Peeling off the Poplar Cuticle, from Biochemistry to Defensive Roles

Plant cuticles are complex mixtures of hydrophobic components, composed of monomeric cuticular waxes and a lipidic polymer of cutin. Underground organs and specific tissues such as stem bark form another related lipidic polymer known as suberin. The quantity and composition of these protective layers can vary between different tissues and under different conditions, likely to meet different physiological and ecological roles. In poplar, the study of cuticles using molecular tools is an emerging field owing to the recent abundance of genomic resources combined with the large variation in composition detected in the genus. Compared with traditionally used model systems such as Arabidopsis, maize or barley, poplar poses unique advantages to understanding wax processes in a perennial, deciduous, and woody species. This chapter reviews the poplar cuticle, first describing its chemical composition, then outlining the major biosynthetic pathways. We follow with a review of the role of waxes in plant defense, summarizing current knowledge on their role in mediating biotic and abiotic interactions in poplar. Finally, we suggest a simple method to mine available datasets with the goal of predicting genes to further characterize in Populus.