期刊
PLANT JOURNAL
卷 75, 期 4, 页码 642-655出版社
WILEY
DOI: 10.1111/tpj.12228
关键词
cell cycle; cell size; cyclin-dependent kinase inhibitor; plant growth; RBR1 and E2F; seed size
资金
- Ministry of Science and Technology of China [2006CB101604, 2011AA10A104]
- National Natural Science Foundation of China [30471097]
- Natural Sciences and Engineering Research Council of Canada
The ICK/KRP cyclin-dependent kinase (CDK) inhibitors are important plant cell cycle factors sharing only limited similarity with the metazoan CIP/KIP family of CDK inhibitors. Little is known about the specific functions of different ICK/KRP genes in planta. In this study, we created double and multiple mutants from five single Arabidopsis ICK/KRP T-DNA mutants, and used a set of 20 lines for the functional investigation of the important gene family. There were gradual increases in CDK activity from single to multiple mutants, indicating that ICK/KRPs act as CDK inhibitors under normal physiological conditions in plants. Whereas lower-order mutants showed no morphological phenotypes, the ick1ick2ick6ick7 and ick1ick2ick5ick6ick7 mutants had a slightly altered leaf shape. The quintuple mutant had larger cotyledons, leaves, petals and seeds than the wild-type control. At the cellular level, the ICK/KRP mutants had more but smaller cells in all the organs examined. These phenotypic effects became more apparent as more ICK/KRPs were downregulated, suggesting that to a large extent ICK/KRPs function in plants redundantly in a dosage-dependent manner. Analyses also revealed increased expression of E2F-dependent genes, and elevated RBR1 as well as an increased level of phospho-RBB1 protein in the quintuple mutant. Thus, downregulation of multiple ICK/KRP genes increases CDK activity, upregulates the E2F pathway and stimulates cell proliferation, resulting in increased cell numbers, and larger organs and seeds.
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