Conserved Biochemical Defences Underpin Host Responses to Oomycete Infection in an Early Divergent Land Plant Lineage

While host responses to microbial colonization are extensively explored in evolutionarily young land plant lineages like angiosperms, we know relatively little about plant-pathogen interactions in earlier diverging land plants. We studied the response of the early divergent liverwort Marchantia polymorpha to infection with the oomycete pathogen Phytophthora palmivora. We uncovered a robust response to oomycete colonization in Marchantia that consists of conserved land plant gene families. Macroevolutionary comparisons of host infection responses in Marchantia and the angiosperm Nicotiana benthamiana revealed a shared set of orthologous microbe-responsive genes that include members of the phenylpropanoid pathway. The Marchantia transcription factor MpMyb14 activates the phenylpropanoid (flavonoid) biosynthesis during oomycete infection. MpMyb14 mediates the accumulation of anthocyanin-like pigments and enhanced resistance to infection. The Marchantia response to oomycete infection displays evolutionarily conserved features indicative of an ancestral pathogen deterrence strategy centered on phenylpropanoid-mediated biochemical defenses. The full manuscript can be found here: Carella et al. (2019), Current Biology, https://doi.org/10.1016/j.cub.2019.05.07