title: Thermospermine is not a minor polyamine in the plant kingdom.
abstract: Thermospermine is a structural isomer of spermine, which is one of the polyamines studied extensively in the past, and is produced from spermidine by the action of thermospermine synthase encoded by a gene named ACAULIS5 (ACL5) in plants. According to recent genome sequencing analyses, ACL5-like genes are widely distributed throughout the plant kingdom. In Arabidopsis, ACL5 is expressed specifically during xylem formation from procambial cells to differentiating xylem vessels. Loss-of-function mutants of ACL5 display overproliferation of xylem vessels along with severe dwarfism, suggesting that thermospermine plays a role in the repression of xylem differentiation. Studies of suppressor mutants of acl5 that recover the wild-type phenotype in the absence of thermospermine suggest that thermospermine acts on the translation of specific mRNAs containing upstream open reading frames (uORFs). Thermospermine is a novel type of plant growth regulator and may also serve in the control of wood biomass production.
authors.affiliation: Division of Bioscience, Graduate School of Natural Science and Technology, Okayama University, Okayama, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Takano
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Kakehi
authors.forename: Taku
authors.initials: T
authors.lastname: Takahashi
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000235:genetics / Q000502:physiology; D008954:Models, Biological; D016366:Open Reading Frames / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011073:Polyamines / Q000378:metabolism*; D013096:Spermine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: D010940:Plant Proteins; D011073:Polyamines; D013096:Spermine; C021097:thermospermine