Ibnsouda S, Schweisguth F, de Billy G, Vincent A
Centre de Biologie du Développement, Toulouse, France.
Development. 1993 Oct;119(2):471-83. doi: 10.1242/dev.119.2.471.
A dramatic reorganization of the cytoskeleton underlies the cellularisation of the syncytial Drosophila embryo. Formation of a regular network of acto-myosin filaments, providing a structural framework, and possibly a contractile force as well, appears essential for the synchronous invagination of the plasma membrane between adjacent nuclei. The serendipity alpha (sry alpha) gene is required for this complete reorganization of the microfilaments at the onset of membrane invagination. We compare here the structure and expression of sry alpha between D. pseudoobscura, D. subobscura and D. melanogaster. Interspersion of evolutionarily highly conserved and divergent regions is observed in the protein. One such highly conserved region shows sequence similarities to a motif found in proteins of the ezrin-radixin-moesin (ERM) family. Four 7-13 bp motifs are conserved in the 5' promoter region; two of these are also found, and at the same position relative to the TATA box, in nullo, another zygotic gene recently shown to be involved in cellularisation. The compared patterns of expression of D. melanogaster sry alpha and nullo, and D. pseudoobscura sry alpha reveal a complex regulation of the spatiotemporal accumulation of their transcripts. The D. pseudoobscura sry alpha gene is able to rescue the cellularisation defects associated with a complete loss of sry alpha function in D. melanogaster embryos, even though species-specific aspects of its expression are maintained. Despite their functional homologies, the D. melanogaster and D. pseudoobscura sry alpha RNAs have different subcellular localisations, suggesting that this specific localization has no conserved role in targeting the sry alpha protein to the apical membranes.
细胞骨架的剧烈重组是果蝇合胞体胚胎细胞化的基础。肌动蛋白 - 肌球蛋白丝形成规则网络，不仅提供结构框架，还可能提供收缩力，这对于相邻细胞核间质膜的同步内陷似乎至关重要。在膜内陷开始时，意外α（sryα）基因是微丝完全重组所必需的。我们在此比较了拟暗果蝇、次暗果蝇和黑腹果蝇之间sryα的结构和表达。在该蛋白质中观察到进化上高度保守和不同区域的散布。其中一个这样的高度保守区域显示出与埃兹蛋白 - 根蛋白 - 膜突蛋白（ERM）家族蛋白质中发现的基序具有序列相似性。在5'启动子区域有四个7 - 13 bp的基序是保守的；其中两个在nullo基因中也被发现，且相对于TATA框处于相同位置，nullo是另一个最近显示参与细胞化的合子基因。黑腹果蝇sryα和nullo以及拟暗果蝇sryα的比较表达模式揭示了它们转录本时空积累的复杂调控。拟暗果蝇sryα基因能够挽救与黑腹果蝇胚胎中sryα功能完全丧失相关的细胞化缺陷，尽管其表达的物种特异性方面得以保留。尽管它们在功能上具有同源性，但黑腹果蝇和拟暗果蝇的sryα RNA具有不同的亚细胞定位，这表明这种特定定位在将sryα蛋白靶向顶端膜方面没有保守作用。
