Differential resistance among host and non-host species underlies the variable success of the hemi-parasitic plant Rhinanthus minor

BACKGROUND AND AIMS: Rhinanthus minor is a root hemiparasitic plant that attacks a wide range of host species which are severely damaged by the parasite. Rhinanthus minor also attempts unsuccessfully to form connections to a range of non-hosts which in contrast are not damaged by the parasite; however, the underlying physiological basis of these differences is not fully understood. METHODS: Biomass of host-parasite combinations was studied, and histology, electron microscopy and FT-IR microspectroscopy were used to determine the cellular-level interactions between Rhinanthus haustoria (the parasite's connective structure) and the roots of a range of potential host species. RESULTS: Two distinct defence responses were observed in the non-host forbs Plantago lanceolata and Leucanthemum vulgare. Firstly, L. vulgare was able to encapsulate the parasite's invading structures preventing it from gaining access to the stele. This was supported by FT-IR microspectroscopy, used to monitor lignification in response to Rhinanthus haustoria. Secondly, host cell fragmentation was observed at the interface between the parasite and P. lanceolata. Growth data confirmed the non-host status of the two forbs whilst, in contrast, grasses and a legume which were good hosts showed no evidence of defence at the host/parasite interface. CONCLUSIONS: Variable resistance to Rhinanthus is shown for the first time to be controlled by cellular-level resistance to haustoria by either cell fragmentation or lignification at the host/parasite interface.     

Chemical characterization and toxicity evaluation of fungal pigments for potential application in food,phamarceutical and agricultural industries

Concerns associated with the use of synthetic colourants backs the demand for natural colourants. Thus, the current study aimed at characterizing crude fungal pigments produced by Penicillium multicolour, P. canescens, Talaromyces verruculosus, Fusarium solani and P. herquie. This included their antioxidant and antimicrobial properties together with acute toxicity evaluation on zebrafish embryos. The identification of pigment compounds was achieved through MS and IR data. The study demonstrated a substantial radical scavenging activity of extracts ranging from 65.49 to 74.46%, close to that of ascorbic acid (89.21%). Penicillium canescens and F. solani exhibited a strong antimicrobial activity against Escherichia coli and Enterococcus aerogenes and Salmonella typhi, Staphylococcus aureus and Bacillus cereus at MIC values ranging from 1.5 to 2.5 mg/mL. However, some levels of toxicity were observed for all extracts at a concentration range of 3–5 mg/mL. Pigment by P. multicolour, T. verruculosus and F. solani were tentatively identified through IR and MS data as sclerotiorin (yellow), rubropunctamine (red) and bostrycoidin (red). In conclusion, the study demonstrates a market potential of filamentous fungi pigments due to their antioxidant, antimicrobial activities, and prominent colours. Although there are some toxicity concerns, further tests must be done using molecular docking, albino mice and cell linings.     

Interactions between NFκB and Its Inhibitor iκB: Biophysical Characterization of a NFκB/iκB-α Complex

The N-terminal domain (1–318 amino acids) of mouse NFB (p65) has been purified to homogeneity from the soluble fraction of Escherichia coli cells expressing this protein. Its complex with a full-length iB- (MAD3, 1–317 amino acids) molecule was generated by binding the E. coli-derived iB- to the purified NFB and purifying the complex by sequential chromatography. The stoichiometry of NFB to iB in the complex was determined to be 2 to 1 by light scattering and SDS–polyacrylamide gel electrophoresis. The secondary structure of the NFB (p65) determined by Fourier-transform infrared (FTIR) spectroscopy is in good agreement with that of the p50 in the crystal structure of the p50/DNA complex, indicating that no significant structural change in NFB occurs upon binding of DNA. The FTIR spectrum of the NFB/iB complex indicates that its secondary structure is composed of 17% -helix, 39% -strand, 18% irregular structures, and 26% -turns and loops. By comparing these data to the FTIR data for NFB alone, it is concluded that the iB (MAD3) in the complex contains 35% -helix, 27% -strand, 22% irregular structures, and 16% -turns and loops. Circular dichroism (CD) analysis of a shorter form of iB (pp40) indicates that it contains at least 20% -helix and that the iB subunit accounts for nearly all of the -helix present in the NFB/iB complex, consistent with the FTIR results. The stabilities of NFB, iB, and their complex against heat-induced denaturation were investigated by following changes in CD signal. The results indicate that the thermal stability of iB is enhanced upon the formation of the NFB/iB complex.