cutin

Cutin is a polymeric component of the plant cuticle, the outer protective layer that covers the aerial parts of most land plants. It forms a hydrophobic, elastic network that, together with cuticular waxes, helps seal the epidermis against water loss and environmental stresses.

Chemical composition and structure: Cutin is a heterogeneous polyester composed mainly of long-chain hydroxy fatty acids, typically C16–C18, including ω-hydroxy fatty acids and α,ω-dicarboxylic acids. These monomers are interlinked by ester bonds to form a cross-linked, three-dimensional polymer. The cuticle also contains waxes and, in some tissues, suberin, resulting in a composite barrier that varies among species and tissues.

Biosynthesis and deposition: Cutin monomers are produced in epidermal cells through fatty acid elongation and modification. They are transported to the outer surface of the cell wall, where enzymatic processes catalyze their polymerization to form the cutin network. The resulting polymer is integrated with surface waxes to complete the protective barrier.

Function and significance: The primary role of cutin is to reduce nonstomatal water loss and to provide a barrier against pathogen entry and abiotic stresses. Its composition and thickness influence cuticle permeability and how plants respond to drought, heat, and UV exposure. Variation in cutin among species and environmental conditions contributes to differences in cuticle properties and plant adaptation.

Related concepts: Cutin is distinct from suberin, another plant polymer found in roots and wound-healing tissues, and from epicuticular waxes that coat the surface. In research, enzymes such as cutinases are known to degrade cutin and are used to study plant cuticles and related polymers.