The horizontal gene transfer of a bacterial polyphenol oxidase may have promoted metabolic innovations in early land plants

LLORENTE B; SOTO G; AYUB ND; MEYER C; RODRÍGUEZ-CONCEPCIÓN M; DE SOUZA FS

Segovia

Encuentro; XI Reunión de Biología Molecular de Plantas; 2012

Centro Nacional de Biotecnología (CSIC-UAM) y Centro de Biotecnología y Genómica de Plantas (CBGP)

The plant polyphenol oxidases (PPOs) are copper oxygen-binding enzymes involved in many physiological functions. They catalyze the hydroxylation and oxidation of phenolic compounds derived from the shikimate and the phenylpropanoid metabolisms. Analysis of the genome sequences of several species spanning the diversity of eukaryotic and prokaryotic life showed that PPOs are highly conserved in land plants but appear to be absent in their sister lineage, the green algae, as well as in other eukaryotes. Phylogenetic and protein domain architecture analyses indicate that plant PPOs are related to a group of bacterial proteins. Particularly, PPO-like proteins from soil bacteria were found to highly resemble plant PPO enzymes. We also established that the catalytic tyrosinase domain of landplant PPOs is more closely related to bacterial tyrosinase domains than to those of green algae and other organisms. Based on these results, we propose that an early land plant ancestor acquired PPO through horizontal gene transfer from bacteria. We further infer that this event allowed new interactions between PPO and the plant shikimate and phenylpropanoid pathways, generating metabolic innovations at the onset of terrestrialization. We are currently performing experiments with different transgenic Arabidopsis (Arabidopsis thaliana) models to test this hypothesis.