Principles of Biochemistry/Biosynthesis of lipids - …
In the cuticular wax biosynthetic pathways, the C16 and C18 fatty acids are synthesized in the plastids and exported to the cytoplasm, where they are further elongated to very-long-chain fatty acids (VLCFAs; C20 to C34) by a series of enzymes, such as 3-ketoacyl-CoA synthetases (KCS), 3-ketoacyl-CoA reductases (KCR), 3-hydroxyacyl-CoA dehydratases and trans-2-enoyl-CoA reductases (ECR). The VLCFAs are subsequently modified to their derivatives, such as alcohols, aldehydes, alkanes, ketones and wax esters, via the decarbonylation and acyl reduction pathways.,
Ethylene biosynthesis yang-cycle
These findings have implications for the interpretation ofsedimentary n-alkanes and call for a careful design of calibrationstudies using contemporary samples.
Given the high potential of n -alkanes and their δ 2 H values as a paleo-environmental proxy, research investigating the processes that determine the δ 2 H wax in living terrestrial vegetation has intensified in the past decade in order to allow a robust interpretation of sedimentary δ 2 H wax values ( Kahmen et al., 2011a, 2013a,b; Mcinerney ">
hydrocarbons: alkanes, alkenes, carotenoids - Lipid
Shang Fa Yang Pioneer in plant ethylene biochemistry. Shang Fa Yang; Ethylene; ACC; Yang Cycle 1. An early dilemma in ethylene biosynthesis was that Shang Fa Yang Chinese 楊祥發. The Yang cycle. He studied the pathway of ethylene biosynthesis and proved unequivocally the central role of methionine as a. Pioneer in plant ethylene. ACC metabolism and the Yang Cycle. Ethylene synthesis. pathway for ethylene biosynthesis, for the Yang Cycle and for his many.
fatty alcohols and aldehydes - Lipid
It has been estimated that whereas stomatal transpiration is responsible for more than 90% of aerial water loss, only a small portion of aerial water loss from the leaves and stems is mediated by cuticular transpiration. Although the portion of water loss by cuticular transpiration in aerial plant parts is relatively small, its biological significance may not be small. Our data demonstrate that the MYB96 transcription factor regulates both stomatal aperture and cuticular transpiration. Accumulation of cuticular waxes is correlated with enhanced drought resistance. It is therefore likely that although the MYB96-mediated cuticular wax biosynthesis plays a minor role in overall responses to drought, it would be critical under severe drought conditions, when many pathogens and herbivores are propagating. This view is also consistent with the notion that cuticular wax accumulation on the aerial plant parts not only prevents water loss but also provides a physical barrier against pathogen invasions and mechanical damages.
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As inferred from the gene expression profiling in the myb96-1D and myb96-1 mutants, levels of most cuticular wax components were elevated in the former but reduced in the latter. Of particular interests are alkanes, a major component of gasoline and diesel. Their levels were elevated more than 8-fold in the myb96-1D mutant, which is well consistent with their roles as strong barriers against water movement. We also found that drought stress induces accumulation of aldehydes, primary alcohols and alkanes. Accumulation of the hydrophobic components was significantly reduced in the myb96-1 mutant under drought conditions, further supporting the role of MYB96 in drought-induced cuticular wax biosynthesis. Interestingly, genes encoding cutin monomer biosynthetic enzymes were not regulated by MYB96, and contents of cutin monomers were unaltered in the myb96-1D and myb96-1 mutants. It has been known that biosynthesis of cutin monomers is not related with ABA. It is apparent that although cutin monomers also play a role in drought resistance, the MYB96 transcription factor regulates specifically cuticular wax biosynthesis in an ABA-dependent manner in inducing drought resistance.
The plant cuticle is a hydrophobic ..
Interestingly, expression of a large portion of genes involved in the cuticular wax biosynthetic pathways is altered in the myb96-1D mutant. For example, genes encoding KCS, KCR, ECR and 3-hydroxyacyl-CoA dehydratase (PAS2) are upregulated in the myb96-1D mutant. Those encoding the ECERIFERUM 3 (CER3) and CYTOCHROME P450 96 A1 (CYP96A15/MAH1) enzymes belonging to the decarbonylation pathway and encoding the CER4 and wax ester synthase/diacylglycerol acyltransferase (WSD1) enzymes functioning in the acyl reduction pathway are also induced in the mutant. Furthermore, genes encoding the lipid transfer proteins (LTPs) and ATP-binding cassette (ABC) transporters, such as WHITE-BROWN COMPLEX HOMOLOG PROTEIN 11 (WBC11) acting as a plasma membrane-localized ABC transporter that exports cutin monomers and waxes, are also upregulated in the mutant, indicating that MYB96 regulates both cuticular wax biosynthesis and transport.