Genomes of Poaceae relatives reveal key metabolic innovations preceding the evolution of grasses

The grass family (Poaceae) has immense economic and ecological importance and exhibits distinctive metabolic traits, including dual starch and lignin biosynthetic pathways. We sequenced the genomes of Pharus, Joinvillea, Ecdeiocolea, and Typha species to investigate when and how these metabolic innovations evolved relative to the origin of the grass family. The rho whole-genome duplication (ρWGD) within the lineage that led to the last common ancestor of all grasses contributed to the gene family expansions underlying cytosolic starch biosynthesis, whereas an earlier tandem duplication of phenylalanine ammonia lyase (PAL) gave rise to phenylalanine/tyrosine ammonia lyase (PTAL), which is responsible for the dual lignin biosynthesis. Integrated biochemical, functional, and structural studies, guided by phylogenomic analyses, further revealed the molecular basis of key metabolic innovations predating the evolution of grasses.