Structure and Biosynthesis of Cuticular Lipids

Abstract

The structure and composition of the cutin monomers from the flower petals of Vicia faba were determined by hydrogenolysis (LiAlH4) or deuterolysis (LiAID4) followed by thin layer chromatography and combined gas-liquid chromatography and niass spectrometry. The major components were 10, 16-di. hvdroxvhexadecanoic acid (79.8%), 9,16-dihydroxyhexadecanoic acid (4.2 % ), 16-hydroxyhexadecanoic acid (4.2 %), 18-hvdroxvoctadecanoic acid (1.6%), and hexadecanoic acid (2.4%). These results show that flower petal cutin is very similar to leaf cutin of V. faba. Developing petals readily incorporated exogenous [1-_4C]palmitic acid into cutin. Direct conversion of the exogeneous acid into 16-hydroxyhexadecanoic acid, 10, 16-dihydroxy-, and 9,16-dihydroxyhexadecanoic acid was demonstrated by radio gas-liquid chromatography of their chemical degradation products. About 1 % of the exogenous J_14C]palmitic acid was incorporated into C27, C29, and C31 nalkanes, which were identified by combined gas-liquid chromatography and mass spectrometry as the major components of the hydrocarbons of V. faba flowers. The radioactivity distribution among these three alkanes (C27, 15 %; C29, 48%; C31, 38%) was similar to the per cent composition of the alkanes (C27, 12%; C29, 43%; Cai, 44%). [1-_4C]Stearic acid was also incorporated into C27, C29, and CG1 n-alkanes in good yield (3 % ). Trichloroacetate, which has been postulated to be an inhibitor of fattv acid elongation, inhibited the conversion of [1.14C]-stearic acid to alkanes, and the inhibition was greatest for the longer alkanes. Developing flower petals also incorporated exogenous C28, C30, and C31 acids into alkanes in 0.5 % to 5 % yields. [G-3H]n-octacosanoic acid (C28) was incorporated into C27. C28, and CG n-alkanes. [G-3H] elongation-decarboxylation mechanism for the biosynthesis of alkanes.Plant cuticle consists of a cross-esterified hydroxytatty acid polymer, cutin, which is embedded in a mixture of relatively nonpolar, very long chain compounds collectively called wax (12,14). In recent years much progress has been made in the determination of the structure of plant cuticular lipids. However, much of the work has been confined to leaves and fruits from which fairly intact cuticles can be isolated. The nature of the protective polymer on other parts of the plant such as flowers and roots still remains unknown. Even though recent work on the biochemistry of the cuticular lipids has enabled us to propose the most probable pathways involved in their biosynthesis, several key enzymatic steps still remain to be elucidated in cell-free preparations (12). If the flower petal synthesizes the same cuticular lipids as those found on the other parts of the plant, it might offer certain advantages as an experimental material for enzyme level studies. The results presented here constitute the first analysis of a flower cutin and show that the cutin on the V. faba flower petals is very similar, if not identical, to that found on the leaves of the same plant.One of the most common c...

Cutin Synthesis in Developing, Field-Grown Apple Fruit Examined by External Feeding of Labelled Precursors

“…The proportion of the C18 monomers increases during organ development. Thus, the cutin of a mature organ with a thicker cuticle, contains a larger portion of the C18 monomers [ 24 , 29 , 46 ]. Also, in apple fruit cutin, higher proportions of C18 monomers than C16 monomer have been reported [ 37 , 39 ].…”

Resistance of lipid films to oxygen transmission

“…The above equation defining resistance is simply a rearranged form of the general equation characterizing all molecular transport processes, i.e., the rate of transfer is equal to the driving force divided by the resistance (18). This equation is often used in the literature to express gas and vaporbarrier properties of lipid monolayers (6,(19)(20)(21)(22), cuticular membranes of plant tissue (23)(24)(25)(26)(27), and wax coatings applied to fresh fruit 128).…”

The effects of inhibitors on the biosynthesis of the long chain lipids with even carbon numbers in barley spike epicuticular wax

“…TCA was the first of the chemicals investigated and subsequently shown to inhibit elongation in a number of plant systems; B. oleracea (19,21,36), Nicotiana tabacum (22), P. sativum (5) and Vicia faba (30). A single elongation block has not been identified, instead the severity of the inhibition increased as the chain length increased.…”