Themospermine is a structural isomer of spermine and is present in some bacteria and most of plants. An Arabidopsis mutant, acaulis5 (acl5), that is defective in the biosynthesis of thermospermine displays excessive proliferation of xylem vessels with dwarfed growth. Recent studies using acl5 and its suppressor mutants that recover the growth without thermospermine have revealed that thermospermine plays a key role in the negative control of the proliferation of xylem vessels through enhancing translation of specific mRNAs that contain a conserved upstream open-reading-frame (uORF) in the 5' leader region.
Keywords: Acaulis5; Arabidopsis; Thermospermine; Xylem; mRNA translation; uORF.