Genomes of Poaceae Sisters Reveal Key Metabolic Innovations Preceding the Emergence of Grasses

The grass family (Poaceae, Poales) holds immense economic and ecological significance, exhibiting unique metabolic traits, including dual starch and lignin biosynthetic pathways. To investigate when and how the metabolic innovations known in grasses evolved, we sequenced the genomes of a non-core grass, Pharus latifolius, the non-grass graminids, Joinvillea ascendens and Ecdeiocolea monostachya, representing the sister clade to Poaceae, and Typha latifolia, representing the sister clade to the remaining Poales. The rho whole genome duplication (ρWGD) in the ancestral lineage for 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) responsible for the dual lignin biosynthesis. Two mutations were sufficient to expand ancestral PAL function into PTAL. The integrated genomic and biochemical analyses of grass relatives in Poales revealed the evolutionary and molecular basis of key metabolic innovations of grasses. ### Competing Interest Statement Y.T-K, B.M., and H.A.M. have a pending patent application related to the two mutations that can convert PAL enzymes into PTAL enzymes. The other authors declare that they have no competing interests related to this work.