The Developmental Pattern of Tomato Fruit Wax Accumulation and Its Impact on Cuticular Transpiration Barrier Properties: Effects of a Deficiency in a β-Ketoacyl-Coenzyme A Synthase (LeCER6)

Abstract

Cuticular waxes play a pivotal role in limiting transpirational water loss across the primary plant surface. The astomatous fruits of the tomato (Lycopersicon esculentum) 'MicroTom' and its lecer6 mutant, defective in a b-ketoacyl-coenzyme A synthase, which is involved in very-long-chain fatty acid elongation, were analyzed with respect to cuticular wax load and composition. The developmental course of fruit ripening was followed. Both the 'MicroTom' wild type and lecer6 mutant showed similar patterns of quantitative wax accumulation, although exhibiting considerably different water permeances. With the exception of immature green fruits, the lecer6 mutant exhibited about 3-to 8-fold increased water loss per unit time and fruit surface area when compared to the wild type. This was not the case with immature green fruits. The differences in final cuticular barrier properties of tomato fruits in both lines were fully developed already in the mature green to early breaker stage of fruit development. When the qualitative chemical composition of fruit cuticular waxes during fruit ripening was investigated, the deficiency in a b-ketoacyl-coenzyme A synthase in the lecer6 mutant became discernible in the stage of mature green fruits mainly by a distinct decrease in the proportion of n-alkanes of chain lengths . C 28 and a concomitant increase in cyclic triterpenoids. This shift in cuticular wax biosynthesis of the lecer6 mutant appears to be responsible for the simultaneously occurring increase of water permeance. Changes in cutin composition were also investigated as a function of developmental stage. This integrative functional approach demonstrates a direct relationship between cuticular transpiration barrier properties and distinct chemical modifications in cuticular wax composition during the course of tomato fruit development.

Tomato GDSL1 Is Required for Cutin Deposition in the Fruit Cuticle

“…About half of the total waxes quantified were alkanes, 24% were fatty acids, and 23% were plant triterpenoids and sterols. Waxes were mostly composed of C31 alkanes (26% of total) and d, b, or a amyrins (19.5%), in agreement with previous reports (Leide et al, 2007;Saladié et al, 2007;Isaacson et al, 2009). No significant difference in wax content and composition were detected when transgenic lines L-10, L-4, and L-3 are compared with the wild type (Table 1).…”

The Nonspecific Lipid Transfer Protein AtLtpI-4 Is Involved in Suberin Formation of Arabidopsis thaliana Crown Galls

“…Before gas chromatographic analysis, solvent-soluble and transmethylated components from crown galls and stems were transformed into the corresponding trimethylsilyl derivatives using N,O-bis-trimethylsilyl-trifluoroacetamide (Macherey-Nagel) dissolved in pyridine (Merck). The qualitative and quantitative composition was determined by referring to n-dotriacontane (C 32 ; SigmaAldrich) as an internal standard as described by Leide et al (2007).…”

The Formation and Function of Plant Cuticles

“…However, cutin deficiency that leads to organizational defects can be detrimental to the cuticle permeability (Bessire et al, 2011). In contrast to the lack of association with cutin, extensive removal of wax from tomato fruit, accomplished by brief immersion of the fruit in an organic solvent, indicates that waxes contribute approximately 95% of the cuticle-mediated resistance to water diffusion, at least in tomato fruit (Leide et al, 2007).…”

“…Specific compound classes appear to be associated with water barrier properties of the cuticle; notably, the more nonpolar components, such as alkanes, tend to be associated with decreased CWP, while nonaliphatic wax compounds, such as triterpenoids, are likely a less effective water barrier (Leide et al, 2007;Buschhaus and Jetter, 2012). This is consistent with a model in which cuticular waxes localize within either crystalline or amorphous domains of the cuticle, with aliphatic compounds forming crystallite "rafts" that are impervious to water, forcing water, and other polar metabolites, to diffuse by a circuitous route through the amorphous domains that are formed by more polar and cyclic waxes (Riederer and Schreiber, 1995).…”