INRAE, UR1115, Unité Plantes et Systèmes de Culture Horticoles, Avignon, France.
Université Côte d'Azur, INRAE, CNRS, Institut Sophia Agrobiotech, Sophia-Antipolis, France.
Ann Bot. 2020 Aug 13;126(3):455-470. doi: 10.1093/aob/mcaa082.
Sugar concentration is a key determinant of fruit quality. Soluble sugars and starch concentrations in fruits vary greatly from one species to another. The aim of this study was to investigate similarities and differences in sugar accumulation strategies across ten contrasting fruit species using a modelling approach.
We developed a coarse-grained model of primary metabolism based on the description of the main metabolic and hydraulic processes (synthesis of compounds other than sugar and starch, synthesis and hydrolysis of starch, and water dilution) involved in the accumulation of soluble sugars during fruit development.
Statistical analyses based on metabolic rates separated the species into six groups according to the rate of synthesis of compounds other than sugar and starch. Herbaceous species (cucumber, tomato, eggplant, pepper and strawberry) were characterized by a higher synthesis rate than woody species (apple, nectarine, clementine, grape and kiwifruit). Inspection of the dynamics of the processes involved in sugar accumulation revealed that net sugar importation, metabolism and dilution processes were remarkably synchronous in most herbaceous plants, whereas in kiwifruit, apple and nectarine, processes related to starch metabolism were temporally separated from other processes. Strawberry, clementine and grape showed a distinct dynamic compared with all other species.
Overall, these results provide fresh insights into species-specific regulatory strategies and into the role of starch metabolism in the accumulation of soluble sugars in fleshy fruits. In particular, inter-specific differences in development period shape the co-ordination of metabolic processes and affect priorities for carbon allocation across species. The six metabolic groups identified by our analysis do not show a clear separation into climacteric and non-climacteric species, possibly suggesting that the metabolic processes related to sugar concentration are not greatly affected by ethylene-associated events.
糖浓度是果实品质的关键决定因素。不同物种之间果实的可溶性糖和淀粉浓度差异很大。本研究旨在通过建模方法研究十种不同果实中糖积累策略的异同。
我们基于参与果实发育过程中可溶性糖积累的主要代谢和水力过程（除糖和淀粉以外的化合物的合成、淀粉的合成和水解以及水稀释）的描述，开发了一种基于粗粒度模型的初级代谢模型。
基于代谢率的统计分析将物种分为六组，根据除糖和淀粉以外的化合物的合成速率进行分类。草本物种（黄瓜、番茄、茄子、辣椒和草莓）的合成速率高于木本物种（苹果、油桃、克莱门氏小柑橘、葡萄和猕猴桃）。对参与糖积累的过程动态的检查表明，在大多数草本植物中，净糖输入、代谢和稀释过程非常同步，而在猕猴桃、苹果和油桃中，与淀粉代谢有关的过程在时间上与其他过程分离。草莓、克莱门氏小柑橘和葡萄与所有其他物种表现出明显的动态差异。
总的来说，这些结果为特定物种的调节策略以及淀粉代谢在肉质果实中可溶性糖积累中的作用提供了新的见解。特别是，不同物种的发育时期差异塑造了代谢过程的协调，并影响了跨物种的碳分配优先级。我们的分析确定的六个代谢组在是否为呼吸跃变型和非呼吸跃变型物种之间没有明显的分离，这可能表明与糖浓度相关的代谢过程不受乙烯相关事件的影响。
