ABC-type transporters and cuticle assembly: Linking function to polarity in epidermis cells

The aerial organs of plants are covered with a cuticle, a continuous layer overlaying the outermost cell walls of the epidermis. The cuticle is composed of two major classes of the lipid biopolymers: cutin and waxes, collectively termed cuticular lipids. Biosynthesis and transport of cuticular lipids occur predominantly in the epidermis cells. In the transport pathway, cuticular lipids are exported from their site of biosynthesis in the ER/plastid to the extracellular space through the plasma membrane and cell wall. Growing evidence suggests that ATP-binding cassette (ABC) transporters are implicated in transport of cuticular lipids across the plasma membrane of epidermal cells. The Arabidopsis ABC-type transporter protein CER5 (WBC12) was reported to act as a wax monomers transporter. In recent works, our group and others showed that a CER5-related protein, DESPERADO (DSO/WBC11), is required for cutin and wax monomers transport through the plasma membrane of Arabidopsis epidermis cells. Unlike the cer5 mutant, DSO loss-of-function had a profound effect on plant growth and development, particularly dwarfism, postgenital organ fusions, and altered epidermal cell differentiation. The partially overlapping function of CER5 and DSO and the fact that these proteins are half-size ABC transporters suggest that they might form a hetero-dimeric complex while transporting wax components. An intriguing observation was the polar localization of DSO in the distal part of epidermis cells. This polar expression might be explained by DSO localization within lipid rafts, specific plasma membrane microdomains which are associated with polar protein expression. In this review we suggest possible mechanisms for cuticular lipids transport and a link between DSO function and polar expression. Furthermore, we also discuss the subsequent transport of cuticular constituents through the hydrophobic cell wall and the possible involvement of lipid transfer proteins in this process.Key words: ABC transporter, cuticular lipids, polar expression, plasma membrane, epidermis     

A permeable cuticle in Arabidopsis leads to a strong resistance to Botrytis cinerea

The plant cuticle composed of cutin, a lipid-derived polyester, and cuticular waxes covers the aerial portions of plants and constitutes a hydrophobic extracellular matrix layer that protects plants against environmental stresses. The botrytis-resistant 1 (bre1) mutant of Arabidopsis reveals that a permeable cuticle does not facilitate the entry of fungal pathogens in general, but surprisingly causes an arrest of invasion by Botrytis. BRE1 was identified to be long-chain acyl-CoA synthetase2 (LACS2) that has previously been shown to be involved in cuticle development and was here found to be essential for cutin biosynthesis. bre1/lacs2 has a five-fold reduction in dicarboxylic acids, the typical monomers of Arabidopsis cutin. Comparison of bre1/lacs2 with the mutants lacerata and hothead revealed that an increased permeability of the cuticle facilitates perception of putative elicitors in potato dextrose broth, leading to the presence of antifungal compound(s) at the surface of Arabidopsis plants that confer resistance to Botrytis and Sclerotinia. Arabidopsis plants with a permeable cuticle have thus an altered perception of their environment and change their physiology accordingly.     

Arabidopsis Deficient in Cutin Ferulate encodes a transferase required for feruloylation of ω-hydroxy fatty acids in cutin polyester

The cuticle is a complex aliphatic polymeric layer connected to the cell wall and covers surfaces of all aerial plant organs. The cuticle prevents nonstomatal water loss, regulates gas exchange, and acts as a barrier against pathogen infection. The cuticle is synthesized by epidermal cells and predominantly consists of an aliphatic polymer matrix (cutin) and intracuticular and epicuticular waxes. Cutin monomers are primarily C(16) and C(18) unsubstituted, ω-hydroxy, and α,ω-dicarboxylic fatty acids. Phenolics such as ferulate and p-coumarate esters also contribute to a minor extent to the cutin polymer. Here, we present the characterization of a novel acyl-coenzyme A (CoA)-dependent acyl-transferase that is encoded by a gene designated Deficient in Cutin Ferulate (DCF). The DCF protein is responsible for the feruloylation of ω-hydroxy fatty acids incorporated into the cutin polymer of aerial Arabidopsis (Arabidopsis thaliana) organs. The enzyme specifically transfers hydroxycinnamic acids using ω-hydroxy fatty acids as acyl acceptors and hydroxycinnamoyl-CoAs, preferentially feruloyl-CoA and sinapoyl-CoA, as acyl donors in vitro. Arabidopsis mutant lines carrying DCF loss-of-function alleles are devoid of rosette leaf cutin ferulate and exhibit a 50% reduction in ferulic acid content in stem insoluble residues. DCF is specifically expressed in the epidermis throughout all green Arabidopsis organs. The DCF protein localizes to the cytosol, suggesting that the feruloylation of cutin monomers takes place in the cytoplasm.     

Perception of free cutin monomers by plant cells

Enzymatic degradation of plant cuticles by fungal pathogens results in the release of free cutin monomers. The hypothesis that free cutin monomers are recognized by plant cells as endogenous stress-related signals was tested in a model system consisting of cultured potato cells. Addition of cutin monomers in the micromolar range induced a transient alkalinization of the culture medium, similar to that observed with chitin or chitotetraose that served as positive control. The cutin monomers tested varied considerably in their potential to induce alkalinization, the most and least active compounds being cis -9,10-epoxy-18-hydroxystearic acid and palmitic acid, respectively. n ,16-dihydroxypalmitic acid ( n = 8, 9 or 10) was found to be the major component of potato leaf cuticle and was among the most active cutin monomers. 9,10-Dihydroxystearic acid, an analogue of the cutin monomer threo -9,10,18-trihydroxystearic acid, exhibited biological activity in a stereoselective manner, only the naturally occurring threo -stereoisomer inducing a rapid and strong alkalinization response. Alkalinization of the culture medium was inhibited by addition of the protein-kinase inhibitor K-252a, and the onset of alkalinization was paralleled by changes in phosphorylation of specific proteins. The active cutin monomers also stimulated the production of the plant stress hormone ethylene and activated defence-related genes at the mRNA level. The data provide evidence for a role of enzymatic breakdown products of plant cuticles as a new class of endogenous signal molecules.     

A functional cutin matrix is required for plant protection against water loss

The plant cuticle, a cutin matrix embedded with and covered by wax, seals the aerial organ''s surface to protect the plant against uncontrolled water loss. The cutin matrix is essential for the cuticle to function as a barrier to water loss. Recently, we identified from wild barley a drought supersensitive mutant, eibi1, which is caused by a defective cutin matrix as the result of the loss of function of HvABCG31, an ABCG full transporter. Here, we report that eibi1 epidermal cells contain lipid-like droplets, which are supposed to consist of cutin monomers that have not been transported out of the cells. The eibi1 cuticle is fragile due to a defective cutin matrix. The rice ortholog of the EIBI1 gene has a similar pattern of expression, young shoot but not flag leaf blade, as the barley gene. The model of the function of Eibi1 is discussed. The HvABCG31 full transporter functions in the export of cutin components and contributed to land plant colonization, hence also to terrestrial life evolution.Key words: ABC transporter, cuticle, cuticular wax, drought resistance, inclusion     

Formation of plant cuticle: evidence for the occurrence of the peroxygenase pathway

Cuticle plays a major role as a protective barrier in plants. Despite its physiological importance, the mode of formation of this complex structure remains poorly understood. In particular, none of the putative enzymes involved in the biosynthesis of the cutin, the matrix of cuticle, have been cloned. We have shown previously that peroxygenase is able to catalyze in vitro the epoxidation step required for the biosynthesis of C18 cutin monomers. In the present work, we have confirmed in planta that this oxidase is indeed a key enzyme involved in the formation of cutin. Thus, in maize leaves, the specific inactivation of peroxygenase by organophosphorothioates resulted in a dramatic decrease of cuticular epoxide content, as visualized by a specific histochemical technique that was accompanied by a reduced thickness of the cuticle. A strict correlation could also be established between the extent of inhibition of the peroxygenase and the modification of the cuticle triggered by a family of structurally related inhibitors. Importantly, these effects were restricted to plants that contain a cutin originating from C18 monomers. The altered cuticle of maize, treated with the peroxygenase inhibitor, was characterized by an increased permeability to pesticides. In addition, such plants became largely susceptible to infection by fungi, implying that the cuticle represents a crucial target for the modulation of the response in plant-pathogen interactions.     

The epidermis-specific extracellular BODYGUARD controls cuticle development and morphogenesis in Arabidopsis

The outermost epidermal cell wall is specialized to withstand pathogens and natural stresses, and lipid-based cuticular polymers are the major barrier against incursions. The Arabidopsis thaliana mutant bodyguard (bdg), which exhibits defects characteristic of the loss of cuticle structure not attributable to a lack of typical cutin monomers, unexpectedly accumulates significantly more cell wall-bound lipids and epicuticular waxes than wild-type plants. Pleiotropic effects of the bdg mutation on growth, viability, and cell differentiation are also observed. BDG encodes a member of the alpha/beta-hydrolase fold protein superfamily and is expressed exclusively in epidermal cells. Using Strep-tag epitope-tagged BDG for mutant complementation and immunolocalization, we show that BDG is a polarly localized protein that accumulates in the outermost cell wall in the epidermis. With regard to the appearance and structure of the cuticle, the phenotype conferred by bdg is reminiscent of that of transgenic Arabidopsis plants that express an extracellular fungal cutinase, suggesting that bdg may be incapable of completing the polymerization of carboxylic esters in the cuticular layer of the cell wall or the cuticle proper. We propose that BDG codes for an extracellular synthase responsible for the formation of cuticle. The alternative hypothesis proposes that BDG controls the proliferation/differentiation status of the epidermis via an unknown mechanism.     

Biochemical analysis of elastic and rigid cuticles of Cirsium horridulum

The cuticle is a complex structure of soluble lipids, lipid polymers and polysaccharides. In addition to its functions to reduce water loss and provide a protective barrier, its mechanical properties may be significant to plant growth and development. We investigated the cuticle of Cirsium horridulum Michx. because of its involvement in the thigmonastic contraction of staminal filaments. The staminal filaments and portions of the style are surrounded by a highly elastic cuticle in contrast to the rigid cuticle of the corolla and leaves. Our aim was to determine if the biochemical composition affected the elasticity of the cuticle. We discovered that the ratio of carbohydrates to lipids is 1:7 in floral parts but 2:1 in leaf cuticle. Esterified cutin components represented about 80% of the cuticle and di-hydroxyhexadecanoic acids were the major monomers of cutin, regardless of origin. The cutin of elastic tissues is characterized by a higher content of tri-hydroxy monomers than the cutin of rigid tissues. The data suggest that hydroxyl groups enhance the hydrophilic character of the cuticle and contribute to cuticular elasticity.     

植物角质层基因研究进展

角质层是形成于陆生植物表皮细胞壁外表面的脂质保水层。角质层的基本功能是保水,同时也在响应逆境胁迫、自我清洁及器官发育等方面发挥作用。角质层通常由角质和蜡质组成。角质是角质层的主要结构成分,其主要组分是聚酯。蜡质成分主要为极长链饱和脂肪酸及其衍生物。这些组分在内质网上合成后被转运到细胞表面,进一步形成完整的角质层结构。近年来通过对角质层相关突变体及相应基因的研究,人们对角质层在合成、转运、形成及调控等各个阶段都有了较为深入的认识。蜡质和角质的合成途径已在角质层相关基因功能的解释下逐渐浮出水面。有关角质层前体转运方面的研究,主要的突破在于ABCG全转运蛋白的发现和功能解析。在角质层形成的机理方面,角质层基因中的酯酶和脂酶类基因的研究有助于进一步认识这个复杂的过程。在基因调控方面,新的转录因子基因和角质层与环境之间的相互关系研究,也为已知的调控网络增加了新内容。该文综述了目前关于角质层相关基因的最新研究进展。     

植物角质层对非生物逆境胁迫响应研究进展

角质层,包括角质和蜡质,是主要由脂肪酸及其衍生物构成的覆盖在植物的外表面的高度疏水层,在植物生长发育过程中起到非常重要的保护屏障作用。除了在极端温度、干旱、高盐等多种非生物逆境胁迫下起到保护作用外,还能够保护植物内部组织免受细菌、真菌病原体的侵染。现就植物角质层的组成、合成途径以及与植物抗逆性,特别是与抗旱能力的关系方面的最新研究进展进行了综述。     

Development of plant cuticles: fine structure and cutin composition of Clivia miniata Reg. leaves

The fine structure and monomeric composition of the ester-cutin fraction (susceptible to BF₃/CH₃OH transesterification) of the adaxial leaf cuticle of Clivia miniata Reg. were studied in relation to leaf and cuticle development. Clivia leaves grow at their base such that cuticle and tissues increase in age from the base to the tip. The zone of maximum growth (cell expansion) was located between 1 and 4 cm from the base. During cell expansion, the projected surface area of the upper epidermal cells increased by a factor of nine. In the growth region the cuticle consists mainly of a polylamellate cuticle proper of 100–250 nm thickness. After cell expansion has ceased both the outer epidermal wall and the cuticle increase in thickness. Thickening of the cuticle is accomplished by interposition of a cuticular layer between the cuticle proper and the cell wall. The cuticular layer exhibits a reticulate fine structure and contributes most of the total mass of the cuticle at positions above 6 cm from the leaf base. The composition of ester cutin changed with the age of cuticles. In depolymerisates from young cuticles, 26 different monomers could be detected whereas in older ones their number decreased to 13. At all developmental stages, 9,16-/10,16-dihydroxyhexadecanoic acid (positional isomers not separated), 18-hydroxy-9-octadecenoic acid, 9,10,18-trihydroxyoctadecanoic acid and 9,10-epoxy-18-hydroxyoctadecanoic acid were most frequent with the epoxy alkanoic acid clearly predominating (47% at 16 cm). The results are discussed as to (i) the age dependence of cutin composition, (ii) the relationship between fine structure and composition, (iii) the composition of the cuticle proper, the cuticular layer and the non-depolymerizable cutin fraction, and (iv) the polymeric structure of cutin.Abbreviations CL cuticular layer - CP cuticle proper - MX cutin polymer matrix     

Molecular and Genetic Evidence for the Key Role of AtCaM3 in Heat-Shock Signal Transduction in Arabidopsis

The cuticle covering every plant aerial organ is largely made of cutin that consists of fatty acids, glycerol, and aromatic monomers. Despite the huge importance of the cuticle to plant development and fitness, our knowledge regarding the assembly of the cutin polymer and its integration in the complete cuticle structure is limited. Cutin composition implies the action of acyltransferase-type enzymes that mediate polymer construction through ester bond formation. Here, we show that a member of the BAHD family of acyltransferases (DEFECTIVE IN CUTICULAR RIDGES [DCR]) is required for incorporation of the most abundant monomer into the polymeric structure of the Arabidopsis (Arabidopsis thaliana) flower cutin. DCR-deficient plants display phenotypes that are typically associated with a defective cuticle, including altered epidermal cell differentiation and postgenital organ fusion. Moreover, levels of the major cutin monomer in flowers, 9(10),16-dihydroxy-hexadecanoic acid, decreased to an almost undetectable amount in the mutants. Interestingly, dcr mutants exhibit changes in the decoration of petal conical cells and mucilage extrusion in the seed coat, both phenotypes formerly not associated with cutin polymer assembly. Excessive root branching displayed by dcr mutants and the DCR expression pattern in roots pointed to the function of DCR belowground, in shaping root architecture by influencing lateral root emergence and growth. In addition, the dcr mutants were more susceptible to salinity, osmotic, and water deprivation stress conditions. Finally, the analysis of DCR protein localization suggested that cutin polymerization, possibly the oligomerization step, is partially carried out in the cytoplasmic space. Therefore, this study extends our knowledge regarding the functionality of the cuticular layer and the formation of its major constituent the polymer cutin.One of the most crucial adaptations of plants to the terrestrial environment 450 million years ago was the formation of their surface, the cuticle. The cuticular layer, which is covalently attached to the cell wall, plays multiple roles in the plant interaction with its surroundings, including the regulation of epidermal permeability and nonstomatal water loss (Sieber et al., 2000). It is also recognized to be vital for plant growth and development, for example through mediating the prevention or promotion of postgenital organ fusion and the interaction between the pollen and the pistil (Lolle et al., 1998).The major component of the cuticle is cutin, a polyester insoluble in organic solvents, consisting of aliphatics (C₁₆ and C₁₈ fatty acids), aromatics (mainly ferulic and coumaric acids), and glycerol, which are likely linked by the action of different acyltransferases. Cutin insolubility could be explained either by covalent linkage to the cell wall or by cross-linking within its aliphatic domain (Pollard et al., 2008). Recently, α,ω-dicarboxylic and in-chain hydroxy fatty acids have been reported as the characteristic monomers of cutin in Arabidopsis (Arabidopsis thaliana; Bonaventure et al., 2004; Franke et al., 2005). Cutin polymerization possibly involves the formation of an oligomeric building block for lipid polyesters composed of the three components mentioned above. Oligomerization putatively occurs within the epidermal cells, and the oligomers are further relocated with the aid of ATP-binding cassette (ABC) transporters to the extracellular matrix, where the polymerization itself might occur (Pollard et al., 2008). The recently identified GLYCEROL-3-PHOSPHATE ACYLTRANSFERASE4 (GPAT4) and GPAT8 are likely involved in oligomer formation through CoA-activated aliphatic fatty acid attachment to glycerol-3-phosphate (Li et al., 2007). However, GPATs represent only one component of the more complex machinery required for cutin oligomer and polymer formation.Recently, lipase-type enzymes have been proposed to be involved in the polymerization step that occurs in the apoplastic space of the epidermal cell extracellular matrix. The BODYGUARD (BDG) gene encodes a member of the α/β-hydrolase fold protein and is polarly localized in the outer cell walls of the Arabidopsis epidermal cells. It was suggested that BDG is involved in the completion of the apoplastic polymerization process, although the mechanism of its activity remains unclear (Kurdyukov et al., 2006a). A second gene identified in Agave americana (AgaSGNH) encodes a protein belonging to the SGNH hydrolase superfamily of lipases. Similar to BDG, AgaSGNH is polarly localized in the epidermal cell outer cell wall. It is mostly expressed in the expanding parts of young leaves where cutin biosynthesis is most active. The authors suggested that AgaSGNH is involved in cutin polymer formation through a yet unknown mechanism (Reina et al., 2007).Dicarboxylic fatty acids are the major cutin monomers in leaves and stem tissues of Arabidopsis, representing nearly half of its load. In addition to dicarboxylic acids, leaves and stems of Arabidopsis contain in-chain hydroxy fatty acids, among them 9(10),16-dihydroxy-hexadecanoic acid (up to 15% of total cutin; Nawrath, 2006). 9(10),16-Dihydroxy-hexadecanoic acid is the major cutin monomer of most angiosperms and gymnosperms (Holloway, 1982) and dominates the cutin composition of reproductive organs in many plant species, such as Vicia faba flower petals (Kolattukudy et al., 1974) and fruits of tomato (Solanum lycopersicum; Saladié et al., 2007), cherry (Prunus avium; Peschel et al., 2007), and gooseberry (Ribes uva-crispa; Kolattukudy, 2001). Early studies showed that at least half of secondary and all primary hydroxy groups of polyhydroxy fatty acids are esterified within the cutin polymer (Kolattukudy, 2001; Pollard et al., 2008). Thus, the existence of acyltransferases responsible for the acylation of either the primary or the secondary hydroxy groups of, for example, 9(10),16-dihydroxy-hexadecanoic acid, is anticipated. It is also possible that a second type of acyltransferase could utilize the CoA ester of the acid in order to incorporate it into the cutin polymeric structure.In this study, we show that the DEFECTIVE IN CUTICULAR RIDGES (DCR) gene encoding a putative acyltransferase of the Arabidopsis BAHD family is indispensable for the incorporation of 9(10),16-dihydroxy-hexadecanoic acid into the cutin polymer of reproductive and vegetative tissues. Chemical analysis shows that this acid is the most abundant Arabidopsis flower cutin monomer, representing nearly half of the cutin load. The characterization of DCR highlighted two new functions of the cuticle in decorating petal conical cells and the release of mucilage from the seed coat epidermis cells. The dramatic phenotypes of DCR mutant lines and the susceptibility of the mutant plants to water deprivation, salt, and osmotic stresses emphasize the importance of the intact cuticle in the protection against abiotic stresses. Furthermore, localization experiments of the DCR protein suggest that the process of cutin oligomerization or polymerization might take place in the cytoplasmic space. These findings shed light on cutin oligomer/polymer formation and the cuticle function in organ development.     

A member of the PLEIOTROPIC DRUG RESISTANCE family of ATP binding cassette transporters is required for the formation of a functional cuticle in Arabidopsis

Although the multilayered structure of the plant cuticle was discovered many years ago, the molecular basis of its formation and the functional relevance of the layers are not understood. Here, we present the permeable cuticle1 (pec1) mutant of Arabidopsis thaliana, which displays features associated with a highly permeable cuticle in several organs. In pec1 flowers, typical cutin monomers, such as ω-hydroxylated fatty acids and 10,16-dihydroxypalmitate, are reduced to 40% of wild-type levels and are accompanied by the appearance of lipidic inclusions within the epidermal cell. The cuticular layer of the cell wall, rather than the cuticle proper, is structurally altered in pec1 petals. Therefore, a significant role for the formation of the diffusion barrier in petals can be attributed to this layer. Thus, pec1 defines a new class of mutants. The phenotypes of the pec1 mutant are caused by the knockout of ATP BINDING CASSETTEG32 (ABCG32), an ABC transporter from the PLEIOTROPIC DRUG RESISTANCE family that is localized at the plasma membrane of epidermal cells in a polar manner toward the surface of the organs. Our results suggest that ABCG32 is involved in the formation of the cuticular layer of the cell wall, most likely by exporting particular cutin precursors from the epidermal cell.     

The identification of cutin synthase: formation of the plant polyester cutin

A hydrophobic cuticle consisting of waxes and the polyester cutin covers the aerial epidermis of all land plants, providing essential protection from desiccation and other stresses. We have determined the enzymatic basis of cutin polymerization through characterization of a tomato extracellular acyltransferase, CD1, and its substrate, 2-mono(10,16-dihydroxyhexadecanoyl)glycerol. CD1 has in vitro polyester synthesis activity and is required for cutin accumulation in vivo, indicating that it is a cutin synthase.     

Isolation and Compositional Analysis of Plant Cuticle Lipid Polyester Monomers

Terrestrial plants produce extracellular aliphatic biopolyesters that modify cell walls of specific tissues. Epidermal cells synthesize cutin, a polyester of glycerol and modified fatty acids that constitutes the framework of the cuticle that covers aerial plant surfaces. Suberin is a related lipid polyester that is deposited on the cell walls of certain tissues, including the root endodermis and the periderm of tubers, tree bark and roots. These lipid polymers are highly variable in composition among plant species, and often differ among tissues within a single species. Here, we describe a detailed protocol to study the monomer composition of cutin in Arabidopsis thaliana leaves by sodium methoxide (NaOMe)-catalyzed depolymerisation, derivatization, and subsequent gas chromatography-mass spectrometry (GC/MS) analysis. This method can be used to investigate the monomers of insoluble polyesters isolated from whole delipidated plant tissues bearing either cutin or suberin. The method can by applied not only to characterize the composition of lipid polymers in species not previously analyzed, but also as an analytical tool in forward and reverse genetic approaches to assess candidate gene function.     

Fruit cuticle lipid composition and water loss in a diverse collection of pepper (Capsicum)

Pepper (Capsicum spp.) fruits are covered by a relatively thick coating of cuticle that limits fruit water loss, a trait previously associated with maintenance of postharvest fruit quality during commercial marketing. To shed light on the chemical‐compositional diversity of cuticles in pepper, the fruit cuticles from 50 diverse pepper genotypes from a world collection were screened for both wax and cutin monomer amount and composition. These same genotypes were also screened for fruit water loss rate and this was tested for associations with cuticle composition. Our results revealed an unexpectedly large amount of variation for the fruit cuticle lipids, with a more than 14‐fold range for total wax amounts and a more than 16‐fold range for cutin monomer amounts between the most extreme accessions. Within the major wax constituents fatty acids varied from 1 to 46%, primary alcohols from 2 to 19%, n‐alkanes from 13 to 74% and triterpenoids and sterols from 10 to 77%. Within the cutin monomers, total hexadecanoic acids ranged from 54 to 87%, total octadecanoic acids ranged from 10 to 38% and coumaric acids ranged from 0.2 to 8% of the total. We also observed considerable differences in water loss among the accessions, and unique correlations between water loss and cuticle constituents. The resources described here will be valuable for future studies of the physiological function of fruit cuticle, for the identification of genes and QTLs associated with fruit cuticle synthesis in pepper fruit, and as a starting point for breeding improved fruit quality in pepper.     

Cuticle lipids on heteromorphic leaves of Populus euphratica Oliv. growing in riparian habitats differing in available soil moisture

Populus euphratica is an important native tree found in arid regions from North Africa and South Europe to China, and is known to tolerate many forms of environmental stress, including drought. We describe cuticle waxes, cutin and cuticle permeability for the heteromorphic leaves of P. euphratica growing in two riparian habitats that differ in available soil moisture. Scanning electron microscopy revealed variation in epicuticular wax crystallization associated with leaf type and site. P. euphratica leaves are dominated by cuticular wax alkanes, primary‐alcohols and fatty acids. The major cutin monomers were 10,16‐diOH C_16:0 acids. Broad‐ovate leaves (associated with adult phase growth) produced 1.3‐ and 1.6‐fold more waxes, and 2.1‐ and 0.9‐fold more cutin monomers, than lanceolate leaves (associated with juvenile phase growth) at the wetter site and drier site, respectively. The alkane‐synthesis‐associated ECERIFERUM1 (CER1), as well as ABC transporter‐ and elongase‐associated genes, were expressed at much higher levels at the drier than wetter sites, indicating their potential function in elevating leaf cuticle lipids in the dry site conditions. Higher cuticle lipid amounts were closely associated with lower cuticle permeability (both chlorophyll efflux and water loss). Our results implicate cuticle lipids as among the xeromorphic traits associated with P. euphratica adult‐phase broad‐ovate leaves. Results here provide useful information for protecting natural populations of P. euphratica and their associated ecosystems, and shed new light on the functional interaction of cuticle and leaf heterophylly in adaptation to more arid, limited‐moisture environments.