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Downregulation of multiple CDK inhibitor ICK / KRP genes upregulates the E2F pathway and increases cell proliferation, and organ and seed sizes in Arabidopsis
Author(s) -
Cheng Yan,
Cao Ling,
Wang Sheng,
Li Yongpeng,
Shi Xianzong,
Liu Han,
Li Lixia,
Zhang Zhengli,
Fowke Larry C.,
Wang Hong,
Zhou Yongming
Publication year - 2013
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12228
Subject(s) - downregulation and upregulation , cyclin dependent kinase , arabidopsis , e2f , cdk inhibitor , cell growth , microbiology and biotechnology , gene , cell cycle , chemistry , cancer research , biology , biochemistry , mutant
Summary 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 / KRP s act as CDK inhibitors under normal physiological conditions in plants. Whereas lower‐order mutants showed no morphological phenotypes, the ick1 ick2 ick6 ick7 and ick1 ick2 ick5 ick6 ick7 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 / KRP s were downregulated, suggesting that to a large extent ICK / KRP s function in plants redundantly in a dosage‐dependent manner. Analyses also revealed increased expression of E2F‐dependent genes, and elevated RBR 1 as well as an increased level of phospho‐ RBB 1 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.