Glutathione mediated cell cycle regulation inChlamydomonas reinhardtii

• Main Authors: Chun-HanChen, 陳君函
• Other Authors: Su-Chiung Fang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/31756039397675080721

碩士 === 國立成功大學 === 熱帶植物科學研究所 === 101 === Regulation of the cell cycle is essential to drive cell proliferation. Chlamydomonas reinhardtii is a unicellular green alga that utilizes a specialized cell cycle program, multiple-fission, for cell division. In this study, smt15-1 mutant was isolated as a cell size mutant that had defective putative sulfate transporter and aberrant cell cycle program. smt15-1 had increased amount of total glutathione and failed to fully acclimate to sulfur starvation condition. Previous studies have suggested that the GSH-mediated sub-cellular reduction/oxidation (redox) homeostasis is important for the cell cycle control in eukaryotic cells. We also observed the total glutathione content oscillated during the mitotic cell cycle in Chlamydomonas. In addition, smt15-1 mutant accumulated more glutathione than wild-type strain at late G1 and S/M phases in synchronized culture. Base on these result, we hypothesized that GSH-mediated cellular redox regulation is important for cell-cycle control in Chlamydomonas. Indeed, increased cellular reducing state by adding N-acetyl-L-cysteine (NAC) caused a delay in entry into mitosis in synchronized cultures. Additionally, depleted GSH using diethylmaleate (Et2Mal, glutathione-depleting reagent) resulted in aberrant entry into the cell cycle. Decreasing GSH levels in the smt15-1 mutant using Et2Mal under sulfur-depleted condition led to a slight increase in induction of an arylsulfatase (ARS) mRNA, indicating that accumulation of GSH in smt15-1 under sulfur-depleted condition attenuated sulfur acclimation (SAC) response. Furthermore, increasing total glutathione content by overexpressing the glutathione synthetase (GSH2) led to increase in cell division number and decrease in daughter cell size, which was reminiscent to smt15-1 mutant. In conclusion, SMT15 modulates intracellular glutathione that affects SAC response and cell division in Chlamydomonas.