Study on the mechanism in the cell cycle synchronization in the algal multinucleate cells

多核细胞存在于许多生物体中，包括真菌、动物和植物。在多核绿色藻类中，有丝分裂的模式有多种，在真藓类中，有丝分裂的模式有多种。每个核都独立分裂。在Boergesenia中，几乎同步的核分裂发生在离散的斑块中。而在Acrosiphonia中，细胞内几乎所有的核都是同步分裂的，当考虑到p34和cyclins对细胞周期的调控时，<cdc2>这些现象在多核绿色藻类中是不寻常的。在这项研究中，我试图用细胞周期的方法来研究绿色藻类的细胞周期调控机制。利用细胞学和分子生物学技术，从顶管藻中分离到一个与cdc2基因同源的cDNA克隆，并对其核苷酸序列和推导的氨基酸序列进行了测定，推测的氨基酸序列与酵母cdc2蛋白激酶的同源性为47.2%，用单克隆抗体进行分析表明，顶管藻cdc2蛋白激酶的氨基酸序列与酵母cdc2蛋白激酶的氨基酸序列同源性为47.2（PSTAIRE抗体）对cdc2蛋白激酶的特异性识别结果表明，cdc2蛋白激酶的分子量为Mr 38,000，真核生物cdc2基因编码的蛋白激酶的分子量一般为Mr 34,000，因此顶管藻cdc2蛋白激酶的分子量是非常独特的，结果表明，多核绿色藻的细胞周期调控可能是由与其他真核生物差异较大的cdc 2基因产物完成的。

Multinucleate cells have been reported in many organisms, including fungi, animals and plants.It is well known that the cell cycle (or, proceeding of DNA synthesis and mitosis) of each nucleus in the multinucleate cells pregresses synchronously.While, in multinucleate green algae, several types of mitotic pattern can be observed.In Bryopsis, each nucleus divides independently.Almost synchronous nuclear division occurs in discrete patches in Boergesenia.And in Acrosiphonia, almost all nuclei in the cell divide synchronously.When considering the cell cycle regulation by p34^<cdc2> and cyclins, these phenomena in the multinucleate green algae are unusual.In this study.I tried to examine the mechanism in the cell cycle regulation in the green algae using cytological and molecular biological techniques.Especially, a cDNA clone of Acrosiphonia that is homologous to the cdc2 genes was isolated using PCR,and its nucleotide and deduced amino acid sequences was determined.Putative amino acid sequence of Acrosiphonia cdc2 gene showed 47.2% homology to yeast cdc2 protein kinase.When analyzed with a monoclonal antibody (PSTAIRE antibody) against a cdc2 protein kinase, a band of Mr38,000 was recognized.Protein kinase encoded in cdc2 gene of the eukaryotes has always ahown Mr34,000, therefore, the molecular weight of Acrosiphonia cdc2 protein kinase was very unique.Adding to it, the antibody could not detect any protein in Bryopsis and Boergesenia.These results might suggest that the regulation in the cell cycle of the multinucleate green algae was carried out by considerably deviated cdc2 gene product from other eukaryotes.