title: Thermospermine suppresses auxin-inducible xylem differentiation in Arabidopsis thaliana.
abstract: Thermospermine, a structural isomer of spermine, is synthesized by a thermospermine synthase designated ACAULIS5 (ACL5). Thermospermine-deficient acl5 mutant of Arabidopsis thaliana shows severe dwarfism and excessive xylem differentiation. By screening for compounds that affect xylem differentiation in the acl5 mutant, we identified auxin analogs that remarkably enhanced xylem vessel differentiation in the acl5 mutant but not in the wild type. The xylem-inducing effect of auxin analogs was clearly suppressed by thermospermine, indicating that auxin-inducible xylem differentiation is normally limited by thermospermine. Here, we further characterized xylem-inducing effect of auxin analogs in various organs. Auxin analogs promoted protoxylem differentiation in roots and cotyledons in the acl5 mutant. Our results indicate that the opposite action between thermospermine and auxin in xylem differentiation is common in different organs and also suggest that thermospermine might be required for the suppression of protoxylem differentiation.
authors: Division of Bioscience, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
authors: Kaori
authors: K
authors: Yoshimoto
authors: Yoshiteru
authors: Y
authors: Noutoshi
authors: Ken-ichiro
authors: K
authors: Hayashi
authors: Ken
authors: K
authors: Shirasu
authors: Taku
authors: T
authors: Takahashi
authors: Hiroyasu
authors: H
authors: Motose
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000737:chemistry / Q000494:pharmacology; D017360:Arabidopsis / Q000166:cytology* / Q000187:drug effects*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002454:Cell Differentiation / Q000187:drug effects*; D007210:Indoleacetic Acids / Q000737:chemistry / Q000494:pharmacology*; D009154:Mutation / Q000235:genetics; D013096:Spermine / Q000031:analogs & derivatives* / Q000494:pharmacology; D052584:Xylem / Q000166:cytology* / Q000187:drug effects*
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D015084:2,4-Dichlorophenoxyacetic Acid; D013096:Spermine; C021097:thermospermine