title: CYTOKININ OXIDASE/DEHYDROGENASE4 Integrates Cytokinin and Auxin Signaling to Control Rice Crown Root Formation.
abstract: Crown roots constitute the majority of the rice (Oryza sativa) root system and play an important role in rice growth and development. However, the molecular mechanism of crown root formation in rice is not well understood. Here, we characterized a rice dominant mutant, root enhancer1 (ren1-D), which was observed to exhibit a more robust root system, increased crown root number, and reduced plant height. Molecular and genetic analyses revealed that these phenotypes are caused by the activation of a cytokinin oxidase/dehydrogenase (CKX) family gene, OsCKX4. Subcellular localization demonstrated that OsCKX4 is a cytosolic isoform of CKX. OsCKX4 is predominantly expressed in leaf blades and roots. It is the dominant CKX, preferentially expressed in the shoot base where crown root primordia are produced, underlining its role in root initiation. OsCKX4 is induced by exogenous auxin and cytokinin in the roots. Furthermore, one-hybrid assays revealed that OsCKX4 is a direct binding target of both the auxin response factor OsARF25 and the cytokinin response regulators OsRR2 and OsRR3. Overexpression and RNA interference of OsCKX4 confirmed that OsCKX4 plays a positive role in crown root formation. Moreover, expression analysis revealed a significant alteration in the expression of auxin-related genes in the ren1-D mutants, indicating that the OsCKX4 mediates crown root development by integrating the interaction between cytokinin and auxin. Transgenic plants harboring OsCKX4 under the control of the root-specific promoter RCc3 displayed enhanced root development without affecting their shoot parts, suggesting that this strategy could be a powerful tool in rice root engineering.
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.).
authors.forename: Shaopei
authors.initials: S
authors.lastname: Gao
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.).
authors.forename: Jun
authors.initials: J
authors.lastname: Fang
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.).
authors.forename: Fan
authors.initials: F
authors.lastname: Xu
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.).
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.).
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Sun
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.).
authors.forename: Jinfang
authors.initials: J
authors.lastname: Chu
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.).
authors.forename: Baodong
authors.initials: B
authors.lastname: Cai
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.).
authors.forename: Yuqi
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Key Laboratory of Cell Proliferation and Regulation Biology of the Ministry of Education, College of Life Sciences, Beijing Normal University, Beijing 100875, China (S.G.);State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China (S.G., J.F., F.X., W.W., X.S., J.C., C.C.); andKey Laboratory of Analytical Chemistry for Biology and Medicine of the Ministry of Education, Department of Chemistry, Wuhan University, Wuhan 430072, China (B.C., Y.F.) ccchu@genetics.ac.cn.
authors.forename: Chengcai
authors.initials: C
authors.lastname: Chu