Functional conservation in the SIAMESE-RELATED family of cyclin-dependent kinase inhibitors in land plants

Narender Kumar, Hirofumi Harashima, Shweta Kalve, Jonathan Bramsiepe, Kai Wang, Bulelani L. Sizani, Laura L. Bertrand, Matthew C. Johnson, Christopher Faulk, Renee Dale, L. Alice Simmons, Michelle L. Churchman, Keiko Sugimoto, Naohiro Kato, Maheshi Dasanayake, Gerrit Beemster, Arp Schnittger, John C. Larkin

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


The best-characterized members of the plant-specific SIAMESE-RELATED (SMR) family of cyclin-dependent kinase inhibitors regulate the transition from the mitotic cell cycle to endoreplication, also known as endoreduplication, an altered version of the cell cycle in which DNA is replicated without cell division. Some other family members are implicated in cell cycle responses to biotic and abiotic stresses. However, the functions of most SMRs remain unknown, and the specific cyclin- dependent kinase complexes inhibited by SMRs are unclear. Here, we demonstrate that a diverse group of SMRs, including an SMR from the bryophyte Physcomitrella patens, can complement an Arabidopsis thaliana siamese (sim) mutant and that both Arabidopsis SIM and P. patens SMR can inhibit CDK activity in vitro. Furthermore, we show that Arabidopsis SIM can bind to and inhibit both CDKA;1 and CDKB1;1. Finally, we show that SMR2 acts to restrict cell proliferation during leaf growth in Arabidopsis and that SIM, SMR1/LGO, and SMR2 play overlapping roles in controlling the transition from cell division to endoreplication during leaf development. These results indicate that differences in SMR function in plant growth and development are primarily due to differences in transcriptional and posttranscriptional regulation, rather than to differences in fundamental biochemical function.

Original languageEnglish (US)
Pages (from-to)3065-3080
Number of pages16
JournalPlant Cell
Issue number11
StatePublished - Nov 2015

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© 2015 American Society of Plant Biologists. All rights reserved.

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