Enzyme activities and gene expression of starch metabolism provide insights into grape berry development. (10th May 2017)

• Record Type: Journal Article
• Authors: Zhu, Xudong; Zhang, Chaobo; Wu, Weimin; Li, Xiaopeng; Zhang, Chuan; Fang, Jinggui
• Is Part Of: Horticulture research. Volume 4(2017)
• Publication Date: 2017-05-10
• Subjects: Metabolism -- Non-model organisms -- Plant molecular biology; Horticulture -- Research -- Periodicals; 635.072
• DOI: 10.1038/hortres.2017.18
• Languages: English
• ISSNs: 2052-7276

Abstract

Abstract: Grapes are categorized as a non-climacteric type of fruit which its ripening is not associated to important rises in respiration and ethylene synthesis. The starch metabolism shares a certain role in the carbohydrate metabolic pathways during grape berry development, and is regarded as an important transient pool in the pathway of sugar accumulation. However, the comprehensive role of starch and its contribution to the quality and flavor of grape berry have not been explored thoroughly. In this study, the expression levels of genes enzyme activities and carbohydrate concentrations related to starch metabolism, were analyzed to understand the molecular mechanism of starch accumulation during grape berry development. The results indicated that starch granules in grape berry were located at the chloroplast in the sub-epidermal tissues, acting as the temporary reserves of photosynthetic products to meet the needs for berry development, and relatively high starch contents could be detected at véraison stage. Moreover, both ADP-glucose pyrophosphorylase (EC 2.7.7.27) and sucrose phosphate synthase (EC 2.3.1.14) involved in starch synthesis displayed elevated gene expression and enzymes activities in the sub-epidermal tissue, while α- and β-amylases involved in its degradation were highly transcribed and active in the central flesh, explaining the absence of starch in this last tissue. Change in the gene expression and activities of ADP-glucose pyrophosphorylase, β-amylase and sucrose phosphate synthase revealed that they were regulated by the circadian rhythms in the fruitlets compared with those in the leaves. Both the morphological, enzymological and transcriptional data in this study provide advanced understandings on the function of starch during berry development and ripening that are so important for berry quality. This study will further facilitate our understanding of the sugar metabolism in grape berry as well as in other plant species. Abstract : Fruit quality: Carbohydrates help grapes make the grade The creation and degradation of carbohydrates such as starch and sugars during grape ripening have important implications for fruit quality. Growers and consumers are increasingly seeking out grapes with greater sugar content, a characteristic which is controlled by the genes and enzymes of starch metabolism. Jinggui Fang of Nanjing Agricultural University, China, and colleagues explored the expression of genes and activity of enzymes causing starch synthesis and breakdown in a red grape cultivar using multiple experimental techniques. They conclude that starch metabolism is a complex, dynamic process, with different genes active in different parts of the grape fruit. Remarkably, changes in starch concentration in fruits were found to be regulated by circadian rhythmns in a similar way to those in leaves. Their findings should help breeders optimise grape varieties for future fruit quality.