title: The dwarf phenotype of the Arabidopsis acl5 mutant is suppressed by a mutation in an upstream ORF of a bHLH gene.
abstract: Loss-of-function mutants of the Arabidopsis thaliana ACAULIS 5 (ACL5) gene, which encodes spermine synthase, exhibit a severe dwarf phenotype. To elucidate the ACL5-mediated regulatory pathways of stem internode elongation, we isolated four suppressor of acaulis (sac) mutants that reverse the acl5 dwarf phenotype. Because these mutants do not rescue the dwarfism of known phytohormone-related mutants, the SAC genes appear to act specifically on the ACL5 pathways. We identify the gene responsible for the dominant sac51-d mutant, which almost completely suppresses the acl5 phenotype. sac51-d disrupts a short upstream open reading frame (uORF) of SAC51, which encodes a bHLH-type transcription factor. Our results indicate that premature termination of the uORF in sac51-d results in an increase in its own transcript level, probably as a result of an increased translation of the main ORF. We suggest a model in which ACL5 plays a role in the translational activation of SAC51, which may lead to the expression of a subset of genes required for stem elongation.
authors.affiliation: Division of Bioscience, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Imai
authors.forename: Yoshie
authors.initials: Y
authors.lastname: Hanzawa
authors.forename: Mio
authors.initials: M
authors.lastname: Komura
authors.forename: Kotaro T
authors.initials: KT
authors.lastname: Yamamoto
authors.forename: Yoshibumi
authors.initials: Y
authors.lastname: Komeda
authors.forename: Taku
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D017353:Gene Deletion; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D008856:Microscopy, Fluorescence / Q000379:methods; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics*; D016366:Open Reading Frames / Q000235:genetics*; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013097:Spermine Synthase / Q000235:genetics / Q000378:metabolism; D013489:Suppression, Genetic
chemical_list: D029681:Arabidopsis Proteins; D051792:Basic Helix-Loop-Helix Proteins; D005966:Glucuronidase; D010937:Plant Growth Regulators; D011993:Recombinant Fusion Proteins; D013097:Spermine Synthase; C414439:ACAULIS5 protein, Arabidopsis; C515850:SAC51 protein, Arabidopsis