Abstract：
Fertilization relies on pollen mother cells able to transit from mitosis to meiosis to supply gametes. This process involves remarkable changes at the molecular, cellular and physiological levels including (but not limited to) remodelling of the cell wall. During the meiosis onset, cellulose content at the pollen mother cell walls gradually declines with the concurrent deposition of the polysaccharide callose in anther locules. We aim to understand the biological significance of cellulose-to-callose turnover in pollen mother cells walls using electron microscopic analyses of rice flowers. Our observations indicate that in wild type rice anthers, the mitosis-to-meiosis transition coincides with a gradual reduction in the number of cytoplasmic connections called plasmodesmata. A mutant in the Oryza sativa callose synthase GSL5 (Osgsl5-3), impaired in callose accumulation in premeiotic and meiotic anthers, displayed a greater reduction in plasmodesmata frequency among pollen mother cells and tapetal cells suggesting a role for callose in plasmodesmata maintenance. In addition, a significant increase in extracellular distance between pollen mother cells and impaired premeiotic cell shaping was observed in the Osgsl5-3 mutant. The results suggest that callose-to-cellulose turnover during mitosis-meiosis transition is necessary to maintain cell-to-cell connections and optimal extracellular distance among the central anther locular cells. Findings of this study contribute to our understanding of the regulatory influence of callose metabolism during meiosis initiation in flowering plants.
摘要：
受精依赖于能够从有丝分裂过渡到减数分裂以供应配子的花粉母细胞。这个过程涉及分子的显著变化，细胞和生理水平,包括(但不限于)细胞壁的重塑。在减数分裂发作期间，随着多糖call的同时沉积在花药小室中，花粉母细胞壁上的纤维素含量逐渐下降。我们旨在通过对水稻花的电子显微镜分析来了解花粉母细胞壁中纤维素到call的周转的生物学意义。我们的观察表明，在野生型水稻花药中，有丝分裂到减数分裂的转变与胞质连接的数量逐渐减少同时发生。水稻callose合酶GSL5（Osgsl5-3）中的突变体，减数分裂前期和减数分裂花药中call的积累受损，在花粉母细胞和绒毡层细胞中显示出胞浆频率的降低幅度更大，表明call骨在胞浆维持中的作用。此外,在Osgsl5-3突变体中观察到花粉母细胞之间的细胞外距离显着增加和减数分裂前细胞形状受损。结果表明，有丝分裂-减数分裂过渡过程中call的call的纤维素转化对于维持中央花药室细胞之间的细胞间连接和最佳的细胞外距离是必要的。这项研究的结果有助于我们理解开花植物减数分裂过程中call体代谢的调节作用。
