A team of researchers led by Hugues Renault has deciphered a fundamental element of the evolution of land plants: cinnamate 4-hydroxylase (C4H). This enzyme is essential for the production of phenylpropanoids, a family of metabolites closely linked to the adaptation of plants to life outside water. Published in The EMBO Journal, this study reveals that C4H activity emerged with the CYP73 gene family in a common ancestor of embryophytes, marking a crucial step in plant evolution.
The researchers identified conserved residues within CYP73 proteins, including a critical arginine, which have supported C4H activity since the earliest stages of its evolution. They then demonstrated that C4H deficiency, achieved by inactivating CYP73 genes or treatment with a specific inhibitor, leads to a shortage of phenylpropanoids and abnormal development in three bryophyte species: the moss Physcomitrium patens, the liverwort Marchantia polymorpha, and the hornwort Anthoceros agrestis. These harmful effects were reversed in the moss by the exogenous supply of p-coumaric acid, the product of the C4H enzyme.
This discovery shows that the emergence of the CYP73 gene family was a foundational event in the development of the phenylpropanoid pathway in plants and highlights the central role of the C4H enzyme in the biology of embryophytes. These results provide new insights into the evolution of land plants and the mechanisms that enabled their adaptation to terrestrial environments.
