title: ABC-type transporters and cuticle assembly: Linking function to polarity in epidermis cells.
abstract: 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.
authors.affiliation: Department of Plant Sciences; Weizmann Institute of Science; Rehovot Israel.
authors.forename: David
authors.initials: D
authors.lastname: Panikashvili
authors.forename: Asaph
authors.initials: A
authors.lastname: Aharoni
references.citation: Bioessays. 2008 Mar;30(3):273-7
references.pmid: 18293369
references.citation: Annu Rev Plant Biol. 2007;58:347-75
references.pmid: 17263663
references.citation: J Biol Chem. 2001 Aug 10;276(32):30231-44
references.pmid: 11346655
references.citation: Plant Cell. 2003 Mar;15(3):612-25
references.pmid: 12615936
references.citation: Science. 2004 Oct 22;306(5696):622-5
references.pmid: 15499001
references.citation: FEBS Lett. 2006 Feb 13;580(4):1183-91
references.pmid: 16364309
references.citation: Plant Cell Physiol. 2007 Dec;48(12):1790-802
references.pmid: 17989085
references.citation: Prog Lipid Res. 2003 Jan;42(1):51-80
references.pmid: 12467640
references.citation: Genetica. 2000;108(3):239-52
references.pmid: 11294610
references.citation: Science. 2004 Oct 22;306(5696):702-4
references.pmid: 15499022
references.citation: Plant Physiol. 2007 Dec;145(4):1345-60
references.pmid: 17951461
references.citation: FEBS Lett. 2006 Feb 13;580(4):1010-6
references.pmid: 16413546
references.citation: Science. 2006 May 12;312(5775):883
references.pmid: 16601151
references.citation: Nature. 2007 Jul 12;448(7150):209-12
references.pmid: 17625566
references.citation: Plant Cell Physiol. 2007 Nov;48(11):1524-33
references.pmid: 17971336
references.citation: Plant Physiol. 2005 Jan;137(1):104-16
references.pmid: 15618420
references.citation: Planta. 2005 Dec;223(1):5-19
references.pmid: 16136329
references.citation: Science. 2007 Nov 30;318(5855):1417
references.pmid: 18048682
references.citation: Nature. 2006 Mar 30;440(7084):688-91
references.pmid: 16572174
references.citation: Plant J. 2007 Nov;52(3):485-98
references.pmid: 17727615
references.citation: Curr Opin Plant Biol. 2005 Dec;8(6):613-8
references.pmid: 16182602