Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

CO2-Responsive CCT Protein (CRCT) is a transcription factor that positively regulates the expression of starch synthesis-related genes in the vegetative organs of rice. CRCT interacts with 14-3-3 proteins. Yeast two-hybrid analysis showed that the CRCT with the S217A mutation was unable to interact with CRCT. This mutated CRCT was introduced into the CRCT knockout rice. The transcript of CRCT-S217A was detected significantly by qRT-PCR, but not by immunoblotting. Nevertheless, starch accumulation and the expression of starch synthesis-related genes in the leaf sheath of the transformants were higher than those of the CRCT knockout line. These results suggest the possibility that 14-3-3 proteins may stabilize CRCT through their interaction, while free unstable CRCT can promote starch synthesis. CRCT was shown to be highly expressed in the vascular bundle and is hypothesized to move to the starch-accumulating storage parenchyma cells in leaf sheaths. To investigate this hypothesis, we generated transgenic lines expressing CRCT ectopically in the CRCT knockout line background. Transgenic lines expressing CRCT using Sucrose transpor1 promoter, known to express specifically in vascular tissues, and the Chlorophyll a/b binding protein promoter, known to express highly in photosynthetic tissues, showed recovered starch accumulation in the leaf sheath. These results suggest that CRCT can move from an unspecified cell to storage parenchyma cells via the vascular bundle to regulate starch synthesis. This study can provide new insight into the regulation mechanism of starch biosynthesis in the vegetative organs.

DOI： 10.1016/j.plantsci.2026.113157

PubMed

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Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

Abstract

CO2-Responsive CCT Protein (CRCT) is a transcription factor that regulates the expression of starch synthesis-related genes, and consequently starch content in the vegetative organs of rice. Two CRCT homologues, AtCRCT1 and AtCRCT2, were identified in the genome of Arabidopsis thaliana. AtCRCT1 and AtCRCT2 were expressed in most organs of the plant, and AtCRCT2 in particular was expressed in their vascular bundles. The expression of these genes was markedly upregulated by sucrose treatment and tended to increase under elevated CO2 condition. The overexpression or knockout of these genes did not have a notable effect on the growth of Arabidopsis. On the other hand, the expression of some starch synthesis-related genes, such as ADP-glucose pyrophosphorylase large subunit3 (AtAPL3) and glucose 6-phosphate/Pi transporter2 (AtGPT2) was significantly upregulated in the overexpression lines. Accordingly, the expression of AtAPL3 and AtGPT2 in the double knockout line was significantly lower than that in wild-type (Col-0) under sucrose treatment. In addition, the starch content of the double knockout line at the end of the night was slightly lower than that of Col-0. Yeast two-hybrid and BiFC analyses demonstrated that both AtCRCT1 and AtCRCT2 interact with Growth Regulation Factor 7, a 14-3-3 protein. These results suggest that AtCRCT1 and AtCRCT2 have similar molecular and physiological functions to CRCT in rice and regulate the expression of some starch synthesis-related genes. However, their effects are limited and cannot markedly affect starch content, unlike CRCT in rice.

DOI： 10.1093/pcp/pcag011

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/1343943x.2024.2344833

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/1343943x.2023.2233161

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

Abstract

CO₂‐responsive CCT protein (CRCT) is a positive regulator of starch synthesis–related genes such as ADP‐glucose pyrophosphorylase large subunit 1 and starch branching enzyme I particularly in the leaf sheath of rice (Oryza sativa L.). The promoter GUS analysis revealed that CRCT expressed exclusively in the vascular bundle, whereas starch synthesis–related genes were expressed in different sites such as mesophyll cell and starch storage parenchyma cell. However, the chromatin immunoprecipitation (ChIP) using a FLAG‐CRCT overexpression line and subsequent qPCR analyses showed that the 5′‐flanking regions of these starch synthesis–related genes tended to be enriched by ChIP, suggesting that CRCT can bind to the promoter regions of these genes. The monomer of CRCT is 34.2 kDa; however, CRCT was detected at 270 kDa via gel filtration chromatography, suggesting that CRCT forms a complex in vivo. Immunoprecipitation and subsequent MS analysis pulled down several 14‐3‐3‐like proteins. A yeast two‐hybrid analysis and bimolecular fluorescence complementation assays confirmed the interaction between CRCT and 14‐3‐3‐like proteins. Although there is an inconsistency in the place of expression, this study provides important findings regarding the molecular function of CRCT to control the expression of key starch synthesis–related genes.

DOI： 10.1111/pce.14084

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/pce.14084

J-GLOBAL

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J-GLOBAL

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J-GLOBAL

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Authorship：Lead author   Language：Japanese   Publishing type：Meeting report  

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Event date： 2026.3.28 - 2026.3.29

Language：Japanese  

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Event date： 2026.3.28 - 2026.3.29

Language：Japanese  

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Event date： 2025.9.21 - 2025.9.22

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2025.5.19 - 2025.5.21

Language：English   Presentation type：Poster presentation  

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Event date： 2025.3.28 - 2025.3.29

Language：Japanese   Presentation type：Oral presentation (general)  

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