Sorbitol is the primary substrate translocated from source to sink in pear species. Among the many sorbitol transporters (SOTs), some are known to be involved in sorbitol accumulation in fruit; however, their particular roles are unclear. In this study, we examined the transcriptome and metabolome of a variety of pear samples from six time points to identify those SOTs. Similar to previous studies, sorbitol and sucrose differed significantly between the leaf and fruit, and sorbitol was consistently observed at higher concentrations at all time points. Interestingly, we found that sorbitol accumulation in pear fruit was cooperatively mediated by SOT3, SOT6/20, SOT19/21, and SOT22. In particular, the up-regulated SOT6/20 and SOT19/21 in fruit under 1 mg L-1 abscisic acid and 10 mg L-1 indole acetic acid treatments, respectively, resulted in an increased sorbitol concentration. In addition, sorbitol concentration showed positive correlations to fructose and glucose concentrations, indicating a role for sorbitol in the determination of fruit sweetness. Together with the deduced process of sugar biosynthesis, transport, conversion, and accumulation in pear, our study provides a foundation for further research into sugar accumulation processes in pear fruit, contributing to the improvement of fruit quality.

中文翻译：

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时空表达的山梨糖醇转运蛋白协同调控梨果实中山梨糖醇的积累

山梨糖醇是梨物种中从源转移到汇的主要底物。在众多山梨糖醇转运蛋白 (SOT) 中，一些已知参与水果中山梨糖醇的积累；然而，它们的具体作用尚不清楚。在这项研究中，我们检查了来自六个时间点的各种梨样品的转录组和代谢组，以识别这些 SOT。与之前的研究类似，山梨糖醇和蔗糖在叶子和果实之间存在显着差异，并且在所有时间点都始终以较高浓度观察到山梨糖醇。有趣的是，我们发现梨果实中山梨糖醇的积累是由 SOT3、SOT6/20、SOT19/21 和 SOT22 共同介导的。特别是，分别在 1 mg L-1 脱落酸和 10 mg L-1 吲哚乙酸处理下上调果实中的 SOT6/20 和 SOT19/21，导致山梨糖醇浓度增加。此外，山梨糖醇浓度与果糖和葡萄糖浓度呈正相关，表明山梨糖醇在水果甜度测定中的作用。结合梨中糖的生物合成、运输、转化和积累过程的推导，我们的研究为进一步研究梨果实中糖的积累过程提供了基础，有助于提高果实品质。