National Key Laboratory for Germplasm Innovation and Utilization of Horticultural Crops, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, 430070, Hubei, China.
Plant Physiol Biochem. 2023 Oct;203:108056. doi: 10.1016/j.plaphy.2023.108056. Epub 2023 Sep 23.
To investigate the mechanism for drought promoting soluble sugar accumulation will be conducive to the enhancement of citrus fruit quality as well as stress tolerance. Fruit sucrose mainly derives from source leaves. Its accumulation in citrus fruit cell vacuole involves in two processes of unloading in the fruit segment membrane (SM) and translocating to the vacuole of fruit juice sacs (JS). Here, transcript levels of 47 sugar metabolism- and transport-related genes were compared in fruit SM or JS between drought and control treatments. Results indicated that transcript levels of cell wall invertase genes (CwINV2/6) and sucrose synthase genes (SUS2/6) in the SM were significantly increased by the drought. Moreover, transcript levels of SWEET genes (CsSWEET1/2/4/5/9) and monosaccharide transporter gene (CsPMT3) were significantly increased in SM under drought treatment. On the other hand, SUS1/3 and vacuolar invertase (VINV) transcript levels were significantly increased in JS by drought; CsPMT4, sucrose transporter gene 2 (CsSUT2), tonoplast monosaccharide transporter gene 2 (CsTMT2), sugar transport protein gene 1 (CsSTP1), two citrus type I V-PPase genes (CsVPP1, and CsVPP2) were also significantly increased in drought treated JS. Collectively, the imposition of drought stress resulted in more soluble sugar accumulation through enhancing sucrose download by enhancing sink strength- and transport ability-related genes, such as CwINV2/6, SUS2/6, CsSWEET1/2/4/5/9, and CsPMT3, in fruit SM, and soluble sugar storage ability by increasing transcript levels of genes, such as CsPMT4, VINV, CsSUT2, CsTMT2, CsSTP1, CsVPP1, and CsVPP2, in fruit JS.
为了研究干旱促进可溶性糖积累的机制，这将有助于提高柑橘果实的品质和增强其对胁迫的耐受性。果实中的蔗糖主要来源于源叶。其在柑橘果实细胞液泡中的积累涉及两个过程：在果实段膜（SM）中卸载以及转运到果汁囊（JS）的液泡中。在这里，比较了干旱和对照处理下果实 SM 或 JS 中 47 个与糖代谢和运输相关的基因的转录水平。结果表明，SM 中细胞壁转化酶基因（CwINV2/6）和蔗糖合酶基因（SUS2/6）的转录水平因干旱而显著增加。此外，干旱处理下 SM 中 SWEET 基因（CsSWEET1/2/4/5/9）和单糖转运蛋白基因（CsPMT3）的转录水平显著增加。另一方面，SUS1/3 和液泡转化酶（VINV）的转录水平在 JS 中因干旱而显著增加；CsPMT4、蔗糖转运蛋白基因 2（CsSUT2）、液泡膜单糖转运蛋白基因 2（CsTMT2）、糖转运蛋白基因 1（CsSTP1）、两种柑橘型 I V-PPase 基因（CsVPP1 和 CsVPP2）在干旱处理的 JS 中也显著增加。总之，通过增强与蔗糖下载相关的基因，如 CwINV2/6、SUS2/6、CsSWEET1/2/4/5/9 和 CsPMT3，增强果实 SM 中的库强度和运输能力，以及通过增加基因的转录水平来增强果实 JS 中的可溶性糖储存能力，如 CsPMT4、VINV、CsSUT2、CsTMT2、CsSTP1、CsVPP1 和 CsVPP2，干旱胁迫导致更多的可溶性糖积累。
