Developmentally and environmentally regulated expression of gamone 1:: the trigger molecule for sexual reproduction in Blepharisma japonicum
Developmentally and environmentally regulated expression of gamone 1:: the trigger molecule for sexual reproduction in Blepharisma japonicum
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DOI：
10.1242/jcs.02359
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发表时间：
2005-06-15
影响因子：
4
通讯作者：
Harumoto, T
中科院分区：
文献类型：
--
作者：
Sugiura, M;Kawahara, S;Harumoto, T
原生动物纤毛虫的有性生殖（交配）是由互补交配类型的细胞之间的特定细胞-细胞相互作用诱导的。祖先纤毛虫ble法利赛马日本有两种交配类型，I和II。在这种细胞外相互作用中作为信号分子的物质被称为激素。由交配的I型细胞产生的糖蛋白γ - 1是触发这种相互作用的关键因素。我们之前已经分离出了gamone 1并确定了其完整的氨基酸序列。为了阐明纤毛虫偶联起始的机制，我们研究了gamone I基因的转录，发现它受多种内外因素的控制。当性成熟的交配型I细胞被饥饿时，特异地出现了gamone I基因转录。未成熟细胞、交配11型细胞和增殖细胞均未检测到。当I型细胞受到H型细胞分泌的γ - 2刺激时，转录水平明显升高。这是首次报道纤毛虫体内的激素基因转录受到发育和环境因素的严格调控。本研究表明，gamone I转录的开始与有丝分裂增殖细胞向分化的预接合体的转换机制、克隆发育中未成熟细胞向成熟细胞的分化机制以及确保交配类型特异性基因沉默的机制有关。
Sexual reproduction (conjugation) in protozoan ciliates is induced by specific cell-cell interactions between cells of complementary mating types. The ancestral ciliate Blepharisma japonicum has two mating types, I and II. The substances that act as signaling molecules in this extracellular interaction for conjugation are called gamones. The glycoprotein gamone 1, produced by mating type I cells, is a key factor that triggers this interaction. We have previously isolated gamone 1 and determined its complete amino acid sequence. To elucidate the mechanism of initiation of conjugation in ciliates, we investigated the transcription of the gamone I gene and found that it is controlled by various internal and external factors. The gamone I gene transcript appeared specifically when sexually mature mating type I cells were starved. It was not detected in immature cells, mating type 11 cells or proliferating cells. The level of transcription was markedly increased in type I cells when they were stimulated with gamone 2, which is secreted by type H cells. This is the first report that the transcription of gamone genes in ciliates is strictly regulated by developmental and environmental factors. This study suggests that the onset of transcription of gamone I is linked to the switching mechanism that converts mitotically proliferating cells to differentiated preconjugants, the mechanism of differentiation from immature to mature cells in clonal development, and the mechanism that ensures mating type-specific gene silencing.