Complex Evolution in the Cellulose Synthase Protein Family: From Core Cell Wall Assembly to Enzymatic and Non-enzymatic Functions in Specialized Metabolism

Specialized metabolites represent a large portion of the plant metabolic repertoire counting thousands in an individual plant. Generating such chemical complexity requires continues evolution of genes encoding proteins producing novel metabolites with selective advantage in a particular environmental niche. Genes with new function in specialized metabolism often arise following duplication of genes involved in primary/core metabolites formed across all species. In the presentation, I will portray several different molecular mechanisms wherein genes of core, primary metabolic pathways were ‘hijacked’, providing a template for the evolution of new enzymatic functions. I will focus on our findings that protein of the cellulose synthase family (i.e. Cellulose Synthase-Like; CSLs) evolved novel activities in different plant families. While we initially identified CSLs associated with triterpenoid saponin biosynthesis, recent results showed that in some plant families such proteins lack enzyme activity and serve as structural elements critical for other pathway proteins function. This example of CSLs and proteins of other classes reported recently, highlight the prevalence and importance of non-catalytic proteins to proper functioning of pathways generating specialized metabolites.