昆虫精细胞内中心粒附体的来源和作用

ORIGIN AND FUNCTION OF THE CENTRIOLE ADJUNCT IN SPERMATIDS OF INSECTS

本研究应用界面铺浮和超薄切片技术,观察了东亚飞蝗(Locusta migratoria manilensis)和七星瓢虫(Coccinella septempunctata L.)精细胞内中心粒附体(CA)的形成和作用。结果发现,作为电子致密依的CA前体和原顶体颗粒出现在副核和细胞核之间区域。随后,这个主要是由约300颗粒组成的CA前体附着在核膜,核内、外膜加厚。在副核分化成两个线粒体衍生物或稍早些时刻,近心中心粒移向CA并嵌入。中心粒镶嵌到核膜上发育成基体,由此生长出轴丝来。随着精细胞的延长,CA的形状也跟着转变和伸长。 250—300染色质纤维沿精细胞长纵轴连接在CA结构的基部。当精细胞核向长形转变时,染色质纤维解旋并结合在一起形成缎带结构。因此,可以设想CA是作为暂时性细胞器在组织精细胞内,染色质纤维重新组织排列和指导中心粒移向精细胞核的特定区域中起作用。

The formation and function of centriole adjunct (CA) in spermatids of Locu-sta migratoria and Coccinella septempunctata are studied by electron microscopy with ultra-thin section and water spreading techniques. It is found that the CA is an electron dense body and the proacrosomal granule appear in the region between the nucleus and the nebenkern. Later, the pre-centriole adjunct which mainly consists of 300 A granules is attached to the nuclear membrane, of which the inner and outer components then become thickened. As the nebenkern differentiates into two mi-tochondrial derivatives or a bit earlier, the proximal centnole migrates to the CA and is finally surrounded by the CA. As a basal body it is anchored on the nuclear envelope and the axoneme originates from it. Following the spermatid elongation, the shape of CA is progressively transformed and extended. The 250-300 A chromatin fibers along the longitudinal axis of the spermatid are attached to the base of CA structure. As spermatid nucleus elongates, the chromatin fibers are unwound and join together to form ribbon structure. It is assumed that the CA is a transient organelle and its role is to organize the rearragement of chromatin in the spermatid and to direct the migration of the centriole to the nuclear region from the place where the flagellum extends.