Characterization of Arabidopsis ABCG11/WBC11, an ATP binding cassette (ABC) transporter that is required for cuticular lipid secretion^†

Abstract

SummaryABCG11/WBC11, an ATP binding cassette (ABC) transporter from Arabidopsis thaliana, is a key component of the export pathway for cuticular lipids. Arabidopsis wbc11 T-DNA insertional knock-out mutants exhibited lipidic inclusions inside epidermal cells similar to the previously characterized wax transporter mutant cer5, with a similar strong reduction in the alkanes of surface waxes. Moreover, the wbc11 knock-out mutants also showed defects not present in cer5, including post-genital organ fusions, stunted growth and a reduction in cutin load on the plant surface. A mutant line previously isolated in a forward genetics screen, called permeable leaves 1 (pel1), was identified as an allele of ABCG11/WBC11. The double knock-out wbc11 cer5 exhibited the same morphological and biochemical phenotypes as the wbc11 knock-out. A YFP-WBC11 fusion protein rescued a T-DNA knock-out mutant and was localized to the plasma membrane. These results show that WBC11 functions in secretion of surface waxes, possibly by interacting with CER5. However, unlike ABCG12/ CER5, ABCG11/WBC11 is important to the normal process of cutin formation.

Disruption of Glycosylphosphatidylinositol-Anchored Lipid Transfer Protein Gene Altered Cuticular Lipid Composition, Increased Plastoglobules, and Enhanced Susceptibility to Infection by the Fungal Pathogen Alternaria brassicicola

“…5-7). Similar results except total wax or cutin monomer loads were observed in Arabidopsis mutants, which are deficient in the plasma membrane-localized ABC transporters CER5 and ABCG11/WBC11 (Pighin et al, 2004;Bird et al, 2007). Arabidopsis cer5 mutants were found to have reduced stem cuticular wax loads and accumulated sheet-like inclusions in the cytoplasm of the epidermis, which suggests that CER5 is involved in wax export to the plant cuticle (Pighin et al, 2004).…”

“…Arabidopsis cer5 mutants were found to have reduced stem cuticular wax loads and accumulated sheet-like inclusions in the cytoplasm of the epidermis, which suggests that CER5 is involved in wax export to the plant cuticle (Pighin et al, 2004). Additionally, Arabidopsis wbc11 knockout mutants were shown to have lipidic inclusions inside epidermal cells and greatly reduced levels of wax and cutin, which indicates that ABCG11/WBC11 may function in cutin formation as well as in the secretion of surface waxes (Bird et al, 2007).…”

“…5, A and B). Therefore, further investigation is necessary to determine if LTPG1 located on the plasma membrane facilitates the export of wax precursor molecules by either association with ABC transporters such as CER5 and WBC11 (Pighin et al, 2004;Bird et al, 2007) or other unknown mechanisms. Second, it would be interesting to determine if LTPG1 is indirectly associated with vesicles containing the lipid molecules that are transported.…”

“…It has been suggested that the synthesized wax precursors are then exported from their site of synthesis in the ER to their site of deposition on the plant outer surface by a vesicular pathway (Schulz and Frommer, 2004). Recently, it was reported that ATP-binding cassette (ABC) transporters, which are located in plasma membrane of the epidermis, are required for cuticular lipid export (Pighin et al, 2004;Bird et al, 2007;Luo et al, 2007).…”

The Cytochrome P450 Enzyme CYP96A15 Is the Midchain Alkane Hydroxylase Responsible for Formation of Secondary Alcohols and Ketones in Stem Cuticular Wax of Arabidopsis

“…The current results thus define the subcellular compartment where all the major cuticular wax components are being generated, including intermediates and end products. It follows that the wax metabolites must be picked up in the ER for transport to the plasma membrane from which ATP-binding cassette transporters are thought to export them toward the cuticle (Pighin et al, 2004;Bird et al, 2007). Even though intracellular trafficking of wax molecules is crucial for successful cuticle formation, and hence for plant survival, nothing is known about the mechanisms involved.…”