Tomato GDSL1 is required for cutin deposition in the fruit cuticle.

摘要

The plant cuticle consists of cutin, a polyester of glycerol, hydroxyl and epoxy fatty acids, covered and filled by waxes. While the biosynthesis of cutin building blocks is well documented, mechanisms underlining their extracellular deposition remain unknown. Among proteins extracted from dewaxed tomato peels, GDSL1, a member of the GDSL esterase/acylhydrolase family of plant proteins, was identified. GDSL1 is strongly expressed in the epidermis of growing fruit. In GDSL1-silenced tomato lines, a significant reduction in fruit cuticle thickness and a decrease in cutin monomer content proportional to the level of GDSL1 silencing were observed. A significant decrease of wax load was observed only for cuticles of the severely silenced transgenic line. FTIR analysis of isolated cutins revealed a reduction in cutin density in silenced lines. Indeed, FTIR-attenuated total reflectance spectroscopy and atomic force microscopy imaging showed that drastic GDSL1 silencing leads to a reduction in ester bond cross-links and to the appearance of nanopores in tomato cutins. Furthermore, immunolabelling experiments attested that GDSL1 is essentially entrapped in the cuticle proper and cuticle layer. Results suggested that GDSL1 is specifically involved in the extracellular deposition of the cutin polyester in the tomato fruit cuticle.