藻類でのデンプン分解を調節する仕組みを解明~藻類による持続可能なデンプン生産に期待~

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2025-03-26 東京科学大学

東京科学大学 総合研究院 化学生命科学研究所の今村壮輔特定教授らの研究チームは、藻類におけるデンプン分解を調節する分子メカニズムを解明し、デンプン蓄積量を約1.6倍に向上させることに成功しました。具体的には、デンプン分解に関与するGWDタンパク質の264番目のセリン残基のリン酸化状態が、デンプン分解のスイッチとなることを発見しました。この成果は、藻類を利用したバイオ燃料の増産や環境問題の解決に貢献することが期待されます。

藻類でのデンプン分解を調節する仕組みを解明~藻類による持続可能なデンプン生産に期待~
図1.藻類におけるTORを介したデンプンの分解と合成の調節機構の模式図

<関連情報>

単細胞紅藻におけるα-グルカン、水ジキナーゼを介したデンプン分解を制御するラパマイシンシグナル伝達の標的 Target of rapamycin signaling regulates starch degradation via α-glucan, water dikinase in a unicellular red alga

Sota Komiya, Imran Pancha, Hiroki Shima, Kazuhiro Igarashi, Kan Tanaka, Sousuke Imamura
Plant Physiology  Published:21 March 2025
DOI:https://doi.org/10.1093/plphys/kiaf106

Abstract

Target of rapamycin (TOR) signaling pathways are major regulators of starch accumulation in various eukaryotes. However, the underlying molecular mechanisms of this regulation remain elusive. Here, we report the role of TOR signaling in starch degradation in the unicellular red alga Cyanidioschyzon merolae. Reanalysis of our previously published phosphoproteome data showed that phosphorylation of the serine residue at position 264 of a protein similar to α-Glucan water dikinase (CmGWD), a key regulator of starch degradation, was not increased by rapamycin treatment. In the CmGWD knockout strain, starch content increased and starch phosphorylation decreased, indicating that CmGWD is a functional GWD. CmGWD-dependent starch degradation under dark conditions was alleviated by rapamycin treatment. The overexpression of a phosphomimic CmGWD variant, in which Ser264 was replaced by aspartic acid, or a dephosphomimic CmGWD variant, in which Ser264 was replaced by alanine, resulted in 0.6-fold lower and 1.6-fold higher starch accumulation compared to the wild-type CmGWD-overexpressing strain, respectively. The starch levels corresponded with starch phosphorylation status. Furthermore, the dephosphomimic CmGWD-overexpressing strain accumulated nearly the same amount of starch with or without rapamycin treatment as the rapamycin-treated wild-type CmGWD-overexpressing strain. In contrast, rapamycin treatment did not trigger an increase in starch accumulation in the phosphomimic CmGWD-overexpressing strain. These results indicate that TOR signaling regulates starch degradation in C. merolae by altering the phosphorylation state of Ser264 in CmGWD.

生物工学一般
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