Putative spermine synthases from Thalassiosira pseudonana and Arabidopsis thaliana synthesize thermospermine rather than spermine

Abstract

Polyamines are involved in many fundamental cellular processes. Common polyamines are putrescine, spermidine and spermine. Spermine is synthesized by transfer of an aminopropyl residue derived from decarboxylated S-adenosylmethionine to spermidine. Thermospermine is an isomer of spermine and assumed to be synthesized by an analogous mechanism. However, none of the recently described spermine synthases was investigated for their possible activity as thermospermine synthases. In this work, putative spermine synthases from the diatom Thalassiosira pseudonana and from Arabidopsis thaliana could be identified as thermospermine synthases. These findings may explain the previous result that two putative spermine synthase genes in Arabidopsis produce completely different phenotypes in knock-out experiments. Likely, part of putative spermine synthases identifiable by sequence comparisons represents in fact thermospermine synthases.

Perturbation of Polyamine Catabolism Can Strongly Affect Root Development and Xylem Differentiation

“…In addition, the importance of PAs in xylem differentiation and cell death has been confirmed by studies of the Arabidopsis mutant of ACAULIS5 (acl5), encoding a thermospermine synthase specifically expressed in the xylem tissues at a precise developmental stage (Knott et al, 2007). This acl5 mutant shows severely reduced secondary growth of the vascular tissue, dramatically altered morphology of the vessel element, and total lack of xylem fibers (Clay and Nelson, 2005).…”

“…In apparent contradiction with our hypothesis about the role played by PA in xylem differentiation and cell death, is the finding that exogenous Spm prolongs xylem element differentiation in xylogenic Zinnia elegans cell cultures, reducing the time of appearance and the rate of tracheal element differentiation as well as the finding that ACL5 controls xylem specification through the prevention of premature cell death in Arabidopsis (Muñ iz et al, 2008). However, this incongruity can be explained by two considerations: (1) contrary to Z. elegans or Arabidopsis plants, PAO expression levels are particularly high in the cytoplasm and cell wall of monocotyledons (Cohen, 1998;Cona et al, 2005) and thus the physiological role of PAs in maize root may depend on the H 2 O 2 released upon PAO-mediated PA oxidation; (2) ACL5, actually being a thermospermine synthase (Knott et al, 2007), may exert its function through a specific effect of thermospermine (Kakehi et al, 2008) that is indeed a poor substrate of ZmPAO (P. Tavladoraki, personal communication).…”

Arabidopsis mutant plants with diverse defects in polyamine metabolism show unequal sensitivity to exogenous cadaverine probably based on their spermine content

“…thermospermine (T-Spm), has been proved in plants by genetic and biochemical approaches (Knott et al 2007;Kakehi et al 2008;Naka et al 2010;Takano et al 2012). The other diamine, cadaverine (Cad), is found in legumes but not in Arabidopsis (Fig.…”

Polyamines in Eukaryotes, Bacteria, and Archaea

“…2) was acquired from the chloroplast cyanobacterial progenitor, consisting of arginine decarboxylase (ADC), which produces agmatine (Agm) from arginine, agmatine iminohydrolase/deiminase (AIH), which produces N-carbamoylputrescine from Agm, and N-carbamoylputrescine amidohydrolase (NCPAH), which produces Put from N-carbamoylputrescine (27)(28)(29)(30). In addition, the same endosymbiotic source appears to have been the origin of the aminopropyltransferase thermospermine synthase (TspmSyn) (25,31), which produces the tetraamine Tspm (Fig. 2), an isomer of Spm, and because of the identical masses of spermine and thermospermine, was originally misidentified as a SpmSyn (32).…”