Scots pine aminopropyltransferases shed new light on evolution of the polyamine biosynthesis pathway in seed plants

Abstract

Contrary to previous views, our results demonstrate that SPMS activity is not a novel feature developed solely in the angiosperm lineage of seed plants but also exists as a secondary property in the Scots pine SPDS enzyme. The discovery of bifunctional SPDS from an evolutionarily old conifer reveals the missing link in the evolution of the polyamine biosynthesis pathway. The finding emphasizes the importance of pre-existing secondary functions in the evolution of new enzyme activities via gene duplication. Our results also associate PsACL5 with the development of vascular structures in Scots pine.

Thermospermine Synthase (ACL5) and Diamine Oxidase (DAO) Expression Is Needed for Zygotic Embryogenesis and Vascular Development in Scots Pine

“…We hypothesized that the enzymes in the PA metabolic pathway have acquired different functions during their evolution after the divergence of the seed plant lineages. This hypothesis was supported by our previous findings showing that the Scots pine has a bifunctional SPDS also possessing SPMS activity, which is contrary to angiosperms, which rely on separate enzymes in Spd and Spm biosynthesis (Vuosku et al, 2018). In the present study we are looking for other specific functional characteristics possibly existing in the PA metabolism of Scots pine.…”

“…PA biosynthetic knock-out mutants have indicated that ADC (Urano et al, 2005), SPDS (Imai et al, 2004) and SAMDC (Ge et al, 2006) are essential for embryo development in Arabidopsis (Arabidopsis thaliana L.). Both ADC and SPDS expressed in the mitotic cells of Scots pine zygotic embryos, which supports the essential roles of Put and Spd in basic cell functions (Vuosku et al, 2006;Vuosku et al,2018). In contrast, the Arabidopsis acl5-1 spms-1 double mutant, which contains neither Spm nor T-Spm, is viable and shows no phenotypic change except for the reduced stem growth due to acl5-1 (Imai et al, 2004).…”

“…Diamine Put is the immediate precursor of the tri-and tetra-amines Spd, Spm, and T-Spm which are synthesized by combined actions of S-adenosylmethionine decarboxylase (SAMDC) and the aminopropyltransferases spermidine synthase (SPDS), spermine synthase (SPMS), and thermospermine synthase (TSPMS) (Shao et al, 2012). Both SPDS and SPMS activities can also occur in the same bifunctional enzyme (Vuosku et al, 2018). Put is catabolized by the action of diamine oxidases (DAOs) belonging to the group of copper-containing diamine oxidases (CuAOs) and the higher PAs by the flavoprotein-containing PA oxidases (PAOs) (Bagni and Tassoni, 2001;Bais and Ravishankar, 2002;Marina et al, 2013) (Supplementary Figure S1).…”

“…In plants the complex evolutionary history of the PA biosynthesis pathway includes the transfers of the ADC pathway from the cyanobacterial ancestor of the chloroplast (Illingworth et al, 2003) and TSPMS encoding ACL5 genes from archaea or bacteria . The duplications of SPDS genes have led to the evolution of separate SPDS and SPMS enzymes in flowering plants , whereas a bifunctional progenitor enzyme possessing both SPDS and SPMS activity was preserved in an evolutionary old conifer (Vuosku et al, 2018). All plant species, including Scots pine (Pinus sylvestris L.) and the moss Physcomitrella patens (Hedw.)…”

“…All plant species, including Scots pine (Pinus sylvestris L.) and the moss Physcomitrella patens (Hedw.) Bruch & Schimp possess sequences identified as SPDS or ACL5, but no genomic sequence like the one described for SPMS has been reported from gymnosperms or Physcomitrella so far Rodríguez-Kessler et al, 2010;Vuosku et al, 2018). Although the synthesis of T-Spm likely resembles the formation of Spm (Knott et al, 2007), the TSPMS and SPMS enzymes have different evolutionary origin-TSPMS being more ancient than SPMS in plants.…”