title: Novel functions of plant cyclin-dependent kinase inhibitors, ICK1/KRP1, can act non-cell-autonomously and inhibit entry into mitosis.
abstract: In animals, cyclin-dependent kinase inhibitors (CKIs) are important regulators of cell cycle progression. Recently, putative CKIs were also identified in plants, and in previous studies, Arabidopsis thaliana plants misexpressing CKIs were found to have reduced endoreplication levels and decreased numbers of cells consistent with a function of CKIs in blocking the G1-S cell cycle transition. Here, we demonstrate that at least one inhibitor from Arabidopsis, ICK1/KRP1, can also block entry into mitosis but allows S-phase progression causing endoreplication. Our data suggest that plant CKIs act in a concentration-dependent manner and have an important function in cell proliferation as well as in cell cycle exit and in turning from a mitotic to an endoreplicating cell cycle mode. Endoreplication is usually associated with terminal differentiation; we observed, however, that cell fate specification proceeded independently from ICK1/KRP1-induced endoreplication. Strikingly, we found that endoreplicated cells were able to reenter mitosis, emphasizing the high degree of flexibility of plant cells during development. Moreover, we show that in contrast with animal CDK inhibitors, ICK1/KRP1 can move between cells. On the one hand, this challenges plant cell cycle control with keeping CKIs locally controlled, and on the other hand this provides a possibility of linking cell cycle control in single cells with the supracellular organization of a tissue or an organ.
authors.affiliation: Unigruppe am Max-Planck-Institut für Züchtungsforschung, Lehrstuhl für Botanik III, Max-Delbrück-Laboratorium, 50829 Köln, Germany.
authors.forename: Christina
authors.initials: C
authors.lastname: Weinl
authors.forename: Sebastian
authors.initials: S
authors.lastname: Marquardt
authors.forename: Suzanne J H
authors.initials: SJ
authors.lastname: Kuijt
authors.forename: Moritz K
authors.initials: MK
authors.lastname: Nowack
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Jakoby
authors.forename: Martin
authors.initials: M
authors.lastname: Hülskamp
authors.forename: Arp
authors.initials: A
authors.lastname: Schnittger
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002450:Cell Communication / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D049108:Cell Enlargement; D019070:Cell Lineage / Q000235:genetics; D049109:Cell Proliferation; D050756:Cyclin-Dependent Kinase Inhibitor Proteins / Q000235:genetics / Q000378:metabolism*; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics*; D018816:Genes, cdc / Q000502:physiology*; D008938:Mitosis / Q000235:genetics*; D021381:Protein Transport / Q000235:genetics; D016196:S Phase / Q000235:genetics
chemical_list: D029681:Arabidopsis Proteins; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; C114853:ICK1 protein, Arabidopsis; D018844:Cyclin-Dependent Kinases