriction improved the fruit quality by increasing the content oftotal soluble solids, pH value and TSS/TA. The content of fructose, glucose and totalsugar content were also increased by root restriction.2. The onset of anthocyanin biosynthesis was earlier under root restriction.Besides, the total content and the amount of individual anthocyanins were increasedby root restriction during berry development. Meanwhile, there were moreanthocyanins detected in fruits with root restriction treatment. Twenty-five anthocyanins were detected in kyoho‘grape grown in Shanghai under rootrestriction with six anthocyanins more than that in the control. There were29anthocyanins detected in Summer Black‘grape grown in Nanning under rootrestriction, whereas only27anthocyanins detected in the control.3. Changes in the content and level of individual anthocyanin modificationwere altered by root restriction. The content of all types of modified anthocyaninswere increased by root restriction, but the level of changes might differ to eachother. Under root restriction,3‘5‘-substitude derivatives increased more than3‘-substitude derivatives, meanwhile the proportion of3‘5‘-substitude derivativeswas greater in the fruits grown under root restriction at harvest；Methoxylatedderivatives increased more than non-methoxylated derivatives, however the ratioof methoxylated derivatives was decreased by root restriction at harvest; Rootrestriction differentially influenced the acylated anthocyanin modification in kyoho‘and Summer Black‘grapes. Root restrction increased different acylatedanthocyanins in Kyoho‘grape at different level: coumaroylated derivatives＞non-acylated derivatives＞acetylated derivatives, while in Summer Black‘grape:non-acylated derivatives＞coumaroylated derivatives＞acetylated derivatives. Interms of the proportion changes of different acylated anthocyanins caused by rootrestriction: the proportion of coumaroylated derivatives was increased while theproportion of non-acylated derivatives and acetylated was decreased by rootrestriction in Kyoho‘grape; the proportion of non-acylated derivatives wasincreased while the proportion of coumaroylated derivatives and acetylatedderivatives was decreased by root restriction in Summer Black‘grape.4. The transcriptional expression of structural genes PAL、4CL、CHS2、CHS3、CHI1、F3Hs、DFR、LDOX and regulatory genes VlmybA1-1、VvmybA1inanthocyanin biosynthesis pathway were up-regulated by root restriction in both Kyoho‘and Summer Black‘grapes (during the whole or part of berrydevelopment stages). The up-regulation of these genes by root restriction wasrelated to the increase of anthocyanin biosynthesis. Root restriction up-regulatedthe expression of F3’H and F3’5’H, and dramatically F3’5’H. The expression of 3GT was up-regulated by root restriction throughout the fruit development stages. Thetranscriptional level of5GT was higher under root restriction treatment in Kyoho‘forall sampling dates and in Summer Black‘in part of sampling dates. The up-regulationof OMT by root restriction was after veraison in Kyoho‘but was before veraison in Summer Black‘grapes. The different regulation pattern of these genes was related toboth the total anthocyanins and the level of corresponding modified anthocyanins.