State Key Laboratory of Crop Stress Biology for Arid Areas, Key Laboratory of Genetic Improvement of Horticultural Crops of Northwest China, College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, P.R. China; and Department of Viticulture and Enology, University of California, Davis, 95616-3014.
State Key Laboratory of Crop Stress Biology for Arid Areas, Key Laboratory of Genetic Improvement of Horticultural Crops of Northwest China, College of Horticulture, Northwest A&F University, Yangling 712100, Shaanxi, P.R. China.
Plant Dis. 2017 Sep;101(9):1606-1615. doi: 10.1094/PDIS-01-17-0104-RE. Epub 2017 Jul 10.
Reddish-purple coloration on the leaf blades and downward rolling of leaf margins are typical symptoms of grapevine leafroll disease (GLD) in red-fruited grapevine cultivars. These typical symptoms are attributed to the expression of genes encoding enzymes for anthocyanins synthesis, and the accumulation of flavonoids in diseased leaves. Drought has been proven to accelerate development of GLD symptoms in virus-infected leaves of grapevine. However, it is not known how drought affects GLD expression nor how anthocyanin biosynthesis in virus-infected leaves is altered. The present study used HPLC to determine the types and levels of anthocyanins, and applied reverse transcription quantitative polymerase chain reaction (RT-qPCR) to analyze the expression of genes encoding enzymes for anthocyanin synthesis. Plantlets of Grapevine leafroll-associated virus 3 (GLRaV-3)-infected Vitis vinifera 'Cabernet Sauvignon' were grown in vitro under PEG-induced drought stress. HPLC found no anthocyanin-related peaks in the healthy plantlets with or without PEG-induced stress, while 11 peaks were detected in the infected plantlets with or without PEG-induced drought stress, but the peaks were significantly higher in infected drought-stressed plantlets. Increased accumulation of total anthocyanin compounds was related to the development of GLD symptoms in the infected plantlets under PEG stress. The highest level of up-regulated gene expression was found in GLRaV-3-infected leaves with PEG-induced drought stress. Analyses of variance and correlation of anthocyanin accumulation with related gene expression levels found that GLRaV-3-infection was the key factor in increased anthocyanin accumulation. This accumulation involved the up-regulation of two key genes, MYBA1 and UFGT, and their expression levels were further enhanced by drought stress.
叶片呈紫红色和叶缘向下卷曲是葡萄卷叶病（GLD）在红色果实葡萄品种中的典型症状。这些典型症状归因于编码花色素苷合成酶的基因表达和患病叶片中类黄酮的积累。干旱已被证明会加速感染病毒的葡萄叶片中 GLD 症状的发展。然而，尚不清楚干旱如何影响 GLD 表达，也不知道感染病毒的叶片中花色素苷生物合成如何发生改变。本研究使用高效液相色谱法（HPLC）测定花色素苷的类型和水平，并应用反转录定量聚合酶链反应（RT-qPCR）分析编码花色素苷合成酶的基因表达。采用 PEG 诱导干旱胁迫，在体外培养感染葡萄卷叶伴随病毒 3（GLRaV-3）的酿酒葡萄‘赤霞珠’幼苗。HPLC 发现健康的幼苗无论是否受到 PEG 诱导的胁迫，均未检测到与花色素苷相关的峰，而感染的幼苗无论是否受到 PEG 诱导的干旱胁迫，均检测到 11 个峰，但在感染干旱胁迫的幼苗中，这些峰显著更高。总花色素苷化合物的积累与感染植株在 PEG 胁迫下 GLD 症状的发展有关。在感染 GLRaV-3 的叶片中，PEG 诱导干旱胁迫下基因表达上调幅度最大。方差分析和花色素苷积累与相关基因表达水平的相关性分析发现，GLRaV-3 感染是增加花色素苷积累的关键因素。这种积累涉及到两个关键基因 MYBA1 和 UFGT 的上调，并且它们的表达水平进一步受到干旱胁迫的增强。
