title: Down-regulation of multiple CDK inhibitor ICK/KRP genes promotes cell proliferation, callus induction and plant regeneration in Arabidopsis.
abstract: The ICK/KRP cyclin-dependent kinase (CDK) inhibitors are important plant cell cycle regulators sharing only limited similarity with the metazoan CIP/KIP family of CDK inhibitors. Information is still limited regarding the specific functions of different ICK/KRP genes in planta. We have shown previously that down-regulation of multiple CDK inhibitor ICK/KRP genes up-regulates the E2F pathway and increases cell proliferation, and organ and seed sizes in Arabidopsis. In this study, we observed that the quintuple ick1/2/5/6/7 mutant had more cells in the cortical layer of the root apical meristem (RAM) than the wild type (Wt) while its RAM length was similar to that of the Wt, suggesting a faster cell cycle rate in the quintuple mutant. We further investigated the effects of down-regulating ICK genes on tissue culture responses. The cotyledon explants of ick1/2/5/6/7 could form callus efficiently in the absence of cytokinin and also required a lower concentration of 2,4-D for callus induction compared to the Wt plants, suggesting increased competence for callus induction in the mutant. In addition, the quintuple ick mutant showed enhanced abilities to regenerate shoots and roots, suggesting that increased competence to enter the cell cycle in the quintuple mutant might make it possible for more cells to become proliferative and be utilized to form shoots or roots. These findings indicate that CDK activity is a major factor underlying callus induction and increased cell proliferation can enhance in vitro organogenesis.
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Cheng
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Han
authors.initials: H
authors.lastname: Liu
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China ; Department of Biochemistry, University of Saskatchewan, Saskatoon SK, Canada.
authors.forename: Ling
authors.initials: L
authors.lastname: Cao
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon SK, Canada.
authors.forename: Sheng
authors.initials: S
authors.lastname: Wang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Yongpeng
authors.initials: Y
authors.lastname: Li
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.affiliation: National Key Laboratory of Crop Genetic Improvement, College of Plant Science and Technology, Huazhong Agricultural University Wuhan, China.
authors.forename: Yongming
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Department of Biochemistry, University of Saskatchewan, Saskatoon SK, Canada.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
keywords: Arabidopsis thanliana; CDK inhibitor; ICK/KRP; callus induction; cell cycle; cell proliferation; cyclin-dependent kinase; plant regeneration