Function of the HYDROXYCINNAMOYL-CoA:SHIKIMATE HYDROXYCINNAMOYL TRANSFERASE is evolutionarily conserved in embryophytes

Abstract

The plant phenylpropanoid pathway generates a major class of specialized metabolites and precursors of essential extracellular polymers that initially appeared upon plant terrestrialization. Despite its evolutionary significance, little is known about the complexity and function of this major metabolic pathway in extant bryophytes, the ancestors of which were the first land plants. Here, we report that the HYDROXYCINNAMOYL-CoA:SHIKIMATE HYDROXYCINNAMOYL TRANSFERASE (HCT) gene, which plays a critical function in the phenylpropanoid pathway during seed plant development, is functionally conserved in Physcomitrium (Physcomitrella) patens, in the moss lineage of bryophytes. Phylogenetic analysis indicates that bona fide HCT function emerged in the progenitor of embryophytes. In vitro enzyme assays, moss phenolic pathway reconstitution in yeast and in planta gene inactivation coupled to targeted metabolic profiling collectively indicate that P. patens HCT (PpHCT), similar to tracheophyte HCT orthologs, uses shikimate as a native acyl acceptor to produce a p-coumaroyl-5-O-shikimate intermediate. Phenotypic and metabolic analyses of loss-of-function mutants show that PpHCT is necessary for the production of caffeate derivatives, including previously reported caffeoyl-threonate esters, and for the formation of an intact cuticle. Deep conservation of HCT function in embryophytes is further suggested by the ability of HCT genes from P. patens and the liverwort Marchantia polymorpha to complement an Arabidopsis thaliana CRISPR/Cas9 hct mutant, and by the presence of phenolic esters of shikimate in representative species of the three major bryophyte lineages.One sentence summaryMultidisciplinary study of the HYDROXYCINNAMOYL-CoA:SHIKIMATE HYDROXYCINNAMOYL TRANSFERASE (HCT) gene in Physcomitrium (Physcomitrella) patens points to its functional conservation in embryophytes.

The evolution of the phenylpropanoid pathway entailed pronounced radiations and divergences of enzyme families

“…Recently, Kriegshauser et al. (2021) reported on the functional conservation of the HCT homologs found in bryophytes with those of seed plants.…”

NO GAMETOPHORES 2 Is a Novel Regulator of the 2D to 3D Growth Transition in the Moss Physcomitrella patens

“…28 It has been shown, however, that the transfer of alcohols or amines to p-coumaroyl CoA by P. patens HCT (PpNOG2) produces p-coumaroyl threonate rather than the p-coumaroyl shikimate ll produced by HCT in Arabidopsis. 29 Interestingly, both the formation of p-coumaroyl threonate by PpNOG2 and subsequent modification by PpCYP98A3 occur in an ascorbic acid pathway, suggesting that these enzymes were co-opted into the lignin biosynthesis pathway after the divergence of bryophytes and vascular plants.…”

The evolution of the phenylpropanoid pathway entailed pronounced radiations and divergences of enzyme families

“…Despite the origin of CSE in the common ancestor of land plants and a clear CSE ortholog in Physcomitrium patens (3c19_14430V3.1.p), the substrate of CSE, caffeoyl-5- O -shikimate, was not detected in crude extracts of the moss (Renault et al, 2017a). The HCT-based reaction leading to caffeoyl-CoA has been confirmed in vitro using moss HCT (Kriegshauser et al 2021). Hence, the CSE homologs of Physcomitrium patens may have another function.…”