Isolation and characterization of Chlamydomonas autophagy-related mutants in nutrient-deficient conditions
2019
Kajikawa, M. (Kyoto University, Kyoto (Japan). Graduate School of Biostudies) | Yamauchi, M. | Shinkawa, H. | Tanaka, M. | Hatano, K. | Nishimura, Y. | Kato, M. | Fukuzawa, H.
Autophagy is a recycling system for amino acids and carbonand nitrogen (N)-containing compounds. To date, the functional importance of autophagy in microalgae in nutrient-deficient conditions has not been evaluated by using autophagy-defective mutants. Here, we provide evidence which supports the following notions by characterizing an insertional mutant of the autophagy-related gene ATG8, encoding a ubiquitin-like protein necessary for the formation of the autophagosome in the green alga, Chlamydomonas reinhardtii. First, ATG8 is required for maintenance of cell survival and Chl content in N-, sulfur- and phosphate-deficient conditions. Secondly, ATG8 supports the degradation of triacylglycerol and lipid droplets after the resupply of N to cells cultured in N-limiting conditions. Thirdly, ATG8 is also necessary for accumulation of starch in phosphate-deficient conditions. Additionally, autophagy is not essential for maternal inheritance of the organelle genomes in gametogenesis.
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