Oils and fats of vegetable and animal origin remain an important renewable feedstock for the chemical industry. Their industrial use has increased during the last 10 years from 31 to 51 million tonnes. Remarkable achievements made in the field of oleochemistry in this timeframe are summarized herein, including the reduction of fatty esters to ethers, the selective oxidation and oxidative cleavage of double bonds, the synthesis of alkyl branched fatty compounds, the isomerizing hydroformylation and alkoxycarboxylation, and olefin metathesis. The use of oleochemicals for the synthesis of a great variety of polymeric materials has increased tremendously, too. In addition to lipases or phospholipases, other enzymes found their way into biocatalytic oleochemistry. Important achievements also generated new oil qualities in existing crop plants or by using microorganisms optimized by metabolic engineering.
Title: Changes of global gene expression and secondary metabolite accumulation during light-dependent Aspergillus nidulans development Bayram O, Feussner K, Dumkow M, Herrfurth C, Feussner I, Braus GH Ref: Fungal Genet Biol, 87:30, 2016 : PubMed
Fungal development and secondary metabolite production are coordinated by regulatory complexes as the trimeric velvet complex. Light accelerates asexual but decreases sexual development of the filamentous fungus Aspergillus nidulans. Changes in gene expression and secondary metabolite accumulation in response to environmental stimuli have been the focus of many studies, but a comprehensive comparison during entire development is lacking. We compared snapshots of transcript and metabolite profiles during fungal development in dark or light. Overall 2.014 genes corresponding to 19% of the genome were differentially expressed when submerged vegetative hyphae were compared to surface development. Differentiation was preferentially asexual in light or preferentially sexual connected to delayed asexual development in dark. Light induces significantly gene expression within the first 24-48h after the transfer to surfaces. Many light induced genes are also expressed in dark after a delay of up to two days, which might be required for preparation of enhanced sexual development. Darkness results in a massive transcriptional reprogramming causing a peak of lipid-derived fungal pheromone synthesis (psi factors) during early sexual development and the expression of genes for cell-wall degradation presumably to mobilize the energy for sexual differentiation. Accumulation of secondary metabolites like antitumoral terrequinone A or like emericellamide start under light conditions, whereas the mycotoxin sterigmatocystin or asperthecin and emodin appear under dark conditions during sexual development. Amino acid synthesis and pool rapidly drop after 72-96h in dark. Subsequent initiation of apoptotic cell-death pathways in darkness happens significantly later than in light. This illustrates that fungal adaptation in differentiation and secondary metabolite production to light conditions requires the reprogramming of one fifth of the potential of its genome.
The deposition of the (1,3)-beta-glucan cell wall polymer callose at sites of attempted penetration is a common plant defense response to intruding pathogens and part of the plant's innate immunity. Infection of the Fusarium graminearum disruption mutant Deltafgl1, which lacks the effector lipase FGL1, is restricted to inoculated wheat (Triticum aestivum) spikelets, whereas the wild-type strain colonized the whole wheat spike. Our studies here were aimed at analyzing the role of FGL1 in establishing full F. graminearum virulence. Confocal laser-scanning microscopy revealed that the Deltafgl1 mutant strongly induced the deposition of spot-like callose patches in vascular bundles of directly inoculated spikelets, while these callose deposits were not observed in infections by the wild type. Elevated concentrations of the polyunsaturated free fatty acids (FFAs) linoleic and alpha-linolenic acid, which we detected in F. graminearum wild type-infected wheat spike tissue compared with Deltafgl1-infected tissue, provided clear evidence for a suggested function of FGL1 in suppressing callose biosynthesis. These FFAs not only inhibited plant callose biosynthesis in vitro and in planta but also partially restored virulence to the Deltafgl1 mutant when applied during infection of wheat spikelets. Additional FFA analysis confirmed that the purified effector lipase FGL1 was sufficient to release linoleic and alpha-linolenic acids from wheat spike tissue. We concluded that these two FFAs have a major function in the suppression of the innate immunity-related callose biosynthesis and, hence, the progress of F. graminearum wheat infection.
Across all kingdoms of life, cells store energy in a specialized organelle, the lipid droplet. In general, it consists of a hydrophobic core of triglycerides and steryl esters surrounded by only one leaflet derived from the endoplasmic reticulum membrane to which a specific set of proteins is bound. We have chosen the unicellular organism Dictyostelium discoideum to establish kinetics of lipid droplet formation and degradation and to further identify the lipid constituents and proteins of lipid droplets. Here, we show that the lipid composition is similar to what is found in mammalian lipid droplets. In addition, phospholipids preferentially consist of mainly saturated fatty acids, whereas neutral lipids are enriched in unsaturated fatty acids. Among the novel protein components are LdpA, a protein specific to Dictyostelium, and Net4, which has strong homologies to mammalian DUF829/Tmem53/NET4 that was previously only known as a constituent of the mammalian nuclear envelope. The proteins analyzed so far appear to move from the endoplasmic reticulum to the lipid droplets, supporting the concept that lipid droplets are formed on this membrane.
The genomes of filamentous fungi comprise numerous putative gene clusters coding for the biosynthesis of chemically and structurally diverse secondary metabolites (SMs), which are rarely expressed under laboratory conditions. Previous approaches to activate these genes were based primarily on artificially targeting the cellular protein synthesis apparatus. Here, we applied an alternative approach of genetically impairing the protein degradation apparatus of the model fungus Aspergillus nidulans by deleting the conserved eukaryotic csnE/CSN5 deneddylase subunit of the COP9 signalosome. This defect in protein degradation results in the activation of a previously silenced gene cluster comprising a polyketide synthase gene producing the antibiotic 2,4-dihydroxy-3-methyl-6-(2-oxopropyl)benzaldehyde (DHMBA). The csnE/CSN5 gene is highly conserved in fungi, and therefore, the deletion is a feasible approach for the identification of new SMs.
Mycorrhizal symbioses--the union of roots and soil fungi--are universal in terrestrial ecosystems and may have been fundamental to land colonization by plants. Boreal, temperate and montane forests all depend on ectomycorrhizae. Identification of the primary factors that regulate symbiotic development and metabolic activity will therefore open the door to understanding the role of ectomycorrhizae in plant development and physiology, allowing the full ecological significance of this symbiosis to be explored. Here we report the genome sequence of the ectomycorrhizal basidiomycete Laccaria bicolor (Fig. 1) and highlight gene sets involved in rhizosphere colonization and symbiosis. This 65-megabase genome assembly contains approximately 20,000 predicted protein-encoding genes and a very large number of transposons and repeated sequences. We detected unexpected genomic features, most notably a battery of effector-type small secreted proteins (SSPs) with unknown function, several of which are only expressed in symbiotic tissues. The most highly expressed SSP accumulates in the proliferating hyphae colonizing the host root. The ectomycorrhizae-specific SSPs probably have a decisive role in the establishment of the symbiosis. The unexpected observation that the genome of L. bicolor lacks carbohydrate-active enzymes involved in degradation of plant cell walls, but maintains the ability to degrade non-plant cell wall polysaccharides, reveals the dual saprotrophic and biotrophic lifestyle of the mycorrhizal fungus that enables it to grow within both soil and living plant roots. The predicted gene inventory of the L. bicolor genome, therefore, points to previously unknown mechanisms of symbiosis operating in biotrophic mycorrhizal fungi. The availability of this genome provides an unparalleled opportunity to develop a deeper understanding of the processes by which symbionts interact with plants within their ecosystem to perform vital functions in the carbon and nitrogen cycles that are fundamental to sustainable plant productivity.
