Conservation of Thermospermine Synthase Activity in Vascular and Non-vascular Plants.

Anna Solé-Gil,Jorge Hernández-García,María Pilar López-Gresa,Miguel A Blázquez,Javier Agustí

doi:10.3389/fpls.2019.00663

Abstract

In plants, the only confirmed function for thermospermine is regulating xylem cells maturation. However, genes putatively encoding thermospermine synthases have been identified in the genomes of both vascular and non-vascular plants. Here, we verify the activity of the thermospermine synthase genes and the presence of thermospermine in vascular and non-vascular land plants as well as in the aquatic plant Chlamydomonas reinhardtii. In addition, we provide information about differential content of thermospermine in diverse organs at different developmental stages in some vascular species that suggest that, although the major role of thermospermine in vascular plants is likely to be xylem development, other potential roles in development and/or responses to stress conditions could be associated to such polyamine. In summary, our results in vascular and non-vascular species indicate that the capacity to synthesize thermospermine is conserved throughout the entire plant kingdom.

Highlights

Polyamines are positively charged aliphatic compounds with a widespread presence in all living organisms (Tabor and Tabor, 1984)
The tissue was ground with mortar and pestle and resuspended in 2.5 mL of 5% perchloric acid (PCA) in a 15-mL tube
To check whether the presence of ACL5 orthologs with Tspm synthase (TSPMS) activity correlated with the ability of these species to synthesize Tspm in vivo, we examined the polyamine levels in samples of these plants grown in standard conditions

Summary

Introduction

Polyamines are positively charged aliphatic compounds with a widespread presence in all living organisms (Tabor and Tabor, 1984). The diamine putrescine (Put) and the triamine spermidine (Spd) are the most commonly found polyamines, while the tetra-amine spermine (Spm) is found in yeasts, most animals, seed plants and some bacteria (Pegg and Michael, 2010). It has been proposed that while Spm synthase (SPMS) genes in fungi and plants have likely emerged independently after duplication and neofunctionalization of Spd synthase (SPDS) genes (Minguet et al, 2008), the Tspm synthase (TSPMS) gene in plants was probably acquired through endosymbiosis of a cyanobacterium It is arguable whether such gene originally encoded a TSPMS or an agmatine aminopropyl transferase (Pegg and Michael, 2010; Michael, 2016). The capacity to synthesize different polyamines in a given species is defined by (i) the presence or absence of specific polyamine biosynthetic enzymes and (ii) the degree of specificity

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Conclusion