葫芦藓精子发生过程中胞间连丝与胞质桥的超微结构

从超微结构水平上对葫芦藓(Funaria hygrometrica Hedw.)精子发生过程中胞间连接系统的结构及其变化动态进行了研究。结果表明,同一区中的相邻生精细胞由大量胞质桥相连,而不同区的细胞之间则不存在胞质桥。胞间连丝存在于套细胞之间以及套细胞与生精细胞之间, 但它在生精细胞间不存在。在精子器发生的后期,当精子细胞壁开始降解时,同一个精子器中所有的精子细胞似乎都由扩大的胞质桥相互连接。胞质桥一直保持到精子分化的后期,最终精子细胞同步分化成精子。胞间连丝与胞质桥具有不同的内部结、分布以及生物发生机制,这表明它们在精子器的发育过程中可能扮演着不同的角色。

Ultrastructural Aspects of Plasmodesmata and Cytoplasmic Bridges During Spermatogenesis in Funaria hygrometrica

Cytoplasmic bridge, as a broader cellular connection structure, exists in plants from Volvox tohigher plants, but has been subjected to less investigation as compared to plasmodesmata. It has beenspeculated that the structure may be related to the synchronization of cell division and developmentduring the microsporegenesis and spermatogenesis. During spermatogenesis in bryophytes, thespermatogenous cells are divided into several domains within an antheridium, and their divisions aresynchronous. However, their cellular connection system has not been investigated systematically. In thisstudy, we undertook an ultrastructural examination of the structure and dynamics of the intercellularconnection system during the spermatogenesis in Funaria hygrometrica Hedw. The result revealed thatwithin each individual domain, synchronously dividing spermatogenous cells were connected with eachother by numerous cytoplasmic bridges, which were absent in the walls between different domains. Theplasmodesmata connected spermatogenous cells with the cells of jacket layer, and also existed betweenthe jacket layer cells, but absent in the walls between the developing spermatogenous cells. At the latestage of the antheridial development, as the cell wall began to degrade, all of the spermatid cells within anantheridium seem connected with each other by the expanded cytoplasmic bridges. The cytoplasmicbridges retained to the late stage of spermatids differentiation, and finally, the spermatids synchronouslydifferentiated into spermatozoids. The different internal structures, biogenesis mechanisms and distributionbetween the plasmodesmata and cytoplasmic bridges suggest that they may play distinct roles during thedevelopment of antheridia.