Center for Gene Research, Nagoya University, Nagoya, Japan; Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan.
Int Rev Cell Mol Biol. 2010;280:281-314. doi: 10.1016/S1937-6448(10)80006-1. Epub 2010 Mar 18.
The unicellular green alga Chlamydomonas reinhardtii has long been used in research on circadian rhythm. Various circadian rhythms in behavior and physiology including phototaxis, chemotaxis, the cell division cycle, UV sensitivity, stickiness to glass (changes in properties of the cell surface), and starch content are observed in this alga. Soon after the isolation of clock mutants in Drosophila melanogaster and Neurospora crassa, clock mutants were also isolated in Chlamydomonas. Whereas genes responsible (clock genes) in Drosophila and Neurospora mutants have been identified and these organisms have become important models for understanding the circadian clock, Chlamydomonas clock genes have not been identified and the molecular basis of the algal clock was unclear until a few years ago. Recently, reverse and forward genetic studies revealed several clock genes in Chlamydomonas. These studies unveiled that the Chlamydomonas clock consists of both original and plant-like components. Further study of the Chlamydomonas circadian clock should provide new insights into the evolution of plant clocks. Furthermore, the identification of its clock genes makes Chlamydomonas a new model for molecular studies of the circadian oscillatory mechanisms in eukaryotes. Its simple cellular architecture may provide significant advantages for a comprehensive understanding of the intracellular temporal organization, especially between the nucleus and chloroplast.
单细胞绿藻莱茵衣藻长期以来一直被用于研究生物钟。在这种藻类中观察到各种生物钟，包括趋光性、趋化性、细胞分裂周期、对紫外线的敏感性、对玻璃的粘性（细胞表面性质的变化）和淀粉含量。在果蝇和粗糙脉孢菌中分离出生物钟突变体后不久，也在衣藻中分离出生物钟突变体。虽然在果蝇和粗糙脉孢菌突变体中鉴定出了负责的基因（生物钟基因），这些生物已成为理解生物钟的重要模型，但衣藻生物钟基因尚未被鉴定，藻类生物钟的分子基础直到几年前还不清楚。最近，反向和正向遗传学研究揭示了衣藻中的几个生物钟基因。这些研究表明，衣藻生物钟由原始和植物样成分组成。对衣藻生物钟的进一步研究应该为植物钟的进化提供新的见解。此外，其生物钟基因的鉴定使衣藻成为研究真核生物生物钟振荡机制的分子研究的新模式。其简单的细胞结构可能为全面了解细胞内的时间组织提供显著优势，特别是在细胞核和叶绿体之间。
