Two Arabidopsis cyclin A3s possess G1 cyclin-like features
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A-type cyclins (CYCAs) are a type of mitotic cyclin and are closely related to cyclin B. Plant CYCAs are classified into three subtypes (CYCA1–CYCA3), among which CYCA3 has been suggested to show a biased expression during the G1-to-S phase. We characterised Arabidopsis CYCA3s (CYCA3;1–CYCA3;4) in terms of expression pattern and protein function. CYCA3;1 and CYCA3;2 transcripts were highly accumulated at the G1/S phase, whereas CYCA3;4 was constantly expressed during the cell cycle. Expressions of CYCA3;1 and CYCA3;2 were observed in actively dividing tissues, such as root and shoot apical meristems and lateral root primordia. Overexpression of CYCA3;1 or CYCA3;2 distorted apical dominance in Arabidopsis, indicating that they have critical functions in shoot meristems. In insect cells, CYCA3;1 formed an active kinase complex with CDKA;1, an orthologue of the yeast Cdc2/Cdc28p, and phosphorylated retinoblastoma-related protein, a key regulator in the transition from the G1 to the S phase. Our results suggest that Arabidopsis CYCA3;1 and CYCA3;2 are distinct members of the G1 cyclin family that play an important role in meristematic tissues.
KeywordsCell cycle Cyclin-dependent kinase Cyclin A RBR protein Arabidopsis thaliana Apical dominance
Cauliflower mosaic virus
Green fluorescent protein
Murashige and Skoog
Open reading frame
Reverse transcription-polymerase chain reaction
We thank Dr. Taku Takahashi (Okayama University), Dr. Tsuyoshi Nakagawa (Shimane University), and Dr. Masami Sekine (Ishikawa Prefectural University) for providing the histone H4 probe, pGWB vectors, and the RBR plasmid, respectively. We also thank the ABRC at Ohio State University for providing the seeds of T-DNA insertion mutants. We are grateful to Dr. Ryoko Ohno (RIBS OKAYAMA) for her help in synchronisation of cultured cells. This work was supported by Grants-in-Aid for Scientific Research on Priority Areas (Grant Nos. 20053013 and 20061021) and a Grant-in-Aid for Scientific Research (B) (Grant No. 19370019) from the Ministry of Education, Culture, Sports, Science and Technology of Japan and by the Program for Promotion of Basic Research Activities for Innovative Biosciences.
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