Biosynthesis and Transport of Plant Cuticular Waxes

Kunst, Ljerka; Jetter, Reinhard; Samuels, Lacey

doi:10.1002/9780470988718.ch5

Cited by 35 publications

(28 citation statements)

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“…Enzymes catalyzing some of the steps in the wax pathway have been characterized or their function has been proposed based on the phenotype of the corresponding mutants. These include condensing enzymes, reductases, and putative decarbonylases (Aarts et al, 1995;Xu et al, 1997;Millar et al, 1999;Todd et al, 1999;Kurata et al, 2003;Zheng et al, 2005;Kunst et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

The Transcription Factor WIN1/SHN1 Regulates Cutin Biosynthesis in Arabidopsis thaliana

et al. 2007

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The composition and permeability of the cuticle has a large influence on its ability to protect the plant against various forms of biotic and abiotic stress. WAX INDUCER1 (WIN1) and related transcription factors have recently been shown to trigger wax production, enhance drought tolerance, and modulate cuticular permeability when overexpressed in Arabidopsis thaliana. We found that WIN1 influences the composition of cutin, a polyester that forms the backbone of the cuticle. WIN1 overexpression induces compositional changes and an overall increase in cutin production in vegetative and reproductive organs, while its downregulation has the opposite effect. Changes in cutin composition are preceded by the rapid and coordinated induction of several genes known or likely to be involved in cutin biosynthesis. This transcriptional response is followed after a delay by the induction of genes associated with wax biosynthesis, suggesting that the regulation of cutin and wax production by WIN1 is a two-step process. We demonstrate that at least one of the cutin pathway genes, which encodes long-chain acyl-CoA synthetase LACS2, is likely to be directly targeted by WIN1. Overall, our results suggest that WIN1 modulates cuticle permeability in Arabidopsis by regulating genes encoding cutin pathway enzymes.

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Section: Introductionmentioning

confidence: 99%

The Transcription Factor WIN1/SHN1 Regulates Cutin Biosynthesis in Arabidopsis thaliana

et al. 2007

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“…In recent years, genetic studies have yielded some insights into wax biosynthetic pathways (Kunst et al, 2006) and uncovered a transporter that can move wax constituents across the plasma membrane (Pighin et al, 2004). However, little is known about the regulation of cuticular wax deposition, an issue of fundamental importance for the development of plant cultivars with improved cuticle properties that are more resistant to environmental stresses.…”

Section: Introductionmentioning

confidence: 99%

A Core Subunit of the RNA-Processing/Degrading Exosome Specifically Influences Cuticular Wax Biosynthesis inArabidopsis

et al. 2007

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The cuticle is an extracellular matrix composed of cutin polyester and waxes that covers aerial organs of land plants and protects them from environmental stresses. The Arabidopsis thaliana cer7 mutant exhibits reduced cuticular wax accumulation and contains considerably lower transcript levels of ECERIFERUM3/WAX2/YORE-YORE (CER3/WAX2/YRE), a key wax biosynthetic gene. We show here that CER7 protein is a putative 39-59 exoribonuclease homologous to yeast Ribonuclease PH45 (RRP45p), a core subunit of the RNA processing and degrading exosome that controls the expression of CER3/ WAX2/YRE. We propose that CER7 acts by degrading a specific mRNA species encoding a negative regulator of CER3/ WAX2/YRE transcription. A second RRP45p homolog found in Arabidopsis, designated At RRP45a, is partially functionally redundant with CER7, and complete loss of RRP45 function in Arabidopsis is lethal. To our knowledge, CER7 is currently the only example of a core exosomal subunit specifically influencing a cellular process. INTRODUCTIONThe epidermal cells of primary organs of all land plants are covered with a cuticle, a continuous lipid layer that limits nonstomatal water loss, prevents organ fusion during development (Lolle et al., 1998;Sieber et al., 2000), and protects plants against numerous biotic and abiotic environmental factors, including bacterial and fungal pathogens, temperature extremes, and UV light. The cuticle is composed of cutin, an insoluble polyester of C16 and C18 hydroxy and epoxy fatty acids and glycerol (Graç a et al., 2002;Nawrath, 2002) that is surrounded and covered with waxes, predominantly aliphatic derivatives of very long chain fatty acids easily extracted with organic solvents (Kunst and Samuels, 2003).In recent years, genetic studies have yielded some insights into wax biosynthetic pathways (Kunst et al., 2006) and uncovered a transporter that can move wax constituents across the plasma membrane (Pighin et al., 2004). However, little is known about the regulation of cuticular wax deposition, an issue of fundamental importance for the development of plant cultivars with improved cuticle properties that are more resistant to environmental stresses. Currently, the only regulatory proteins known to affect wax production are the WAX INDUCER1/SHINE family in Arabidopsis thaliana and WAX PRODUCTION ACTIVA-TOR1 in Medicago truncatula (Aharoni et al., 2004;Broun et al., 2004;Zhang et al., 2005). Overexpression of these APETALA2/ ETHYLENE RESPONSE FACTOR-type transcription factors dramatically enhances wax accumulation in leaves of transgenic plants, but their in planta roles in regulating wax deposition have not yet been confirmed by analysis of loss-of-function mutants.To identify mutants defective in regulation of wax production, we examined the expression of the cloned wax biosynthetic genes in all the wax-deficient eceriferum (cer) lines of Arabidopsis described by Koornneef et al. (1989). The cer7 mutant was found to have reduced transcript levels of CER3/WAX2/YORE-YORE (YRE) (CER3 is allelic to WAX2/...

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“…Cuticular wax components are formed by elongation of saturated fatty acyl chains and their modification either by the acyl-reduction pathway, yielding primary alcohols and esters, or by the decarbonylation pathway, leading to aldehydes, alkanes, secondary alcohols, and ketones ( Fig. 1; Kunst et al, 2006). Forward-genetic approaches have successfully identified some of the genes involved in plant wax biosynthesis from several plant species.…”

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confidence: 99%

The Cytochrome P450 Enzyme CYP96A15 Is the Midchain Alkane Hydroxylase Responsible for Formation of Secondary Alcohols and Ketones in Stem Cuticular Wax of Arabidopsis

et al. 2007

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Most aerial surfaces of plants are covered by cuticular wax that is synthesized in epidermal cells. The wax mixture on the inflorescence stems of Arabidopsis (Arabidopsis thaliana) is dominated by alkanes, secondary alcohols, and ketones, all thought to be formed sequentially in the decarbonylation pathway of wax biosynthesis. Here, we used a reverse-genetic approach to identify a cytochrome P450 enzyme (CYP96A15) involved in wax biosynthesis and characterized it as a midchain alkane hydroxylase (MAH1). Stem wax of T-DNA insertional mutant alleles was found to be devoid of secondary alcohols and ketones (mah1-1) or to contain much lower levels of these components (mah1-2 and mah1-3) than wild type. All mutant lines also had increased alkane amounts, partially or fully compensating for the loss of other compound classes. In spite of the chemical variation between mutant and wild-type waxes, there were no discernible differences in the epicuticular wax crystals on the stem surfaces. Mutant stem wax phenotypes could be partially rescued by expression of wild-type MAH1 under the control of the native promoter as well as the cauliflower mosaic virus 35S promoter. Cauliflower mosaic virus 35S-driven overexpression of MAH1 led to ectopic accumulation of secondary alcohols and ketones in Arabidopsis leaf wax, where only traces of these compounds are found in the wild type. The newly formed leaf alcohols and ketones had midchain functional groups on or next to the central carbon, thus matching those compounds in wild-type stem wax. Taken together, mutant analyses and ectopic expression of MAH1 in leaves suggest that this enzyme can catalyze the hydroxylation reaction leading from alkanes to secondary alcohols and possibly also a second hydroxylation leading to the corresponding ketones. MAH1 expression was largely restricted to the expanding regions of the inflorescence stems, specifically to the epidermal pavement cells, but not in trichomes and guard cells. MAH1-green fluorescent protein fusion proteins localized to the endoplasmic reticulum, providing evidence that both intermediate and final products of the decarbonylation pathway are generated in this subcellular compartment and must subsequently be delivered to the plasma membrane for export toward the cuticle.

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Biosynthesis and Transport of Plant Cuticular Waxes

Cited by 35 publications

References 133 publications

The Transcription Factor WIN1/SHN1 Regulates Cutin Biosynthesis in Arabidopsis thaliana

The Transcription Factor WIN1/SHN1 Regulates Cutin Biosynthesis in Arabidopsis thaliana

A Core Subunit of the RNA-Processing/Degrading Exosome Specifically Influences Cuticular Wax Biosynthesis inArabidopsis

The Cytochrome P450 Enzyme CYP96A15 Is the Midchain Alkane Hydroxylase Responsible for Formation of Secondary Alcohols and Ketones in Stem Cuticular Wax of Arabidopsis

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