Dependent activation of selected genes.FIGURE three | Polytene chromosome and Chromosome Puffs, also named Balbiani rings. For the duration of transcription DNA strands in bands can uncoil, or puff. As a result bands indicate the presence of (clusters of) genes, while interband regions are devoid of genes. Chromatin remodeling is part of the (in)activation of gene (clusters). From Google photos (Biology exams 4U: author not talked about). Copyright permission not essential.FIGURE four | Vachellia farnesiana, or the Farnese acacia tree, the plant following which “farnesol” was initially named (Wikipedia: Farnesol). From Wikimedia Commons: File: Acaciafarnesiana1web.jpg. Is inside the Public domain, no copyright permission needed. With thanks.FARNESOL AND FARNESOL-LIKE SUBSTANCES(FLS) Naming, Chemistry and Biosynthesis inside the Mevalonate PathwayFarnesol is a 15-carbon acyclic sesquiterpene alcohol that was originally extracted from the Farnese acacia tree, Vachellia farnesiana, about 1900 (Figure 4). It is actually a colorless liquid, hydrophobic, and hence immiscible in water. It is ideal recognized from its use in the perfume market. It is present in essentialoils originating from a range of plant species. It is actually employed to emphasize the odors of sweet floral perfumes as an enhancer of perfume scent (Wikipedia: 359 Farnesol). Later, just after having been identified in plant extracts, farnesol was located in all eukaryotes in which it was searched for. This is not surprising, because it is often a side product within the ubiquitous biosynthetic pathway of mevalonate-farnesylpyrophosphate pathway (Figure 5) that also yields cholesterol and steroids in vertebrates but not in arthropods and nematodes. In insects this pathway yields farnesylpyrophosphate, farnesol and juvenile hormone(s), which are esters of farnesol (Qu et al., 2018). The dichotomyFrontiers in Neuroscience | www.frontiersin.orgFebruary 2019 | Volume 13 | ArticleDe Loof and SchoofsMode of Action of FarnesolFIGURE five | The mevalonate biosynthetic pathway. It operates in all eukaryotes, as a result mammals and humans inclusive, but with some “branch-specific “variability that’s primarily linked towards the presence or absence on the gene coding for the enzyme squalene synthase that is necessary for the synthesis of squalene. This can be the precursor of cholesterol, with its a lot of functions, e.g., in the synthesis of sterols and “vertebrate-type steroid hormones”. Insects, nematodes and a few other species can’t synthesize squalene. Therefore, cholesterol can be a vitamin for them. They 1215 1216 convert farnesol into esters (Figure 2) whose juvenile hormone activity (in bioassays) is significantly 1217 greater than the mild 1 of farnesol itself. Adapted from De Loof et al., 2014, 2015a). Copyright permission not necessary.inside the mevalonate biosynthetic pathway existing SKI-178 medchemexpress between insects and vertebrates calls for some explanation. The key difference resides in their ability to synthesize cholesterol by themselves, or not. Plants and Ecdysozoa (= nematodes and arthropods) can’t synthesize cholesterol, since they lack the gene coding for squalene synthase. Vertebrates have this gene, hence they could synthesize cholesterol and use it as an intermediate in the synthesis of vertebrate steroids, e.g., of your sex steroids testosterone and estradiol. Insects also have sex steroids, Boc-Cystamine Antibody-drug Conjugate/ADC Related however they belong to the family members with the ecdysteroids (De Loof and Huybrechts, 1998; De Loof, 2015). These also occur in plants, but here their function is poorly understood. The cited dichotomy raises intriguing questio.
