Institut Jean-Pierre Bourgin, INRAE, AgroParisTech, Université Paris-Saclay, 78000 Versailles, France.
Ecole Doctorale 567 Sciences du Végétal, Univ Paris-Sud, Univ Paris-Saclay, bat 360, 91405 Orsay Cedex, France.
Plant Physiol. 2022 Feb 4;188(2):1229-1247. doi: 10.1093/plphys/kiab551.
In Angiosperms, 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 (Arabidopsis thaliana), among the genes encoding tonoplastic transporters, SUGAR WILL EVENTUALLY BE EXPORTED TRANSPORTER 16 (SWEET16) and SWEET17 expression has been previously detected in the vascular system. Here, using a reverse genetics 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 accumulation 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 Fourier-transformed infrared spectroscopy 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 partially depends on the exchange of hexoses at the tonoplast of xylem-forming cells.
在被子植物中，血管系统的发育受转录因子复杂网络的控制。然而，血管细胞中养分可用性如何影响它们的发育仍有待解决。在细胞水平上，细胞质中糖的可用性主要通过质膜上主动和/或易化运输的糖交换来调节。在拟南芥（Arabidopsis thaliana）中，质膜转运蛋白基因中，液泡膜蔗糖协同转运蛋白 16（SUGAR WILL EVENTUALLY BE EXPORTED TRANSPORTER 16，SWEET16）和 SWEET17 的表达先前已在血管系统中检测到。在这里，我们使用反向遗传学方法提出，质膜上的糖交换受 SWEET16 调控，这对于木质部细胞分裂很重要，这一点尤其体现在 swt16 突变体中木质部细胞数量减少和 SWEET16 在原形成层-木质部边界处的积累上。此外，我们证明了 SWEET16 和/或 SWEET17 介导的己糖转运对于维持木质部次生细胞壁的形成是必需的。这一结果与傅里叶变换红外光谱在 swt16swt17 双突变体中测量到的木质部细胞壁组成缺陷以及几个参与次生细胞壁合成的基因的上调相一致。因此，我们的工作支持了这样一种模型，即木质部发育部分依赖于木质部形成细胞液泡膜上己糖的交换。
