Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables/Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (South China), Ministry of Agriculture and Rural Affairs, College of Horticulture, South China Agricultural University, Guangzhou 510642, China.
Int J Mol Sci. 2023 Aug 17;24(16):12882. doi: 10.3390/ijms241612882.
The sugar composition and content of fruit have a significant impact on their flavor and taste. In pitaya, or dragon fruit, sweetness is a crucial determinant of fruit taste and consumer preference. The sugars will eventually be exported transporters (SWEETs), a novel group of sugar transporters that have various physiological functions, including phloem loading, seed filling, nectar secretion, and fruit development. However, the role of SWEETs in sugar accumulation in pitaya fruit is not yet clear. Here, we identified 19 potential members ( genes) of the family in pitaya and analyzed their conserved motifs, physiochemical characteristics, chromosomal distribution, gene structure, and phylogenetic relationship. Seven highly conserved α-helical transmembrane domains (7-TMs) were found, and the HuSWEET proteins can be divided into three clades based on the phylogenetic analysis. Interestingly, we found two genes, and , that showed strong preferential expressions in fruits and an upward trend during fruit maturation, suggesting they have key roles in sugar accumulation in pitaya. This can be further roughly demonstrated by the fact that transgenic tomato plants overexpressing / accumulated high levels of sugar in the mature fruit. Together, our result provides new insights into the regulation of sugar accumulation by family genes in pitaya fruit, which also set a crucial basis for the further functional study of the
火龙果的糖组成和含量对其风味和口感有重大影响。在火龙果中，甜度是决定果实口感和消费者喜好的关键因素。糖最终会被输出载体（SWEETs）运出，这是一类具有多种生理功能的新型糖转运蛋白，包括韧皮部装载、种子填充、花蜜分泌和果实发育。然而，SWEETs 在火龙果果实糖积累中的作用尚不清楚。在这里，我们在火龙果中鉴定了 19 个 SWEET 家族的潜在成员（基因），并分析了它们的保守基序、理化特性、染色体分布、基因结构和系统发育关系。发现了七个高度保守的α-螺旋跨膜结构域（7-TMs），根据系统发育分析，HuSWEET 蛋白可分为三个分支。有趣的是，我们发现两个基因 和 在果实中表现出强烈的优先表达，并在果实成熟过程中呈上升趋势，表明它们在火龙果糖积累中具有关键作用。这可以通过转番茄植物过表达 / 在成熟果实中积累高水平糖这一事实得到进一步证实。总之，我们的结果为火龙果果实中 SWEET 家族基因调控糖积累提供了新的见解，也为进一步研究 SWEET 家族基因的功能奠定了关键基础。
