Glycerol-3-Phosphate Acyltransferase Contributes to Triacylglycerol Biosynthesis,Lipid Droplet Formation,and Host Invasion in Metarhizium robertsii

Enzymes involved in the triacylglycerol (TAG) biosynthesis have been well studied in the model organisms of yeasts and animals. Among these, the isoforms of glycerol-3-phosphate acyltransferase (GPAT) redundantly catalyze the first and rate-limiting step in glycerolipid synthesis. Here, we report the functions of mrGAT, a GPAT ortholog, in an insect-pathogenic fungus, Metarhizium robertsii. Unlike in yeasts and animals, a single copy of the mrGAT gene is present in the fungal genome and the gene deletion mutant is viable. Compared to the wild type and the gene-rescued mutant, the ΔmrGAT mutant demonstrated reduced abilities to produce conidia and synthesize TAG, glycerol, and total lipids. More importantly, we found that mrGAT is localized to the endoplasmic reticulum and directly linked to the formation of lipid droplets (LDs) in fungal cells. Insect bioassay results showed that mrGAT is required for full fungal virulence by aiding fungal penetration of host cuticles. Data from this study not only advance our understanding of GPAT functions in fungi but also suggest that filamentous fungi such as M. robertsii can serve as a good model to elucidate the role of the glycerol phosphate pathway in fungal physiology, particularly to determine the mechanistic connection of GPAT to LD formation.     

Actively Tunable Fano Resonance Based on a T-Shaped Graphene Nanodimer

We present the strength modulation and frequency tuning of Fano resonance by employing a graphene nanodimer formed by two coplanar perpendicular nanostrips with different dimensions. The Fano resonance is induced by destructive interference between the bright dipole mode of a short nanostrip and the dark quadrupole mode of a long nanostrip. The strength, line width, and resonance frequency of the Fano resonance can be actively modulated by changing the spatial separation of those two graphene nanostrips and the Fermi energy of the graphene nanodimer, respectively, without re-fabricating the nanostructures. The tuning of the strength and resonance frequency can be attributed to the coupling strength and optical properties of graphene, respectively. Importantly, a figure of merit value as high as 39 is achieved in the proposed nanostructures. Our results may provide potential applications in optical switching and bio-chemical sensing.     

1H, 13C and 15N resonance assignment of truncated SUMO from Trypanosoma brucei

SUMO (small ubiquitin-like modifier) plays important roles in diverse processes by posttranslationally modifying many proteins. Here we report the resonance assignment of the truncated SUMO from Trypanosoma brucei.     

Diverse Secondary Metabolites Produced by Marine‐Derived Fungus Nigrospora sp. MA75 on Various Culture Media

Bioassay‐guided isolation of a fungal strain Nigrospora sp. MA75, an endophytic fungus obtained from the marine semi‐mangrove plant Pongamia pinnata, which was fermented on three different culture media, resulted in the isolation and identification of seven known compounds, 2, 3 , and 5 – 9 , from a medium containing 3.5% NaCl, while a new compound, 2,3‐didehydro‐19α‐hydroxy‐14‐epicochlioquinone B ( 10 ) was obtained from the medium containing 3.5% NaI. In addition, two new griseofulvin derivatives, 6‐O‐desmethyldechlorogriseofulvin ( 1 ) and 6′‐hydroxygriseofulvin ( 4 ), were isolated and identified from the rice solid medium. Dechlorogriseofulvin ( 2 ) and griseofulvin ( 3 ) were the major components in fermentation extracts of all these culture media, while compounds 1 and 4, 5 and 6 , and 10 were only present in the extract of respective culture medium. The structures of these compounds were elucidated by detailed spectroscopic analysis, and the absolute configuration of 1 was determined by CD measurement. Compounds 9 and 10 exhibited antibacterial activities toward five tested bacterial strains, while compounds 5, 6 , and 8 selectively inhibited MRSA, E. coli, and S. epidermidis, and compound 3 showed moderate activity against V. mali and S. solani. Moreover, compound 10 potently inhibited the growth of MCF‐7, SW1990, and SMMC7721 tumor cell lines with IC₅₀ values of 4, 5, and 7 μg/ml, respectively.     

Modifications of antioxidant activity and protein composition of bean leaf due to <Emphasis Type="Italic">Bean yellow mosaic virus</Emphasis> infection and salicylic acid treatments

The antioxidant status as well as protein composition of faba bean leaves infected with Bean yellow mosaic virus (BYMV) and the effect of salicylic acid application was examined in this paper. Some modifications in the antioxidant status were observed by changing some antioxidant enzymes activities and contents of antioxidant metabolites. BYMV-infected leaves revealed POD, CAT, APX and SOD induced activities while SA treatments could inhibit POD, CAT activities but induced SOD activity. The enzyme activities seemed to be SA concentration dependant. Higher H₂O₂ and MDA concentrations were recorded in virus-infected leaves than those of the corresponding controls while treatment with SA followed by virus inoculation caused lowering of MDA concentration and reducing the damage due to lipid peroxidation. Moreover, because of virus infection and/or SA treatments, an increase in the amounts of phenolics and flavonoids was noticed. As compared to the control, BYMV infection or SA application caused pronounced increase in the antioxidant activity of leaf extracts detected by DPPH assay, indicating an increase in the amounts of antioxidant compounds occurred. To test the protein composition, the contents of each protein fractions (soluble, insoluble and total) were analyzed and the change in protein patterns was visualized using SDS-PAGE. The BYMV-infected bean leaves had protein contents higher than the control indicating accumulation of pathogenesis-related proteins. Moreover, spraying SA with or without virus inoculation could accumulate soluble, insoluble and total proteins and the pattern of increase was in accordance with SA concentration. Alterations in protein patterns were observed in faba bean leaves (Vicia faba cv Giza 461) in response to BYMV infection and SA treatments. Because of BYMV infection and SA treatments, the protein profiles showed new bands in comparison to the control. Some polypeptides were highly accumulated in treatments of SA followed by virus inoculation. Changing antioxidant status and accumulation of some antioxidant metabolites as well as the pronounced alterations in the protein composition indicate a kind of plant response against pathogen invasion and in case of SA treatment it is considered a way by which a defence response was initiated and/or activated.     

The Effect of Polyhydroxylated Alkaloids on Maltase-Glucoamylase

One of the most important carbohydrate-splitting enzymes is themaltase-glucoamylase which catalyzes the hydrolysis of alpha-glucosidic linkages. Maltase-glucoamylase inhibitors during the last few years have aroused medical interests in the treatment of diabetes. They contribute to a better understanding of the mechanism of maltase-glucoamylase. At present there are many different classes of maltase-glucoamylase inhibitors. This paper focuses on alkaloidal inhibitors of maltase-glucoamylase and structure-activity relationship (SAR) studies between them in order to discover some drugs with better efficiency and lower toxicity for treating diabetes.