Huang Sheng, Yamaji Naoki, Konishi Noriyuki, Mitani-Ueno Namiki, Ma Jian Feng
Institute of Plant Science and Resources, Okayama University, Chuo 2-20-1, Kurashiki, 710-0046, Japan.
New Phytol. 2025 Aug;247(3):1280-1289. doi: 10.1111/nph.70110. Epub 2025 Apr 1.
Silicon (Si) is highly accumulated in both the leaf blade and sheath of rice, but the transporter mediating the local distribution of Si between these two tissues remains unidentified. We investigated the role of an aquaporin, OsLsi6, in the local distribution of Si in rice leaves. We also examined the interrelations between vascular structure and OsLsi6 function in xylem unloading of Si for its local distribution. OsLsi6 is polarly localized at the xylem parenchyma cells of both the large and small vascular bundles of the leaf blade and sheath. OsLsi6 was downregulated by Si supply at the leaf sheath but not in the leaf blade. The knockout of OsLsi6 increased the distribution of Si and germanium (Ge) to the leaf blade while reducing their distribution to the leaf sheath. The mestome sheath surrounding the vascular bundle was suberized in leaf sheaths and in large vascular bundles of leaf blades, but not in small vascular bundles of leaf blades. Our results indicate that there are two pathways for xylem unloading of Si for its local distribution: the OsLsi6-dependent symplastic pathway in the leaf sheath and large vascular bundles of the leaf blade, and the apoplastic pathway in the small vascular bundle of the leaf blade.
硅（Si）在水稻叶片和叶鞘中均高度积累，但介导硅在这两个组织之间局部分布的转运体仍未明确。我们研究了水通道蛋白OsLsi6在水稻叶片硅局部分布中的作用。我们还研究了维管结构与OsLsi6功能在硅木质部卸载以进行局部分布过程中的相互关系。OsLsi6极性定位在叶片和叶鞘大小维管束的木质部薄壁细胞中。在叶鞘中，硅供应会下调OsLsi6的表达，但在叶片中不会。敲除OsLsi6会增加硅和锗（Ge）向叶片的分布，同时减少它们向叶鞘的分布。围绕维管束的后生皮层在叶鞘和叶片的大维管束中栓化，但在叶片的小维管束中不栓化。我们的结果表明，硅木质部卸载以进行局部分布有两条途径：叶鞘和叶片大维管束中依赖OsLsi6的共质体途径，以及叶片小维管束中的质外体途径。
