Abstract
Cellulose microfibrils reinforce the cell wall for morphogenesis in plants. Herein, we provide evidence on a series of defects regarding stomatal complex development and F-actin organization in Zea mays leaf epidermis, due to inhibition of cellulose synthesis. Formative cell divisions of stomatal complex ontogenesis were delayed or inhibited, resulting in lack of subsidiary cells and frequently in unicellular stomata, with an atypical stomatal pore. Guard cells failed to acquire a dumbbell shape, becoming rounded, while subsidiary cells, whenever present, exhibited aberrant morphogenesis. F-actin organization was also affected, since the stomatal complex-specific arrays were scarcely observed. At late developmental stages, the overall F-actin network was diminished in all epidermal cells, although thick actin bundles persisted. Taken together, stomatal complex development strongly depends on cell wall mechanical properties. Moreover, F-actin organization exhibits a tight relationship with the cell wall.
Highlights
Plant cells are confined by the cell wall, a rigid container consisting of several polysaccharides, as well as proteins and other materials [1]
Cellulose microfibril orientation is dictated by cortical microtubule organization, as cellulose synthase complexes at the plasma membrane slide along microtubules, while depositing newly-synthesized microfibrils in the cell wall, albeit the presence of microtubules is not required for cellulose synthase movement per se [3]
This regulatory effect of cortical microtubule organization on cellulose microfibril patterning is responsible for the shaping of simple cells, such as elongated root epidermal cells, as well as elaborate ones, like lobed mesophyll and ordinary epidermal cells, which are called “pavement cells” [4]
Summary
Plant cells are confined by the cell wall, a rigid container consisting of several polysaccharides, as well as proteins and other materials [1]. Cellulose microfibril orientation is dictated by cortical microtubule organization, as cellulose synthase complexes at the plasma membrane slide along microtubules, while depositing newly-synthesized microfibrils in the cell wall, albeit the presence of microtubules is not required for cellulose synthase movement per se [3]. This regulatory effect of cortical microtubule organization on cellulose microfibril patterning is responsible for the shaping of simple cells, such as elongated root epidermal cells, as well as elaborate ones, like lobed mesophyll and ordinary epidermal cells, which are called “pavement cells” [4]. Thick subcortical F-actin bundles are engaged in the elementary function of cytoplasmic streaming, essential for the distribution and motility of the cytoplasm in vacuolated plant cells, while they orchestrate the movement and location of several organelles, such as the nucleus, endoplasmic
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