Germ cell cluster formation and cell death are alternatives in caste-specific differentiation of the larval honey bee ovary
Germ cell cluster formation and cell death are alternatives in caste-specific differentiation of the larval honey bee ovary
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DOI：
10.1080/07924259.1997.9672582
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发表时间：
1997-01-01
影响因子：
0.8
通讯作者：
Steinbruck, G
中科院分区：
文献类型：
--
作者：
Hartfelder, K;Steinbruck, G
雌性蜜蜂性腺的种姓特异性分化发生在第五龄幼虫。在女王幼虫大多数卵巢管表现出几乎同时形成的许多生殖细胞簇的前20小时内最后一个幼虫蜕皮。超微结构独特的梭体细胞质连接这些囊细胞。生殖细胞分化伴随着卵巢管、卵泡和终丝细胞的体细胞成分的形态学变化。随后，女王卵巢管延长和分化合并在一个基花萼的基柄。第二轮的有丝分裂活动被发现发生在后期预蛹和早期蛹后卵巢。这一轮可能会提高生殖细胞数量组成的每个集群中观察到的成年蜜蜂蜂王卵泡的水平。相反，在幼虫工蜂卵巢的120-160个卵巢管中的大多数中不发生生殖细胞簇的形成，而是在这样的卵巢管中的许多细胞显示出即将退化的迹象，例如大的自噬体。从工蜂卵巢中提取的DNA没有发现核小体梯状，超微结构上，生殖细胞核中的染色质完整。在小工蜂卵巢中存活的4-7个卵巢管中，发现了具有与蜂王卵巢管相同超微结构特征的生殖细胞簇。在最后一次幼虫蜕皮后不久，幼虫卵巢的发育途径开始分歧的时间窗口与保幼激素滴度的种姓特异性差异相吻合，长期以来，保幼激素滴度被认为是种姓特异性形态发生的关键。
Caste-specific differentiation of the female honey bee gonad takes place in the fifth larval instar. In queen larvae most ovarioles exhibit almost simultaneous formation of numerous germ cell clusters within the first 20 h after the last larval molt. Ultrastructurally distinctive fusomal cytoplasm connects these cystocytes. Germ cell differentiation is accompanied by morphological changes in somatic components of the ovarioles, the follicle and the terminal filament cells. Subsequently, queen ovarioles elongate and differentiate basal stalks that coalesce in a basal calyx. A second round of mitotic activity was found to occur in the late prepupal and early pupal queen ovary. This round may elevate germ cell numbers composing each cluster to levels observed in follicles of adult honey bee queens. In contrast, germ cell cluster formation does not occur in most of the 120-160 ovarioles of the larval worker ovary, but instead many cells in such ovarioles show signs of impending degeneration, such as large autophagic bodies. DNA extracted from worker ovaries did not reveal nucleosomal laddering, and ultrastructurally, chromatin in germ cell nuclei appeared intact. In the 4-7 surviving ovarioles of the small worker ovary, germ cell clusters were found with ultrastructural characteristics identical to those in queen ovarioles. The temporal window during which divergence in developmental pathways of the larval ovaries initiates shortly after the last larval molt coincides with caste-specific differences in juvenile hormone titer which have long been considered critical to caste-specific morphogenesis.