National Watermelon and Melon Improvement Center, Beijing Academy of Agricultural and Forestry Sciences (BAAFS), State Key Laboratory of Vegetable Biobreeding, Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (North China), Beijing Key Laboratory of Vegetable Germplasm Improvement, Beijing 100097, China.
Plant Physiol. 2023 Sep 22;193(2):888-899. doi: 10.1093/plphys/kiad294.
Fruit sweetness is determined by the amount and composition of sugars in the edible flesh. The accumulation of sugar is a highly orchestrated process that requires coordination of numerous metabolic enzymes and sugar transporters. This coordination enables partitioning and long-distance translocation of photoassimilates from source tissues to sink organs. In fruit crops, sugars ultimately accumulate in the sink fruit. Whereas tremendous progress has been achieved in understanding the function of individual genes associated with sugar metabolism and sugar transport in non-fruit crops, there is less known about the sugar transporters and metabolic enzymes responsible for sugar accumulation in fruit crop species. This review identifies knowledge gaps and can serve as a foundation for future studies, with comprehensive updates focusing on (1) the physiological roles of the metabolic enzymes and sugar transporters responsible for sugar allocation and partitioning and that contribute to sugar accumulation in fruit crops; and (2) the molecular mechanisms underlying the transcriptional and posttranslational regulation of sugar transport and metabolism. We also provide insights into the challenges and future directions of studies on sugar transporters and metabolic enzymes and name several promising genes that should be targeted with gene editing in the pursuit of optimized sugar allocation and partitioning to enhance sugar accumulation in fruits.
水果的甜度取决于可食用果肉中糖的含量和组成。糖的积累是一个高度协调的过程，需要协调许多代谢酶和糖转运蛋白。这种协调使来自源组织的光合同化物能够进行分区和长距离转运到汇器官。在水果作物中，糖最终积累在汇器官中。尽管在非水果作物中，与糖代谢和糖转运相关的单个基因的功能已经取得了巨大进展，但对于负责糖积累的水果作物中的糖转运蛋白和代谢酶知之甚少。本综述确定了知识空白，并可以作为未来研究的基础，全面更新重点关注：（1）负责糖分配和分区并有助于水果作物中糖积累的代谢酶和糖转运蛋白的生理作用；（2）糖转运和代谢的转录后和翻译后调控的分子机制。我们还深入了解了糖转运蛋白和代谢酶研究的挑战和未来方向，并提出了一些有前途的基因，这些基因应该通过基因编辑进行靶向，以优化糖的分配和分区，从而提高水果中的糖积累。
