Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan.
Bio-Next Project, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Yamate Building #3, 5-1, Higashiyama, Myodaiji, Okazaki, Aichi, 444-8787, Japan.
New Phytol. 2019 Apr;222(2):1101-1111. doi: 10.1111/nph.15649. Epub 2019 Jan 22.
To reveal the mode of morphogenesis of flattened unifacial leaves, we analysed the cell division direction and distribution on the leaf blade of Juncus prismatocarpus. Using the pulse-chase 5-ethynyl-2'-deoxyuridine method, we quantified and mapped the cell division direction on the leaf blade of J. prismatocarpus and compared the distribution of thickening cell divisions with the expression pattern of DROOPING LEAF (DL), a key gene involved in leaf blade thickening. Thickening cell divisions were the most abundant (> 45%) among all cell division directions on the leaf blade of J. prismatocarpus from the early plastochron 2 stage through the plastochron 3 stage. Mapping of cell divisions indicated that cell divisions in a particular direction were not restricted to a particular domain but were distributed diffusely throughout the entire cross-sectional area of the leaf blade. Gradient analysis indicated that the distribution of thickening cell divisions of the adaxial domain was denser than that of the abaxial domain. Contrary to the prolonged and diffuse distribution of thickening cell divisions, DL expression was transient and restricted in a narrow band. Our results suggest that a diffuse 'thickening meristem' plays the key role in the development of flattened unifacial leaves.
为了揭示扁平单叶的形态发生模式，我们分析了香蒲属植物棱柱叶的叶片细胞分裂方向和分布。使用脉冲追踪 5-乙炔基-2'-脱氧尿苷法，我们对棱柱叶的细胞分裂方向进行了量化和定位，并将加厚细胞分裂的分布与涉及叶片加厚的关键基因“垂叶（DL）”的表达模式进行了比较。在棱柱叶的早期原基 2 期到原基 3 期，加厚细胞分裂在所有细胞分裂方向中最为丰富（>45%）。细胞分裂的定位表明，特定方向的细胞分裂并不局限于特定区域，而是在叶片的整个横截面上广泛分布。梯度分析表明，腹面域的加厚细胞分裂分布比背面域更密集。与加厚细胞分裂的延长和弥散分布相反，DL 表达是短暂的，并局限在一个狭窄的带中。我们的结果表明，弥散的“加厚分生组织”在扁平单叶的发育中起着关键作用。
