Downregulation of multiple CDK inhibitor ICK/KRP genes upregulates the E2F pathway and increases cell proliferation, and organ and seed sizes in Arabidopsis
Downregulation of multiple CDK inhibitor ICK/KRP genes upregulates the E2F pathway and increases cell proliferation, and organ and seed sizes in Arabidopsis
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DOI：
10.1111/tpj.12228
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发表时间：
2013-08-01
期刊：
影响因子：
7.2
通讯作者：
Zhou, Yongming
中科院分区：
文献类型：
--
作者：
Cheng, Yan;Cao, Ling;Zhou, Yongming
ICK/KRP细胞周期蛋白依赖性激酶（cyclin-dependent kinase，CDK）抑制剂是重要的植物细胞周期因子，与后生动物CIP/KIP家族的CDK抑制剂仅有有限的相似性。目前对植物中不同ICK/KRP基因的功能还知之甚少。在本研究中，我们从5个拟南芥ICK/KRP T-DNA单突变体中构建了双重和多重突变体，并使用了一组20个株系来研究该重要基因家族的功能。从单个突变体到多个突变体，CDK活性逐渐增加，表明ICK/KRP在植物正常生理条件下充当CDK抑制剂。虽然低级突变体没有表现出形态表型，但ick 1 ick 2 ick 6 ick 7和ick 1 ick 2 ick 5ick 6 ick 7突变体的叶子形状略有改变。五倍体突变体比野生型对照具有更大的子叶、叶片、花瓣和种子。在细胞水平上，ICK/KRP突变体在检查的所有器官中具有更多但更小的细胞。随着更多的ICK/KRPs被下调，这些表型效应变得更加明显，这表明在很大程度上ICK/KRPs以剂量依赖性方式在植物中冗余地发挥作用。分析还揭示了E2 F依赖性基因的表达增加，RBR 1升高以及五倍体突变体中磷酸-RBB 1蛋白水平增加。因此，多个ICK/KRP基因的下调增加CDK活性，上调E2 F途径并刺激细胞增殖，导致细胞数量增加，器官和种子更大。
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.