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Tomato fruit cuticular waxes and their effects on transpiration barrier properties: functional characterization of a mutant deficient in a very-long-chain fatty acid beta-ketoacyl-CoA synthase

TitleTomato fruit cuticular waxes and their effects on transpiration barrier properties: functional characterization of a mutant deficient in a very-long-chain fatty acid beta-ketoacyl-CoA synthase
Publication TypeJournal Article
Year of Publication2004
AuthorsVogg, G, Fischer, S, Leide, J, Emmanuel, E, Jetter, R, Levy, AA, Riederer, M
JournalJournal of Experimental Botany
Volume55
Pagination1401-1410
Date PublishedJun
Type of ArticleArticle
ISBN Number0022-0957
KeywordsARABIDOPSIS-THALIANA, BARRIER, BICOLOR L MOENCH, CITRUS LEAF CUTICLES, CONDENSING ENZYME, CONDUCTANCE, cuticle, ECERIFERUM CER MUTANTS, EPICUTICULAR WAX, EPICUTICULAR WAXES, EPIDERMAL, intracuticular wax, PRUNUS-LAUROCERASUS L, tomato, transpiration, TRANSPORT-PROPERTIES, WATER PERMEABILITY
Abstract

Cuticular waxes play a pivotal role in limiting transpirational water loss across the plant surface. The correlation between the chemical composition of the cuticular waxes and their function as a transpiration barrier is still unclear. In the present study, intact tomato fruits (Lycopersicon esculentum) are used, due to their astomatous surface, as a novel integrative approach to investigate this composition-function relationship: wax amounts and compositions of tomato were manipulated before measuring unbiased cuticular transpiration. First, successive mechanical and extractive wax-removal steps allowed the selective modification of epi- and intracuticular wax layers. The epicuticular film consisted exclusively of very-long-chain aliphatics, while the intracuticular compartment contained large quantities of pentacyclic triterpenoids as well. Second, applying reverse genetic techniques, a loss-of-function mutation with a transposon insertion in a very-long-chain fatty acid elongase beta-ketoacyl-CoA synthase was isolated and characterized. Mutant leaf and fruit waxes were deficient in n-alkanes and aldehydes with chain lengths beyond C-30, while shorter chains and branched hydrocarbons were not affected. The mutant fruit wax also showed a significant increase in intracuticular triterpenoids. Removal of the epicuticular wax layer, accounting for one-third of the total wax coverage on wild-type fruits, had only moderate effects on transpiration. By contrast, reduction of the intracuticular aliphatics in the mutant to approximately 50% caused a 4-fold increase in permeability. Hence, the main portion of the transpiration barrier is located in the intracuticular wax layer, largely determined by the aliphatic constituents, but modified by the presence of triterpenoids, whereas epicuticular aliphatics play a minor role.

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