Effect of Trunk Girdling on Anthocyanin Accumulation and Expression Levels of Anthocyanin Biosynthesis-related Genes in ‘Aki-queen’ Grapes

Abstract

We investigated the effect of trunk girdling on the skin color and expression levels of anthocyanin biosynthesis-related genes in the red grape ‘Aki Queen’ (Vitis labrusca L. × V. vinifera L.). Trunk girdling at the onset of coloring in mid-July significantly accelerated anthocyanin accumulation in the berry skin during maturation in comparison with that in the control (no girdling). Using quantitative real-time PCR analysis, we showed that the expression levels of anthocyanin biosynthesis-related genes such as chalcone synthase 3 (CHS3), UDP-glucose: flavonoid 3-O-glucosyltransferase (UFGT), and anthocyanin O-methyltransferase (AOMT) were significantly increased by trunk girdling in comparison with the control, although the expression levels of CHS3, UFGT, and AOMT gradually increased from mid-July to early August in both the girdling treatment and control. The anthocyanin content was closely correlated with the expression levels of many anthocyanin biosynthesis-related genes. These findings suggest that trunk girdling at the onset of coloring improves the skin color of ‘Aki Queen’ grapes by accelerating the expression of anthocyanin biosynthesis-related genes. ブドウ‘安芸クイーン’への環状はく皮処理が，果皮色ならびにアントシアニン合成関連遺伝子群の発現量に及ぼす影響を調査した．着色開始期（満開35 日後）における主枝への環状はく皮処理により，果皮色が対照（無処理）区と比較して著しく向上した．また，環状はく皮処理により，主に7 月中下旬～ 8 月上旬におけるアントシアニン合成関連遺伝子群の発現量が対照区と比較して有意に増加し，成熟期間を通した累積発現量も増加した．また，アントシアニン含量と多くのアントシアニン合成関連遺伝子群の累積発現量との間に正の相関が認められた．以上のとおり，環状はく皮処理によって成熟期における果皮のアントシアニン合成関連遺伝子群の累積発現量が増加し，これによりアントシアニン合成が促進することが明らかとなった．また，多くの関連遺伝子の発現量が増加しはじめる着色開始期の環状はく皮処理が‘安芸クイーン’の着色向上に有効であることが示された．