ABCG transporters export cutin precursors for the formation of the plant cuticle

International audienceThe plant cuticle is deposited on the surface of primary plant organs, such as leaves, fruits, and floral organs,forming a diffusion barrier and protecting the plant against various abiotic and biotic stresses. Cutin, thestructural polyester of the plant cuticle, is synthesized in the apoplast. Plasma-membrane-localized ATP-binding cassette (ABC) transporters of the G family have been hypothesized to export cutin precursors.Here, we characterizeSlABCG42of tomato representing an ortholog ofAtABCG32inArabidopsis.SlABCG42expression inArabidopsiscomplements the cuticular deficiencies of theArabidopsis pec1/abcg32mutant.RNAi-dependent downregulation of both tomato genes encoding proteins highly homologous to AtABCG32(SlABCG36 and SlABCG42) leads to reduced cutin deposition and formation of a thinner cuticle in tomatofruits. By using a tobacco (Nicotiana benthamiana) protoplast system, we show that AtABCG32 andSlABCG42 have an export activity for 10,16-dihydroxy hexadecanoyl-2-glycerol, a cutin precursorin vivo.Interestingly, also freeu-hydroxy hexadecanoic acid as well as hexadecanedioic acid were exported,furthering the research on the identification of cutin precursorsin vivoand the respective mechanisms of their integration into the cutin polymer

The ABCG transporter PEC1/ABCG32 is required for the formation of the developing leaf cuticle in Arabidopsis.

The cuticle is an essential diffusion barrier on aerial surfaces of land plants whose structural component is the polyester cutin. The PERMEABLE CUTICLE1/ABCG32 (PEC1) transporter is involved in plant cuticle formation in Arabidopsis. The gpat6 pec1 and gpat4 gapt8 pec1 double and triple mutants are characterized. Their PEC1-specific contributions to aliphatic cutin composition and cuticle formation during plant development are revealed by gas chromatography/mass spectrometry and Fourier-transform infrared spectroscopy. The composition of cutin changes during rosette leaf expansion in Arabidopsis. C16:0 monomers are in higher abundance in expanding than in fully expanded leaves. The atypical cutin monomer C18:2 dicarboxylic acid is more prominent in fully expanded leaves. Findings point to differences in the regulation of several pathways of cutin precursor synthesis. PEC1 plays an essential role during expansion of the rosette leaf cuticle. The reduction of C16 monomers in the pec1 mutant during leaf expansion is unlikely to cause permeability of the leaf cuticle because the gpat6 mutant with even fewer C16:0 monomers forms a functional rosette leaf cuticle at all stages of development. PEC1/ABCG32 transport activity affects cutin composition and cuticle structure in a specific and non-redundant fashion