In higher plants, the development of the vascular system is controlled by a complex network of transcription factors. However, how nutrient availability in the vascular cells affects their development remains to be addressed. At the cellular level, cytosolic sugar availability is regulated mainly by sugar exchanges at the tonoplast through active and/or facilitated transport. In Arabidopsis thaliana, among the tonoplastic transporters, SWEET16 and SWEET17 genes have been previously localized in the vascular system. Here, using a reverse genetic approach, we propose that sugar exchanges at the tonoplast, regulated by SWEET16, are important for xylem cell division as revealed in particular by the decreased number of xylem cells in the swt16 mutant and the expression of SWEET16 at the procambium-xylem boundary. In addition, we demonstrate that transport of hexoses mediated by SWEET16 and/or SWEET17 is required to sustain the formation of the xylem secondary cell wall. This result is in line with a defect in the xylem cell wall composition as measured by FTIR in the swt16swt17 double mutant and by upregulation of several genes involved in secondary cell wall synthesis. Our work therefore supports a model in which xylem development is partially dependent on the exchange of hexoses at the tonoplast of xylem-forming cells.

中文翻译：

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拟南芥花序茎的木质部发育需要液泡己糖转运

在高等植物中，维管系统的发育由复杂的转录因子网络控制。然而，血管细胞中的营养可用性如何影响它们的发育仍有待解决。在细胞水平上，细胞溶质糖的可用性主要由液泡膜处的糖交换通过主动和/或促进运输来调节。在拟南芥中，在张力性转运蛋白中，SWEET16和SWEET17基因先前已定位于血管系统中。在这里，使用反向遗传方法，我们提出由 SWEET16 调节的液泡膜处的糖交换对于木质部细胞分裂很重要，特别是通过swt16中木质部细胞数量的减少所揭示的突变体和 SWEET16 在原形成 - 木质部边界的表达。此外，我们证明了由 SWEET16 和/或 SWEET17 介导的己糖运输是维持木质部次生细胞壁形成所必需的。该结果与木质部细胞壁组成的缺陷一致，如通过swt16swt17双突变体中的 FTIR以及参与次生细胞壁合成的几个基因的上调所测量的。因此，我们的工作支持一种模型，其中木质部发育部分依赖于形成木质部的细胞液泡中的己糖交换。