Cloning and Characterization of the WAX2 Gene of Arabidopsis Involved in Cuticle Membrane and Wax Production

Abstract

Insertional mutagenesis of Arabidopsis ecotype C24 was used to identify a novel mutant, designated wax2 , that had alterations in both cuticle membrane and cuticular waxes. Arabidopsis mutants with altered cuticle membrane have not been reported previously. Compared with the wild type, the cuticle membrane of wax2 stems weighed 20.2% less, and when viewed using electron microscopy, it was 36.4% thicker, less opaque, and structurally disorganized. The total wax amount on wax2 leaves and stems was reduced by Ͼ 78% and showed proportional deficiencies in the aldehydes, alkanes, secondary alcohols, and ketones, with increased acids, primary alcohols, and esters. Besides altered cuticle membranes, wax2 displayed postgenital fusion between aerial organs (especially in flower buds), reduced fertility under low humidity, increased epidermal permeability, and a reduction in stomatal index on adaxial and abaxial leaf surfaces. Thus, wax2 reveals a potential role for the cuticle as a suppressor of postgenital fusion and epidermal diffusion and as a mediator of both fertility and the development of epidermal architecture (via effects on stomatal index). The cloned WAX2 gene (verified by three independent allelic insertion mutants with identical phenotypes) codes for a predicted 632-amino acid integral membrane protein with a molecular mass of 72.3 kD and a theoretical pI of 8.78. WAX2 has six transmembrane domains, a His-rich diiron binding region at the N-terminal region, and a large soluble C-terminal domain. The N-terminal portion of WAX2 is homologous with members of the sterol desaturase family, whereas the C terminus of WAX2 is most similar to members of the short-chain dehydrogenase/reductase family. WAX2 has 32% identity to CER1, a protein required for wax production but not for cuticle membrane production. Based on these analyses, we predict that WAX2 has a metabolic function associated with both cuticle membrane and wax synthesis. These studies provide new insight into the genetics and biochemistry of plant cuticle production and elucidate new associations between the cuticle and diverse aspects of plant development.

Analysis of TETRAKETIDE α-PYRONE REDUCTASE Function in Arabidopsis thaliana Reveals a Previously Unknown, but Conserved, Biochemical Pathway in Sporopollenin Monomer Biosynthesis

“…In agreement with this observation, bacteria transformed with a MS2 cDNA produce fatty alcohols from uncharacterized precursors (Doan et al, 2009). A loss-of-function mutation in the FACELESS POLLEN1/YORE-YORE/WAX2 gene that impacts exine structure and wax synthesis (Ariizumi et al, 2003;Chen et al, 2003;Kurata et al, 2003) was reported recently to be allelic to CER3, a gene previously described to fulfill an unknown function in wax synthesis (Rowland et al, 2007). DIHYDROFLA-VONOL 4-REDUCTASE-LIKE1 (DRL1), another gene required for pollen development and male fertility (Tang et al, 2009), shares sequence similarity with DIHYDROFLAVONOL REDUCTASE (DFR), a gene implicated in the biosynthesis of anthocyanins and proanthocyanidins (Shirley et al, 1992), but the DRL1 enzyme is also of unknown biochemical function.…”

Complex nested promoters control tissue-specific expression of acetyl-CoA carboxylase genes in wheat

“…VLCFA derivatives secreted on the surface of pollen and stigma have been shown to participate in pollen-stigma interaction in various plants (25)(26)(27), including wheat (28) with the lipid-rich pollen coat playing a role in plants with ''dry stigmas'' and lipid-rich secretions on ''wet stigmas'' playing the role in other plants. Our results show a high level of expression of the cytosolic ACC gene on the top surface of the ovary, suggesting an elevated rate of CW secretion by epidermal cells in this part of the organ.…”

Functional conservation and maintenance of expression pattern of FIDDLEHEAD-like genes in Arabidopsis and Antirrhinum

“…Orchestration of a number of pathways and cell-cell communication are necessary for proper differentiation of protodermal cells (Van Den Berg et al, 1997;Huelskamp and Schnittger, 1998). In Arabidopsis, studies on the FIDDLEHEAD (FDH), HIGH CARBON DIOXIDE (HIC), LACERATA (LCR) and WAX2/YORE-YORE genes have revealed a role for fatty acid metabolism in this process (Yephremov et al, 1999;Pruitt et al, 2000;Wellesen, 2001;Chen et al, 2003;Kurata et al, 2003). The FDH and HIC genes code for putative b-ketoacylCoA synthases of the FATTY ACID ELONGA-TION1 (FAE1) gene family, which consists of 21 genes in Arabidopsis (Lechelt-Kunze et al, 2003).…”