Somashekar Harsha, Takanami Keiko, Benitez-Alfonso Yoselin, Oishi Akane, Hiratsuka Rie, Nonomura Ken-Ichi
Plant Cytogenetics Laboratory, National Institute of Genetics, Mishima, Japan.
School of Life Science, The Graduate University for Advanced Studies, SOKENDAI, Hayama, Kanagawa, Japan.
Ann Bot. 2024 Dec 31;134(6):1013-1026. doi: 10.1093/aob/mcae137.
Fertilization relies on pollen mother cells able to transition 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 onset of meiosis, the cellulose content in 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.
We carried out electron microscopic, aniline blue and renaissance staining 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 maintenance of plasmodesmata. 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 the transition from mitosis to meiosis is necessary to maintain cell-to-cell connections and optimal extracellular distance among the central anther locular cells. The findings of this study contribute to our understanding of the regulatory influence of callose metabolism during initiation of meiosis in flowering plants.
受精依赖于能够从有丝分裂转变为减数分裂以提供配子的花粉母细胞。这一过程涉及分子、细胞和生理水平上的显著变化，包括（但不限于）细胞壁的重塑。在减数分裂开始时，花粉母细胞壁中的纤维素含量逐渐下降，同时多糖胼胝质在花药室中沉积。我们旨在了解花粉母细胞壁中纤维素向胼胝质转变的生物学意义。
我们对水稻花进行了电子显微镜、苯胺蓝和复兴染色分析。
我们的观察表明，在野生型水稻花药中，有丝分裂向减数分裂的转变与称为胞间连丝的细胞质连接数量逐渐减少相吻合。水稻胼胝质合成酶GSL5（Osgsl5 - 3）的一个突变体，在减数分裂前和减数分裂期花药中的胼胝质积累受损，花粉母细胞和绒毡层细胞之间的胞间连丝频率有更大程度的降低，表明胼胝质在维持胞间连丝方面发挥作用。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著增加以及减数分裂前细胞形态受损。
结果表明，从有丝分裂到减数分裂转变过程中胼胝质向纤维素的转变对于维持花药中央室细胞之间的细胞间连接和最佳细胞外距离是必要的。本研究结果有助于我们理解开花植物减数分裂起始过程中胼胝质代谢的调控影响。
