Periderm differentiation: a cellular and molecular approach to cork oak

Key message This compilation is focused on the role of cork oak periderm, a protective layer with unique physical and chemical traits for the cork industry, highlighting the recent periderm-specific genomic resources available. Cork oak is a unique species with the ability to produce a continuous and renewable cork throughout its lifespan. Periderm is a protective tissue composed of the phellem, phellogen, and phelloderm that replaces the epidermis. Phellem or “cork”, the outermost layer, is produced by the original phellogen, a secondary meristem originated from the dedifferentiation of mature parenchyma cells. The formation and differentiation of periderm have been widely studied demonstrating the importance of fatty acid biosynthesis, phenylpropanoid, and metabolism of suberin, a complex glycerol-based polymer and the principal component of phellem. The contributions of several areas reveal new clues concerning the molecular mechanisms behind periderm differentiation. However, the whole process is still poorly understood. In this review, we compile information regarding the cellular structure and molecular basis, including the regulatory network of periderm formation and differentiation, focusing on the cork oak. The cork quality and its genetic and epigenetic mechanisms are also explored, highlighting the importance of molecular regulation in such economically important species. An increased understanding of the all periderm differentiation process may serve as a basis for future studies on functional genomics with an impact on fundamental science and on the forest industry for the production of high-quality cork.