Dallai Romano, Paoli Francesco, Mercati David, Lupetti Pietro
Department of Life Sciences, University of Siena, via Aldo Moro 2, 53100 Siena, Italy.
Consiglio per la Ricerca in Agricoltura e l'analisi dell'economia agraria, Centro di Ricerca per l'Agrobiologia e la Pedologia (CREA-ABP), via di Lanciola 12/a, Cascine del Riccio, 50125 Firenze, Italy.
Tissue Cell. 2016 Apr;48(2):104-13. doi: 10.1016/j.tice.2016.02.001. Epub 2016 Feb 19.
The ancestral eukaryotes presumably had an MTOC (microtubule organizing center) which late gave origin to the centriole and the flagellar axoneme. The centrosome of insect early spermatids is in general composed of two components: a single centriole and a cloud of electron-dense pericentriolar material (PCM). During spermiogenesis, the centriole changes its structure and gives rise to a flagellar axoneme, while the proteins of PCM, gamma tubulin in particular, are involved in the production of microtubules for the elongation and shaping of spermatid components. At the end of spermiogenesis, in many insects, additional material is deposited beneath the nucleus to form the centriole adjunct (ca). This material can also extend along the flagellum in two accessory bodies (ab) flanking the axoneme. Among Homoptera Sternorrhyncha, a progressive modification of their sperm flagella until complete disappearance has been verified. In the Archaeococcidae Matsucoccus feytaudi, however, a motile sperm flagellum-like structure is formed by an MTOC activity. This finding gives support to the hypothesis that an evolutionary reversal has occurred in the group and that the cell, when a non-functional centriole is present, activates an ancestral structure, an MTOC, to form a polarized motile bundle of microtubules restoring sperm motility. The presence and extension of the centriole adjunct in the different insect orders is also enlisted.
推测祖先真核生物具有一个微管组织中心（MTOC），该中心后来产生了中心粒和鞭毛轴丝。昆虫早期精子细胞的中心体通常由两个部分组成：一个单一的中心粒和一团电子致密的中心粒周围物质（PCM）。在精子发生过程中，中心粒改变其结构并产生鞭毛轴丝，而PCM的蛋白质，特别是γ微管蛋白，参与微管的产生，用于精子细胞成分的伸长和塑形。在精子发生结束时，在许多昆虫中，额外的物质沉积在细胞核下方以形成中心粒附属物（ca）。这种物质也可以沿着鞭毛在轴丝两侧的两个附属体（ab）中延伸。在同翅目胸喙亚目昆虫中，已经证实它们的精子鞭毛会逐渐改变直至完全消失。然而，在古球蚧科的松突圆蚧中，一种类似活动精子鞭毛的结构是由MTOC活动形成的。这一发现支持了这样一种假设，即在该类群中发生了进化逆转，并且当存在无功能的中心粒时，细胞会激活一种祖先结构，即MTOC，以形成极化的活动微管束，恢复精子的运动能力。文中还列举了不同昆虫目中中心粒附属物的存在情况及其延伸情况。
