Department of Biology, College of Arts and Science, University of Saskatchewan, Saskatoon, S7N 5E2, Saskatchewan, Canada.
Plant Cell. 2021 May 5;33(3):623-641. doi: 10.1093/plcell/koaa036.
Leaf spongy mesophyll cells form an interconnected network of branched cells and intercellular spaces to maximize the surface area available for light capture and photosynthetic gas exchange. To investigate the morphogenetic events leading to cell separation and branching in Arabidopsis thaliana, we used mesophyll-specific promoters to facilitate imaging of mesophyll cell shape and microtubule (MT) organization over multiple spatiotemporal scales without interference from the overlying epidermal cells. We show that cells enlarge by selective expansion of cell wall regions in contact with intercellular spaces. Cell-cell contacts remain relatively fixed in size, forming the termini of interconnecting branches. Surprisingly, classic schizogeny (de-adhesion of neighboring cells) is relatively infrequent, being related to the local topology of cell junctions during early expansion. Intercellular spaces cue the position of stable MT bundles, which in turn promote efficient dilation of intercellular spaces and cell branching. Our data provide insights into mesophyll morphogenesis and MT organization and lay the groundwork for future investigations.
叶肉海绵状细胞形成一个分支细胞和细胞间隙的相互连接的网络，以最大限度地提高用于捕获光和光合作用气体交换的表面积。为了研究导致细胞分离和分枝的形态发生事件，我们使用了叶肉特异性启动子，以便在不干扰上面的表皮细胞的情况下，在多个时空尺度上促进对叶肉细胞形状和微管（MT）组织的成像。我们表明，细胞通过与细胞间隙接触的细胞壁区域的选择性扩展而增大。细胞-细胞接触的大小相对固定，形成互连分支的末端。令人惊讶的是，经典的分裂（相邻细胞的去黏附）相对较少，这与早期扩展过程中细胞连接的局部拓扑结构有关。细胞间隙提示稳定的 MT 束的位置，这反过来又促进细胞间隙的有效扩张和细胞分支。我们的数据提供了对叶肉形态发生和 MT 组织的深入了解，并为未来的研究奠定了基础。
