Abstract
The hydrophobic cuticle covers the surface of the most aerial organs of land plants. The barley mutant eceriferum‐zv (cer‐zv), which is hypersensitive to drought, is unable to accumulate a sufficient quantity of cutin in its leaf cuticle. The mutated locus has been mapped to a 0.02 cM segment in the pericentromeric region of chromosome 4H. As a map‐based cloning approach to isolate the gene was therefore considered unlikely to be feasible, a comparison was instead made between the transcriptomes of the mutant and the wild type. In conjunction with extant genomic information, on the basis of predicted functionality, only two genes were considered likely to encode a product associated with cutin formation. When eight independent cer‐zv mutant alleles were resequenced with respect to the two candidate genes, it was confirmed that the gene underlying the mutation in each allele encodes a Gly‐Asp‐Ser‐Leu (GDSL)‐motif esterase/acyltransferase/lipase. The gene was transcribed in the epidermis, and its product was exclusively deposited in cell wall at the boundary of the cuticle in the leaf elongation zone, coinciding with the major site of cutin deposition. CER‐ZV is speculated to function in the deposition of cutin polymer. Its homologs were found in green algae, moss, and euphyllophytes, indicating that it is highly conserved in plant kingdom.
Highlights
The hydrophobic cuticle covers the surface of the nonwoody aerial organs of land plants
The cutin polymer deposited on the outside of the polysaccharide cell wall contributes a major structural component of the cuticle, and it is an insoluble linear, dendritic, and/or cross-linked macromolecule of hydroxy and hydroxy-epoxy 16- and 18-carbon fatty acids esterified with glycerol, and the classes of the monomers are generally conserved across land plant lineages (Fernandez et al, 2016; Fich et al, 2016)
The association between defective cutin and increased water permeability has been established repeatedly by comparing the performance of mutants and wild types, resulting in the identification of proteins involved in the phenotype: Glycerol-3phosphate acyltransferase 4 and 8 of A. thaliana participate in cutin monomer (2-monoacylglycerol) synthesis (Li et al, 2007; Yang et al, 2012)
Summary
The hydrophobic cuticle covers the surface of the nonwoody aerial organs of land plants. The cutin polymer deposited on the outside of the polysaccharide cell wall contributes a major structural component of the cuticle, and it is an insoluble linear, dendritic, and/or cross-linked macromolecule of hydroxy and hydroxy-epoxy 16- and 18-carbon fatty acids esterified with glycerol, and the classes of the monomers are generally conserved across land plant lineages (Fernandez et al, 2016; Fich et al, 2016). Tomato cutin-deficient 1 (cd1) with $ 95% reduction in wild-type fruit cutin load showed drastically increased levels of fruit desiccation (Isaacson et al, 2009) This tomato gene has recently been widely studied by different groups and been given different names, such as CD1 (Yeats et al, 2012), GDSL1 (Girard et al, 2012), and CUTIN SYNTHASE 1 (CUS1) (Philippe et al, 2016; Yeats et al, 2014). The characterization of CD1 reveals a mechanism of a Gly-Asp-Ser-Leu (GDSL)-motif esterase/acyltransferase/lipase for the construction of a cutin macromolecule, and the evidence of additional cutin synthases is expected for the presence of appreciable levels of polymeric cutin in the null mutant cd (Yeats et al, 2012)
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