title: The Arabidopsis eukaryotic translation initiation factor eIF5A-2 regulates root protoxylem development by modulating cytokinin signaling.
abstract: The phytohormone cytokinin regulates various aspects of plant growth and development, including root vascular development. In Arabidopsis thaliana, mutations in the cytokinin signaling components cause misspecification of protoxylem cell files. Auxin antagonizes cytokinin-regulated root protoxylem differentiation by inducing expression of Arabidopsis phosphotransfer protein6 (AHP6), a negative regulator of cytokinin signaling. However, the molecular mechanism of cytokinin-regulated protoxylem differentiation is not fully understood. Here, we show that a mutation in Arabidopsis fumonisin B1-resistant12 (FBR12), which encodes a eukaryotic translation initiation factor 5A, causes defective protoxylem development and reduced sensitivity to cytokinin. FBR12 genetically interacts with the cytokinin receptor cytokinin response1 (CRE1) and downstream AHP genes, as double mutants show enhanced phenotypes. FBR12 forms a protein complex with CRE1 and AHP1, and cytokinin regulates formation of this protein complex. Intriguingly, ahp6 partially suppresses the fbr12 mutant phenotype, and the fbr12 mutation causes increased expression of AHP6, indicating that FBR12 negatively regulates AHP6. Consistent with this, ectopic expression of FBR12 in the CRE1-expressing domain partially rescues defective protoxylem development in fbr12, and overexpression of AHP6 causes an fbr12-like phenotype. These results define a regulatory role of the highly conserved FBR12 in cytokinin-mediated root protoxylem specification.
authors.affiliation: State Key Laboratory of Plant Genomics and National Plant Gene Research Center, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Ren
authors.forename: Qingguo
authors.initials: Q
authors.lastname: Chen
authors.forename: Sulei
authors.initials: S
authors.lastname: Hong
authors.forename: Wenming
authors.initials: W
authors.lastname: Zhao
authors.forename: Jian
authors.initials: J
authors.lastname: Feng
authors.forename: Haizhong
authors.initials: H
authors.lastname: Feng
authors.forename: Jianru
authors.initials: J
authors.lastname: Zuo
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000378:metabolism*; D009154:Mutation; D010448:Peptide Initiation Factors / Q000235:genetics / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development*; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D052584:Xylem / Q000254:growth & development; D000097574:Eukaryotic Translation Initiation Factor 5A
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D010448:Peptide Initiation Factors; D010937:Plant Growth Regulators; D016601:RNA-Binding Proteins; D000097574:Eukaryotic Translation Initiation Factor 5A; C507179:AHP6 protein, Arabidopsis