How Embryophytic is the Biosynthesis of Phenylpropanoids and their Derivatives in Streptophyte Algae?
The origin of land plants from algae is a long-standing question in evolutionary biology. It is becoming increasingly clear that many characters that were once assumed to be 'embryophyte specific' can in fact be found in their closest algal relatives, the streptophyte algae. One such case is the phenylpropanoid pathway. While biochemical data indicate that streptophyte algae harbor lignin-like components, the phenylpropanoid core pathway, which serves as the backbone of lignin biosynthesis, has been proposed to have arisen at the base of the land plants. Here we revisit this hypothesis using a wealth of new sequence data from streptophyte algae. Tracing the biochemical pathway towards lignin biogenesis, we show that most of the genes required for phenylpropanoid synthesis and the precursors for lignin production were already present in streptophyte algae. Nevertheless, phylogenetic analyses and protein structure predictions of one of the key enzyme classes in lignin production, cinnamyl alcohol dehydrogenase (CAD), suggest that CADs of streptophyte algae are more similar to sinapyl alcohol dehydrogenases (SADs). This suggests that the end-products of the pathway leading to lignin biosynthesis in streptophyte algae may facilitate the production of lignin-like compounds and defense molecules. We hypothesize that streptophyte algae already possessed the genetic toolkit from which the capacity to produce lignin later evolved in vascular plants.
Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada.
Jan
J
de Vries
Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada.|Population Genetics, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany.
Sophie
S
de Vries
Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada.|Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Toronto, ON, Canada.
Claudio H
CH
Slamovits
Population Genetics, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany.|CEPLAS - Cluster of Excellence in Plant Sciences, Heinrich-Heine University Düsseldorf, Düsseldorf, Germany.
Laura E
LE
Rose
Department of Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada.|Canadian Institute for Advanced Research, Program in Integrated Microbial Biodiversity, Toronto, ON, Canada.
John M
JM
Archibald
D000429:Alcohol Oxidoreductases / Q000378:metabolism; D005075:Biological Evolution; D057946:Charophyceae / Q000378:metabolism*; D054884:Host-Pathogen Interactions; D008031:Lignin / Q000378:metabolism*; D020005:Propanols / Q000378:metabolism*
D020005:Propanols; C439395:1-phenylpropanol; D008031:Lignin; D000429:Alcohol Oxidoreductases; C018656:cinnamyl alcohol dehydrogenase
Charophytes; Lignin; Phenylpropanoids; Plant evolution; Plant–microbe interaction; Secondary metabolism