Arabidopsis ketoacyl‐CoA synthase 16 (KCS16) forms C₃₆/C₃₈ acyl precursors for leaf trichome and pavement surface wax

Abstract

The aliphatic waxes sealing plant surfaces against environmental stress are generated by fatty acid elongase complexes, each containing a β-ketoacyl-CoA synthase (KCS) enzyme that catalyses a crucial condensation forming a new C─C bond to extend the carbon backbone. The relatively high abundance of C and C alkanes derived from C and C acyl-CoAs in Arabidopsis leaf trichomes (relative to other epidermis cells) suggests differences in the elongation machineries of different epidermis cell types, possibly involving KCS16, a condensing enzyme expressed preferentially in trichomes. Here, KCS16 was found expressed primarily in Arabidopsis rosette leaves, flowers and siliques, and the corresponding protein was localized to the endoplasmic reticulum. The cuticular waxes on young leaves and isolated leaf trichomes of ksc16 loss-of-function mutants were depleted of C and C alkanes and alkenes, whereas expression of Arabidopsis KCS16 in yeast and ectopic overexpression in Arabidopsis resulted in accumulation of C and C fatty acid products. Taken together, our results show that KCS16 is the sole enzyme catalysing the elongation of C to C acyl-CoAs in Arabidopsis leaf trichomes and that it contributes to the formation of extra-long compounds in adjacent pavement cells.

Ectopic Expression of CsKCS6 From Navel Orange Promotes the Production of Very-Long-Chain Fatty Acids (VLCFAs) and Increases the Abiotic Stress Tolerance of Arabidopsis thaliana

“…Phenotypic observations and SEM analysis revealed that the density of trichomes on the leaves and stems of transgenic Arabidopsis was significantly higher than that of the WT plants ( Figures 5 , 6 , 8 ), suggesting CsKCS6 might be involved in the development of trichomes. To our surprise, although AtKCS16 is proved to catalyze the elongation of C 34 to C 38 acyl-CoAs in Arabidopsis leaf trichomes ( Hegebarth et al, 2017 ), none of the KCS6 homologous genes and other KCS family genes were reported to be related to trichome formation ( Fiebig et al, 2000 ; Hooker et al, 2002 ; Serra et al, 2009 ; Weidenbach et al, 2015 ). The divergence between our result and previous reports is probably attributed to the gene function difference among plant species.…”

Arabidopsis CER1-LIKE1 Functions in a Cuticular Very-Long-Chain Alkane-Forming Complex

“…Our results indicate that several n-alkane synthesis complexes are required to carry out the production of the very broad range of chain lengths in alkanes found in plants, from 25 up to 37 carbon atoms in leaves of Arabidopsis, for example (Bernard and Joubès, 2013;Hegebarth et al, 2017). A variety of other organisms such as bacteria, yeasts, fungi, insects, and microalgae can convert fatty acids into hydrocarbons; nevertheless, enzymes involved in alka(e)ne biosynthesis are not conserved across kingdoms, and a wide variety of pathways for hydrocarbon biosynthesis have been identified in recent years (Fu et al, 2015;Jiménez-Díaz et al, 2017).…”

Cuticular Waxes of Arabidopsis thaliana Shoots: Cell-Type-Specific Composition and Biosynthesis

“…Initially, indirect evidence came from SEM investigations of Arabidopsis stem surfaces. It had repeatedly been reported that the surface of stem pavement cells is covered with epicuticular wax crystals [ 33 , 34 , 35 , 36 , 37 ], while the surface of stem trichomes was devoid of crystals [ 6 , 7 , 38 ]. It is well established that epicuticular wax crystals form due to the accumulation of one or a few compounds in the wax mixture, and the absence or presence of crystals, hence, reflects different amounts of the crystal-forming compounds within the overall wax mixture [ 39 , 40 ].…”