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.

The Hydrophobicity of Lignocellulosic Fiber Network Can Be Enhanced with Suberin Fatty Acids

“…When suberin is depolymerized, the main components are long-chain aliphatic acids, typically 80%–90% of depolymerisates [19]. Suberin fatty acids are covalently linked through esterification to ferulic acid and neighboring lignin-like polyaromatics [12,19,20,21]. Suberin is believed to form partly orderly lamellar structures [19,22].…”

Insights into the metabolic responses of two contrasting Tibetan hulless barley genotypes under low nitrogen stress

“…Distinctly, polyphenols and lipids related metabolites were significantly enriched in Z0284, which may play a basal role prior to exposure to low-N stress. It has been widely reported that biotic and abiotic factors can induce polyphenol accumulation in plants Similarly, cellular lipid levels (mainly glycerolipids) also play essential roles in response to environmental stress [38,39]. In algae, nitrogen depletion has been defined as one of the best lipid accumulator stress condition [40,41].…”

Mini Review: Transport of Hydrophobic Polymers Into the Plant Apoplast

“…Plants secrete hydrophobic compounds into the apoplast, where they contribute substantially to the plant’s structural strength and resistance against environmental stresses ( Kumar et al, 2016 ; Li-Beisson et al, 2016 ; Figure 1 ). Both lignin and suberin depositions are modifications of the secondary cell walls of land plants ( Kumar et al, 2016 ; Figure 1 ), corroborating their function in rigidifying tissues predominated by dead cells (xylem, periderm; Figure 1 ).…”

“… Overview of the localizations of lignin, suberin, cutin, and cutan; their major precursors; and hypothetical polymer structures. Major organ- and tissue-specific localizations of the four hydrophobic biopolymers are as follows: lignin in vascular bundles of shoots and roots, in structural tissues, such as leaf sclerenchyma, and in idioblasts, such as fruit stone cells ( Kumar et al, 2016 ); suberin in stem periderm and root endodermis (Casparian strip; Franke and Schreiber, 2007 ); cutin in the epidermal cuticle of leaves ( Bourgault et al, 2020 ) and flowers (“nanobridges”; Li-Beisson et al, 2016 ) and in the root cap ( Berhin et al, 2019 ); and cutan in the leaf and fruit cuticle of some species, such as Vaccinium myrtillus ( Boom et al, 2005 ; Kallio et al, 2006 ). Examples of common constituents of the four biopolymers are as follows: lignin: three monolignols (H, G, and S), ferulate monolignol ester (similar to coumarate ester, not shown), and tricin represent lignin building blocks.…”