Department of Biological Sciences, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033 Japan.
Department of Biological Sciences, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka, 560-0043 Japan.
Plant Cell Physiol. 2020 Feb 1;61(2):255-264. doi: 10.1093/pcp/pcaa002.
Stem cells undergo cell division and differentiation to ensure organized tissue development. Because plant cells are immobile, plant stem cells ought to decide their cell fate prior to differentiation, to locate specialized cells in the correct position. In this study, based on a chemical screen, we isolated a novel secondary cell wall indicator BF-170, which binds to lignin and can be used to image in vitro and in situ xylem development. Use of BF-170 to observe the vascular differentiation pattern in the in vitro vascular cell induction system, VISUAL, revealed that adaxial mesophyll cells of cotyledons predominantly generate ectopic xylem cells. Moreover, phloem cells are abundantly produced on the abaxial layer, suggesting the involvement of leaf adaxial-abaxial polarity in determining vascular cell fate. Analysis of abaxial polarity mutants highlighted the role of YAB3, an abaxial cell fate regulator, in suppressing xylem and promoting phloem differentiation on the abaxial domains in VISUAL. Furthermore, YABBY family genes affected in vivo vascular development during the secondary growth. Our results denoted the possibility that such mediators of spatial information contribute to correctly determine the cell fate of vascular stem cells, to conserve the vascular pattern of land plants.
干细胞通过细胞分裂和分化来确保组织的有序发育。由于植物细胞是不能移动的，因此植物干细胞应该在分化之前决定其细胞命运，以便将特化细胞定位到正确的位置。在这项研究中，我们基于化学筛选分离到一种新型次生细胞壁标志物 BF-170，它与木质素结合，可以用于体外和原位木质部发育的成像。使用 BF-170 观察体外血管细胞诱导系统 VISUAL 中的血管分化模式，结果表明子叶的近轴叶肉细胞主要产生异位木质部细胞。此外，韧皮部细胞在远轴层大量产生，这表明叶片近轴-远轴极性参与决定血管细胞命运。对远轴极性突变体的分析突出了 YAB3（一种远轴细胞命运调节剂）的作用，它在 VISUAL 中抑制远轴区的木质部形成并促进韧皮部分化。此外，在次生生长过程中，YABBY 家族基因影响体内血管发育。我们的结果表明，这些空间信息的介导物可能有助于正确确定血管干细胞的细胞命运，以保留陆地植物的血管模式。
