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Beta-amyloid (Aβ) peptides are the major constituents of senile plaques in the brains of Alzheimer’s disease (AD) patients. Aβ monomers (AβMs) can coalesce to form small, soluble oligomers (AβOs), followed by reorganization and assembly into long, thread-like fibrils (AβFs). Recently, soluble AβOs have been regarded as reliable molecular biomarkers for the diagnosis of AD because of their high toxicity for neuronal synapse and high concentration levels in the brains of AD patients. In this work, we reported a label-free, sensitive and selective method for visual and fluorescent detection of AβOs based on the inner filter effect (IFE) of gold nanoparticles (AuNPs) on the fluorescence of CdTe quantum dots (QDs). Specifically, the fluorescence of CdTe QDs was quenched significantly by AuNPs through the IFE. PrP(95–110), an AβOs-specific binding peptide from cellular prion protein, triggered the aggregation and color change of AuNPs suspension; thus, the IFE of AuNPs on the fluorescence of CdTe QDs was weakened and the fluorescence intensity was recovered. However, in the presence of AβOs, the specific interaction of AβOs and PrP(95–110) prevented the absorption of PrP(95–110) onto the surface of AuNPs. As a result, the aggregation of AuNPs was inhibited and the fluorescence intensity of CdTe QDs was quenched again. This label-free method is specific for detection of AβOs but not for AβMs and AβFs. The detection limits were found to be 0.5 nM for the visual assay and 0.2 nM for the fluorescent detection. We believe that this work would be valuable for many investigations related to AD diagnosis and drug discovery. [ABSTRACT FROM AUTHOR]

Tall fescue ( Festuca arundinacea Schreb.) is an important grass widely used in North Carolina and other transition zone states in the US for turf and as forage. Brown patch caused by subgroup AG1-AI of Rhizoctonia solani is the most severe and frequently occurring fungal disease for tall fescue plants. The objective of this research was to genetically engineer tall fescue to improve its resistance to the pathogen. The gene ( Pen4- 1) of a novel antimicrobial peptide-Penaeidin 4-1 from a shrimp species was introduced into tall fescue var. 'Coronado' through Agrobacterium-mediated transformation. Among the five transgenic plants containing the Pen4- 1 transgene, four of them displayed significantly higher level of resistance against R. solani subgroup AG1-IA, with two being highly resistant ( p < 0.001). Up to 75 % reduction of the lesion size was achieved. The results indicate that Pen4- 1 confers resistance to various subgroups of R. solani and is a promising candidate for engineered resistance to a wide-spectrum pathogens in tall fescue. [ABSTRACT FROM AUTHOR]

Key message: Transgenic tall fescue plants expressing RNAi constructs of essential genes of Rhizoctonia solani were resistant to R. solani. Abstract: Tall fescue ( Festuca arundinacea Schreb.) is an important turf and forage grass species widely used for home lawns and on golf courses in North Carolina and other transition zone states in the US. The most serious and frequently occurring disease of tall fescue is brown patch, caused by a basidiomycete fungus, Rhizoctonia solani. This research demonstrates resistance to brown patch disease achieved by the application of host induced gene silencing. We transformed tall fescue with RNAi constructs of four experimentally determined 'essential' genes from R. solani (including genes encoding RNA polymerase, importin beta-1 subunit, Cohesin complex subunit Psm1, and a ubiquitin E3 ligase) to suppress expression of those genes inside the fungus and thus inhibit fungal infection. Four gene constructs were tested, and 19 transgenic plants were obtained, among which 12 plants had detectable accumulation of siRNAs of the target genes. In inoculation tests, six plants displayed significantly improved resistance against R. solani. Lesion size was reduced by as much as 90 %. Plants without RNAi accumulation did not show resistance. To our knowledge, this is the first case that RNAi constructs of pathogen genes introduced into a host plant can confer resistance against a necrotrophic fungus. [ABSTRACT FROM AUTHOR]