ABCG transporters export cutin precursors for the formation of the plant cuticle
Résumé
The 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.