Maternal expression and early zygotic regulation of the Hox3/zen gene in the grasshopper Schistocerca gregaria
Maternal expression and early zygotic regulation of the Hox3/zen gene in the grasshopper Schistocerca gregaria
复制标题
DOI：
10.1046/j.1525-142x.2000.00065.x
复制
发表时间：
2000-09-01
影响因子：
2.9
通讯作者：
Akam, M
中科院分区：
文献类型：
--
作者：
Dearden, P;Grbic, M;Akam, M
在昆虫中，卵子早期形成图案的关键一步是区分胚胎本身的原基和那些将形成胚外膜的区域。在果蝇中，这些过程被很好地理解，胚胎外膜的结构是高度衍生的。低等昆虫特有的独特羊膜和浆膜被单一的羊膜和浆膜所取代。我们使用ZEN基因作为标记来研究蝗虫Schistocerca gregaria(非洲鼠疫蝗虫)胚胎外膜的形成和早期胚胎模式的其他方面。ZEN基因来源于HOX基因，但在果蝇中，它们似乎已经失去了对胚胎AIP轴形成模式的任何作用；相反，它们参与了D/V模式和胚胎外膜的指定。我们发现血吸虫10基因在胚胎发生过程中表达分为三个不同的阶段。第一个是在分裂期间，当SGZEN在到达细胞表面的所有能量中瞬时表达时。第二阶段的表达开始于围绕着形成的胚胎的一圈“项链细胞”，并划分了羊膜和浆膜之间的边界。这导致了整个浆膜的表达。最后一个表达阶段是羊膜，在羊膜从浆膜分离出来之后。这一复杂的模式表明，Sgzen在血吸虫中的作用不仅仅局限于胚胎外膜中细胞特性的指定。我们还报道了血吸虫Ten基因在母体中的表达，不同于果蝇和Tribolium的同源基因。一个独特的母体转录本和母体ZEN蛋白从减数分裂后的早期阶段积累在发育中的卵母细胞中。它们一直均匀地分布在卵母细胞的细胞质中，直到卵黄发生后期，此时蛋白质和RNA可能通过被动排斥卵黄而变得某种程度上集中在卵皮层和卵母细胞的后极帽。SGZEN蛋白在卵母细胞中的胞质定位，以及在胚胎发育的某些阶段，表明该转录因子的核排斥是特异控制的。
In insects, a key step in the early patterning of the egg is to distinguish the primordium of the embryo proper from those regions that will form extra-embryonic membranes. In Drosophila, where these processes are well understood, the structure of the extra-embryonic membranes is highly derived. The distinct amnion and serosa typical of lower insects is replaced by a single. fused, and much reduced membrane, the amnioserosa, which never secretes an embryonic cuticle.We have used the Zen gene as a marker to study the formation of the extra-embryonic membranes, and other aspects of early embryonic patterning, in the grasshopper Schistocerca gregaria (African Plague Locust). Zen genes are derived from Hox genes, but in Drosophila they appear to have lost any role in patterning the AIP axis of the embryo; instead, they are involved in D/V patterning and the specification of the extra-embryonic membranes.We show that the Schistocerca ten gene is expressed during embryogenesis in three distinct phases. The first of these is during cleavage, when Sgzen is transiently expressed in all energids that reach the cell surface. The second phase of expression initiates in a ring of "necklace cells" that surround the forming embryo, and demarcate the boundary between the amnion and serosa. This leads to expression throughout the serosa. The final phase of expression is in the amnion, after this has separated from the serosa. This complex pattern implies that the role of Sgzen in Schistocerca is not limited solely to the specification of cell identity in the extra-embryonic membranes.We also report that the Schistocerca ten gene is expressed maternally, unlike its Drosophila and Tribolium counterparts. A distinct maternal transcript, and maternal Zen protein, accumulate in the developing oocyte from early post-meiotic stages. They remain uniformly distributed in the oocyte cytoplasm until late vitellogenic stages, when the protein and RNA become somewhat concentrated at the egg cortex and in the posterior polar cap of the oocyte, probably by passive exclusion from the yolk. The cytoplasmic localization of Sgzen protein in the oocyte, and at some stages during embryogenesis, implies that nuclear exclusion of this transcription factor is specifically controlled.