Abstract text: The seed coat and leaf epidermis form specialized lipid-based barriers composed of the biopolyesters cutin and suberin. These extracellular matrices are essential for plant survival, regulating water permeability and protecting against environmental stress. In seeds, these barriers contribute to dormancy, longevity, and controlled water uptake during germination, whereas in leaves they prevent excessive water loss and enhance resistance to pathogens and abiotic stress. While major progress has been made in identifying the metabolic pathways producing cutin and suberin monomers, the enzymatic mechanisms responsible for assembling these polymers in the apoplast and ensuring their tissue-specific deposition remain largely unknown. Here, I present evidence that members of the GDSL esterase/lipase (GELP) family function as key enzymes in the extracellular assembly of plant biopolyesters. By combining optimized optical clearing and histological staining with tissue-specific transcriptomics and targeted metabolomics, we identified a set of GELPs that control cutin and suberin polymerization in the seed coat and leaf epidermis. These findings provide new insights into the enzymatic machinery underlying plant barrier formation and establish a mechanistic framework linking gene regulation with extracellular polymer assembly. Understanding GELP-mediated biopolymer formation opens new avenues for engineering plant surfaces to enhance resilience to environmental stress.