Cutin and Suberin Polyesters

Abstract Cutin and suberin are cell wall‐associated glycerolipid polymers that are specific to plants. Cutin forms the framework of the cuticle sealing the aerial epidermis, while suberin is present in the periderm of barks and underground organs. Suberised walls are also found in the root endodermis. Barriers based on cutin and suberin restrict the transport of water and solutes across cell walls and limit pathogen invasions. Chemical analysis shows that both polymers are polyesters composed mostly of fatty hydroxyacids, diacids and epoxyacids esterified to each other and to glycerol. Suberin, whose best‐known form is cork, usually differs from cutin (which has C16 and C18 fatty acids) by a higher content of C20–C24 aliphatics and aromatics. In the last 10 years, the identification of mutants of Arabidopsis or other model plants affected in cutin and/or suberin content has allowed the construction of a more complete picture of the polyester biosynthesis pathways, which currently include acyltransferases with unique specificities, fatty acid hydroxylases, acyl‐CoA synthetases, fatty acid elongases, fatty acyl‐CoA reductases, feruloyl transferases, ABC transporters and extracellular transacylases. Key Concepts The epidermal cells of plant aerial organs and periderm/endoderm cells synthesise the protective cell wall lipid polymers cutin and suberin respectively. Cutin and suberin are both polyesters containing glycerol and oxygenated fatty acids. Cutin structure is not completely understood and suberin structure remains controversial. Oxygenated fatty acid monomers are produced by fatty acid oxidases of the cytochrome P450 superfamily. Acylation of oxygenated fatty acids to glycerol is catalysed by special glycerol‐3‐phosphate acyltransferases. Cutin acylglycerol building blocks are exported to the cell wall and polymerised by extracellular transacylases. How suberin precursors are assembled is still unknown.