cutine

Cutine, often written as cutin in modern texts, is a hydrophobic biopolymer that forms the main structural component of the plant cuticle, the protective outer layer covering many aerial plant organs. It functions as a barrier to water loss and pathogen entry and helps to regulate gas exchange and interaction with sunlight.

Chemically, cutine is a cross-linked polyester composed primarily of long-chain fatty acid derivatives, including omega-hydroxy fatty acids and various dicarboxylic acids. The molecules are linked by ester bonds to create a resistant, insoluble network embedded in the cuticle together with waxes and, in some tissues, suberin.

Cutine is synthesized in epidermal cells from fatty acid precursors produced by the plastids and endoplasmic reticulum. The monomers are secreted to the outer surface of the cell wall and polymerized in situ by oxidative enzymes, forming a continuous, interwoven film that blends with cuticular waxes.

The distribution and composition of cutine vary among plant species and tissues, affecting the thickness, permeability, and mechanical properties of the cuticle. In young tissues and fruits, cutine content may influence permeability to water and solutes, while in woody tissues, it may interact with suberin to contribute to protective barriers.

Research on cutine includes chemical characterization, origin, biosynthesis pathways, and its role in plant adaptation to drought and environmental stress. The term cutine is sometimes used interchangeably with cutin in older literature or in certain contexts, though modern usage favors cutin as the standard term.