Swalla B J, Makabe K W, Satoh N, Jeffery W R
Department of Zoology, University of California, Davis, Bodega Bay 94923.
Development. 1993 Oct;119(2):307-18. doi: 10.1242/dev.119.2.307.
We have used a subtractive procedure to isolate cDNA clones encoding genes expressed differentially in ascidian species with alternate modes of development. The ascidians used in this study were Molgula occulta, which develops a tailed (urodele) larva, and Molgula occulta, which develops a tailless (anural) larva. Two of the identified clones, Uro-2 and Uro-11, are described. Southern blots show that the Uro-2 and Uro-11 genes are present in both species, but the corresponding mRNAs are expressed preferentially in the urodele species. In situ hybridization showed that Uro-2 and Uro-11 transcripts accumulate in small oocytes during oogenesis. The maternal Uro-2 and Uro-11 transcripts were distributed throughout the oocyte cytoplasm. Transcript concentrations declined during vitellogenesis, but mature eggs still contain detectable levels of Uro-2 and Uro-11 mRNA. After fertilization, the maternal Uro-2 and Uro-11 transcripts were localized in the ectoplasm of uncleaved zygotes and mostly entered the ectoderm cells during cleavage. The Uro-2 gene appears to produce only maternal transcripts. In contrast, the Uro-11 gene may also produce zygotic transcripts, which accumulate between gastrulation and neurulation in posterior epidermis, neural and tail muscle cells. Zygotic expression of the Uro-11 gene was not detected in embryos of the anural species. The deduced amino acid sequences of the Uro-2 and Uro-11 cDNAs suggest that they encode novel basic proteins with distinctive structural features. The predicted Uro-2 protein contain, a leucine zipper motif, suggesting that it may dimerize with another protein. The predicted Uro-11 protein contains a nuclear localization signal, a region with similarity to part of the DNA-binding motif in the bacterial histone-like HU and IHF proteins, 12 repeats of the proposed DNA-binding motif S(T)PXX, and a potential zinc finger of the C6 or C6H2 class, suggesting that it may be a DNA-binding protein. The Uro-2 and Uro-11 proteins are candidates for regulatory factors involved in the evolutionary transition from urodele to anural development.
我们采用了消减程序来分离编码在具有不同发育模式的海鞘物种中差异表达基因的cDNA克隆。本研究中使用的海鞘是发育出有尾（尾海鞘纲）幼虫的隐匿住囊虫和发育出无尾（无尾纲）幼虫的隐匿住囊虫。描述了两个已鉴定的克隆，即Uro - 2和Uro - 11。Southern杂交显示Uro - 2和Uro - 11基因在这两个物种中均存在，但相应的mRNA优先在尾海鞘纲物种中表达。原位杂交表明，Uro - 2和Uro - 11转录本在卵子发生过程中在小卵母细胞中积累。母体Uro - 2和Uro - 11转录本分布于整个卵母细胞细胞质中。在卵黄发生过程中转录本浓度下降，但成熟卵子仍含有可检测水平的Uro - 2和Uro - 11 mRNA。受精后，母体Uro - 2和Uro - 11转录本定位于未分裂合子的外质中，并且在分裂过程中大多进入外胚层细胞。Uro - 2基因似乎只产生母体转录本。相比之下，Uro - 11基因可能也产生合子转录本，这些转录本在原肠胚形成和神经胚形成之间在后表皮、神经和尾部肌肉细胞中积累。在无尾纲物种的胚胎中未检测到Uro - 11基因的合子表达。Uro - 2和Uro - 11 cDNA的推导氨基酸序列表明它们编码具有独特结构特征的新型碱性蛋白。预测的Uro - 2蛋白含有一个亮氨酸拉链基序，表明它可能与另一种蛋白二聚化。预测的Uro - 11蛋白含有一个核定位信号、一个与细菌类组蛋白HU和IHF蛋白中部分DNA结合基序相似的区域、提议的DNA结合基序S(T)PXX的12个重复序列以及一个C6或C6H2类的潜在锌指，表明它可能是一种DNA结合蛋白。Uro - 2和Uro - 11蛋白是参与从尾海鞘纲到无尾纲发育进化转变的调控因子的候选蛋白。
