A Novel Class of Defensive Compounds in Harvestmen: Hydroxy-γ-Lactones from the Phalangiid Egaenus convexus

When threatened, the harvestman Egaenus convexus (Opiliones: Phalangiidae) ejects a secretion against offenders. The secretion originates from large prosomal scent glands and is mainly composed of two isomers of 4-hydroxy-5-octyl-4,5-dihydro-3H-furan-2-one (1), a β-hydroxy-γ-lactone. The compounds were characterized by GC-MS of their microreaction derivatives, HRMS, and NMR. After the synthesis of all four possible stereoisomers of 1, followed by their separation by chiral-phase GC, the absolute configurations of the lactones in the Egaenus secretion was found to be (4S,5R)-1 (90%) and (4S,5S)-1 (10%). Hydroxy-γ-lactones represent a new class of exocrine defense compounds in harvestmen

Do Aphid Colonies Amplify their Emission of Alarm Pheromone?

When aphids are attacked by natural enemies, they emit alarm pheromone to alert conspecifics. For most aphids tested, (E)-β-farnesene (EBF) is the main, or only, constituent of the alarm pheromone. In response to alarm pheromone, alerted aphids drop off the plant, walk away, or attempt to elude predators. However, under natural conditions, EBF concentration might be low due to the low amounts emitted, to rapid air movement, or to oxidative degradation. To ensure that conspecifics are warned, aphids might conceivably amplify the alarm signal by emitting EBF in response to EBF emitted by other aphids. To examine whether such amplification occurs, we synthesized deuterated EBF (DEBF), which allowed us to differentiate between applied and aphid-derived chemical. Colonies of Acyrthosiphon pisum were treated with DEBF, and headspace volatiles were collected and analyzed for evidence of aphid-derived EBF. No aphid-derived EBF was detected, suggesting that amplification of the alarm signal does not occur. We discuss the disadvantages of alarm signal reinforcement

Proteolysis of recombinant proteins in bioengineered plant cells

Plants are increasingly used as alternative expression hosts for the production of recombinant proteins offering many advantages including higher biomass and the ability to perform posttranslational modifications on complex proteins. Key challenges for optimized accumulation of recombinant proteins in a plant system still remain, including endogenous plant proteolytic activity, which may severely compromise recombinant protein stability. Several strategies have recently been applied to improve protein stability by limiting protease action such as recombinant protein production in various sub-cellular compartments or application of protease inhibitors to limit protease action. A short update on the current strategies applied is provided here, with particular focus on sub-cellular sites previously selected for recombinant protein production and the co-expression of protease inhibitors to limit protease activity.http://www.tandfonline.com/loi/kbie20hb201

The DNMT3A R882H mutant displays altered flanking sequence preferences

The DNMT3A R882H mutation is frequently observed in acute myeloid leukemia (AML). It is located in the subunit and DNA binding interface of DNMT3A and has been reported to cause a reduction in activity and dominant negative effects. We investigated the mechanistic consequences of the R882H mutation on DNMT3A showing a roughly 40% reduction in overall DNA methylation activity. Biochemical assays demonstrated that R882H does not change DNA binding affinity, protein stability or subnuclear distribution of DNMT3A. Strikingly, DNA methylation experiments revealed pronounced changes in the flanking sequence preference of the DNMT3A-R882H mutant. Based on these results, different DNA substrates with selected flanking sequences were designed to be favored or disfavored by R882H. Kinetic analyses showed that the R882H favored substrate was methylated by R882H with 45% increased rate when compared with wildtype DNMT3A, while methylation of the disfavored substrate was reduced 7-fold. Our data expand the model of the potential carcinogenic effect of the R882H mutation by showing CpG site specific activity changes. This result suggests that R882 is involved in the indirect readout of flanking sequence preferences of DNMT3A and it may explain the particular enrichment of theR882Hmutation in cancer patients by revealing mutation specific effects

Molecular insights into antibiotic resistance - how a binding protein traps albicidin

The worldwide emergence of antibiotic resistance poses a serious threat to human health. A molecular understanding of resistance strategies employed by bacteria is obligatory to generate less-susceptible antibiotics. Albicidin is a highly potent antibacterial compound synthesized by the plant-pathogenic bacterium Xanthomonas albilineans. The drug-binding protein AlbA confers albicidin resistance to Klebsiella oxytoca. Here we show that AlbA binds albicidin with low nanomolar affinity resulting in full inhibition of its antibacterial activity. We report on the crystal structure of the drug-binding domain of AlbA (AlbAS) in complex with albicidin. Both α-helical repeat domains of AlbAS are required to cooperatively clamp albicidin, which is unusual for drug-binding proteins of the MerR family. Structure-guided NMR binding studies employing synthetic albicidin derivatives give valuable information about ligand promiscuity of AlbAS. Our findings thus expand the general understanding of antibiotic resistance mechanisms and support current drug-design efforts directed at more effective albicidin analogs

Investigation of NiOx-hole transport layers in triple cation perovskite solar cells

Perovskite solar cells with a planar p-i-n device structure offer easy processability at low temperatures, suitable for roll-to-roll fabrication on flexible substrates. Herein we investigate different hole transport layers (solution processed NiOx, sputtered NiOx, PEDOT:PSS) in planar p-i-n perovskite solar cells using the triple cation lead halide perovskite Cs0.08(MA0.17FA0.83)0.92Pb(I0.83Br0.17)3 as absorber layer. Overall, reproducible solar cell performances with power conversion efficiencies up to 12.8% were obtained using solution processed NiOx as hole transport layer in the devices. Compared to that, devices with PEDOT:PSS as hole transport layer yield efficiencies of approx. 8.4%. Further improvement of the fill factor was achieved by the use of an additional zinc oxide nanoparticle layer between the PC60BM film and the Ag electrode

Potential use of phytocystatins in crop improvement, with a particular focus on legumes

Phytocystatins are a well-characterized class of naturally-occurring protease inhibitors that function by preventing the catalysis of papain-like cysteine proteases. The action of cystatins in biotic stress resistance has been intensively studied but relatively little is known about their functions in plant growth and defence responses to abiotic stresses, such as drought. Extreme weather events such as drought and flooding will become more frequent as a result of climate change. The concepts that changes in cellular protein content and composition are required for acclimation to different abiotic stresses and that these adjustments are achieved through regulation of proteolysis are widely accepted. However, the nature and regulation of the protein turnover machinery that underpins essential stress-induced cellular re-structuring remains poorly characterised. Cysteine proteases are intrinsic to the genetic programs that underpin developmental senescence, but their functions in stress-induced senescence are poorly defined. While much remains uncertain regarding the individual cysteine protease targets of endogenous cystatins and their precise functions in the regulation of physiological processes are largely unknown, current evidence suggests that manipulation of cysteine protease activities by engineered cystatin expression might be used for to improve the resilience and quality of crop plants in the face of climate change.This work was funded by FP7-PIRSES-GA-2008-230830 (LEGIM) and PIIF-GA-2011- 299347 (Soylife; K.K.). This work was further funded by the International Foundation of Science (IFS grant C/5151-1), the NRF Thuthuka program (B.J.V.) and the NRF Incentive Funding program for rated researchers (K.K.). The funding received from the Genomic Research Institute, University of Pretoria, is hereby also acknowledged. S.G.V.W. thank the NRF/DST in South Africa for bursaries.http://jxb.oxfordjournals.org2016-06-30hb201

Agroinfiltration contributes to VP1 recombinant protein degradation

There is a growing interest in applying tobacco agroinfiltration for recombinant protein production in a plant based system. However, in such a system, the action of proteases might compromise recombinant protein production. Protease sensitivity of model recombinant foot-and-mouth disease (FMD) virus P1-polyprotein (P1) and VP1 (viral capsid protein 1) as well as E. coli glutathione reductase (GOR) were investigated. Recombinant VP1 was more severely degraded when treated with the serine protease trypsin than when treated with the cysteine protease papain. Cathepsin L- and B-like as well as legumain proteolytic activities were elevated in agroinfiltrated tobacco tissues and recombinant VP1 was degraded when incubated with such a protease-containing tobacco extract. In silico analysis revealed potential protease cleavage sites within the P1, VP1 and GOR sequences. The interaction modelling of the single VP1 protein with the proteases papain and trypsin showed greater proximity to proteolytic active sites compared to modelling with the entire P1-polyprotein fusion complex. Several plant transcripts with differential expression were detected 24 hr post-agroinfiltration when the RNA-seq technology was applied to identify changed protease transcripts using the recently available tobacco draft genome. Three candidate genes were identified coding for proteases which included the Responsive-to-Desiccation-21 (RD21) gene and genes for coding vacuolar processing enzymes 1a (NbVPE1a) and 1b (NbVPE1b). The data demonstrates that the tested recombinant proteins are sensitive to protease action and agroinfiltration induces the expression of potential proteases that can compromise recombinant protein production.The National Research Foundation (NRF) and the Genomics Research Institute (GRI), South Africa as well as NRF incentive funding to Karl Kunert and a NRF bursary to Priyen Pillay.http://www.tandfonline.com/loi/kbie202017-08-31hb2016Plant Scienc