TY - JOUR
T1 - Target of rapamycin-signaling modulates starch accumulation via glycogenin phosphorylation status in the unicellular red alga Cyanidioschyzon merolae
AU - Pancha, Imran
AU - Shima, Hiroki
AU - Higashitani, Nahoko
AU - Igarashi, Kazuhiko
AU - Higashitani, Atsushi
AU - Tanaka, Kan
AU - Imamura, Sousuke
N1 - Funding Information:
Foundation. IP was supported by a research fellowship from JSPS.
Funding Information:
This study was supported by JSPS KAKENHI (Grants-in-Aid 16F16399 and 17K07438) and the Nagase Science and Technology
Funding Information:
This study was supported by JSPS KAKENHI (Grants-in-Aid 16F16399 and 17K07438) and the Nagase Science and Technology Foundation. IP was supported by a research fellowship from JSPS.
Publisher Copyright:
© 2018 The Authors The Plant Journal © 2018 John Wiley & Sons Ltd
PY - 2019/2/1
Y1 - 2019/2/1
N2 - The target of rapamycin (TOR) signaling pathway is involved in starch accumulation in various eukaryotic organisms; however, the molecular mechanism behind this phenomenon in eukaryotes has not been elucidated. We report a regulatory mechanism of starch accumulation by TOR in the unicellular red alga, Cyanidioschyzon merolae. The starch content in C. merolae after TOR-inactivation by rapamycin, a TOR-specific inhibitor, was increased by approximately 10-fold in comparison with its drug vehicle, dimethyl sulfoxide. However, our previous transcriptome analysis showed that the expression level of genes related to carbohydrate metabolism was unaffected by rapamycin, indicating that starch accumulation is regulated at post-transcriptional levels. In this study, we performed a phosphoproteome analysis using liquid chromatography-tandem mass spectrometry to investigate potential post-transcriptional modifications, and identified 52 proteins as candidate TOR substrates. Among the possible substrates, we focused on the function of CmGLG1, because its phosphorylation at the Ser613 residue was decreased after rapamycin treatment, and overexpression of CmGLG1 resulted in a 4.7-fold higher starch content. CmGLG1 is similar to the priming protein, glycogenin, which is required for the initiation of starch/glycogen synthesis, and a budding yeast complementation assay demonstrated that CmGLG1 can functionally substitute for glycogenin. We found an approximately 60% reduction in the starch content in a phospho-mimicking CmGLG1 overexpression strain, in which Ser613 was substituted with aspartic acid, in comparison with the wild-type CmGLG1 overexpression cells. Our results indicate that TOR modulates starch accumulation by changing the phosphorylation status of the CmGLG1 Ser613 residue in C. merolae.
AB - The target of rapamycin (TOR) signaling pathway is involved in starch accumulation in various eukaryotic organisms; however, the molecular mechanism behind this phenomenon in eukaryotes has not been elucidated. We report a regulatory mechanism of starch accumulation by TOR in the unicellular red alga, Cyanidioschyzon merolae. The starch content in C. merolae after TOR-inactivation by rapamycin, a TOR-specific inhibitor, was increased by approximately 10-fold in comparison with its drug vehicle, dimethyl sulfoxide. However, our previous transcriptome analysis showed that the expression level of genes related to carbohydrate metabolism was unaffected by rapamycin, indicating that starch accumulation is regulated at post-transcriptional levels. In this study, we performed a phosphoproteome analysis using liquid chromatography-tandem mass spectrometry to investigate potential post-transcriptional modifications, and identified 52 proteins as candidate TOR substrates. Among the possible substrates, we focused on the function of CmGLG1, because its phosphorylation at the Ser613 residue was decreased after rapamycin treatment, and overexpression of CmGLG1 resulted in a 4.7-fold higher starch content. CmGLG1 is similar to the priming protein, glycogenin, which is required for the initiation of starch/glycogen synthesis, and a budding yeast complementation assay demonstrated that CmGLG1 can functionally substitute for glycogenin. We found an approximately 60% reduction in the starch content in a phospho-mimicking CmGLG1 overexpression strain, in which Ser613 was substituted with aspartic acid, in comparison with the wild-type CmGLG1 overexpression cells. Our results indicate that TOR modulates starch accumulation by changing the phosphorylation status of the CmGLG1 Ser613 residue in C. merolae.
KW - Cyanidioschyzon merolae
KW - glycogenin
KW - phosphoproteome
KW - red alga
KW - starch
KW - target of rapamycin
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U2 - 10.1111/tpj.14136
DO - 10.1111/tpj.14136
M3 - Article
C2 - 30351485
AN - SCOPUS:85057440772
VL - 97
SP - 485
EP - 499
JO - Plant Journal
JF - Plant Journal
SN - 0960-7412
IS - 3
ER -