title: Chemical control of xylem differentiation by thermospermine, xylemin, and auxin.
abstract: The xylem conducts water and minerals from the root to the shoot and provides mechanical strength to the plant body. The vascular precursor cells of the procambium differentiate to form continuous vascular strands, from which xylem and phloem cells are generated in the proper spatiotemporal pattern. Procambium formation and xylem differentiation are directed by auxin. In angiosperms, thermospermine, a structural isomer of spermine, suppresses xylem differentiation by limiting auxin signalling. However, the process of auxin-inducible xylem differentiation has not been fully elucidated and remains difficult to manipulate. Here, we found that an antagonist of spermidine can act as an inhibitor of thermospermine biosynthesis and results in excessive xylem differentiation, which is a phenocopy of a thermospermine-deficient mutant acaulis5 in Arabidopsis thaliana. We named this compound xylemin owing to its xylem-inducing effect. Application of a combination of xylemin and thermospermine to wild-type seedlings negates the effect of xylemin, whereas co-treatment with xylemin and a synthetic proauxin, which undergoes hydrolysis to release active auxin, has a synergistic inductive effect on xylem differentiation. Thus, xylemin may serve as a useful transformative chemical tool not only for the study of thermospermine function in various plant species but also for the control of xylem induction and woody biomass production.
authors.affiliation: Department of Biological Science, Graduate School of Natural Science and Technology, Okayama University, Tsushimanaka 3-1-1, Okayama 700-8530, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Yoshimoto
authors.affiliation: Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University, Tsushimanaka 3-1-1, Okayama 700-8530, Japan.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Takamura
authors.affiliation: Department of Chemistry, Graduate School of Natural Science and Technology, Okayama University, Tsushimanaka 3-1-1, Okayama 700-8530, Japan.
authors.forename: Isao
authors.initials: I
authors.lastname: Kadota
authors.affiliation: Department of Biological Science, Graduate School of Natural Science and Technology, Okayama University, Tsushimanaka 3-1-1, Okayama 700-8530, Japan.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Motose
authors.affiliation: Department of Biological Science, Graduate School of Natural Science and Technology, Okayama University, Tsushimanaka 3-1-1, Okayama 700-8530, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D017360:Arabidopsis; D029681:Arabidopsis Proteins / Q000096:biosynthesis / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects*; D007210:Indoleacetic Acids / Q000494:pharmacology; D011700:Putrescine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D013095:Spermidine / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013096:Spermine / Q000031:analogs & derivatives* / Q000096:biosynthesis; D052584:Xylem / Q000187:drug effects / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; C000613465:xylemin; C046635:2,4-dichlorophenoxyacetic acid isooctyl ester; D015084:2,4-Dichlorophenoxyacetic Acid; D013096:Spermine; C021097:thermospermine; D013095:Spermidine; D011700:Putrescine