Evolution of pathogenicity in obligate fungal pathogens and allied genera.

Obligate fungal pathogens (ascomycetes and basidiomycetes) and oomycetes are known to cause diseases in cereal crop plants. They feed on living cells and most of them have learned to bypass the host immune machinery. This paper discusses some of the factors that are associated with pathogenicity drawing examples from ascomycetes, basidiomycetes and oomycetes, with respect to their manifestation in crop plants. The comparisons have revealed a striking similarity in the three groups suggesting convergent pathways that have arisen from three lineages independently leading to an obligate lifestyle. This review has been written with the intent, that new information on adaptation strategies of biotrophs, modifications in pathogenicity strategies and population dynamics will improve current strategies for breeding with stable resistance.

Potential clinical utility of ERC-2 yeast phase lysate antigen for antibody detection in dogs with blastomycosis.

Four Blastomyces antigens ERC-2 (B. gilchristii, dog, Wisconsin), B5929 (human, Minnesota), 597 (human, Wisconsin), and T-27 (polar bear, Tennessee) were tested against 31 serum specimens from dogs with blastomycosis and 19 from healthy dogs. All antigens detected antibody; efficacy varied. ERC-2 showed the highest ELISA mean absorbance value of 3.00 followed by T-27. Test performance varied by sample geographic origin. Further study is needed to determine if ERC-2 antigens may be clinically useful, and whether the combination of the particular fungal species as antigen source, host animal, and the species and geographic location of the patient being tested is important for optimum test characteristics.

Development of a Tandem Repeat-Based Polymerase Chain Displacement Reaction Method for Highly Sensitive Detection of 'Candidatus Liberibacter asiaticus'.

Huanglongbing (HLB) is one of the most destructive diseases in citrus production worldwide. Early detection of HLB pathogens can facilitate timely removal of infected citrus trees in the field. However, low titer and uneven distribution of HLB pathogens in host plants make reliable detection challenging. Therefore, the development of effective detection methods with high sensitivity is imperative. This study reports the development of a novel method, tandem repeat-based polymerase chain displacement reaction (TR-PCDR), for the detection of 'Candidatus Liberibacter asiaticus', a widely distributed HLB-associated bacterium. A uniquely designed primer set (TR2-PCDR-F/TR2-PCDR-1R) and a thermostable Taq DNA polymerase mutant with strand displacement activity were used for TR-PCDR amplification. Performed in a regular thermal cycler, TR-PCDR could produce more than two amplicons after each amplification cycle. Sensitivity of the developed TR-PCDR was 10 copies of target DNA fragment. The sensitive level was proven to be 100× higher than conventional PCR and similar to real-time PCR. Data from the detection of 'Ca. L. asiaticus' with filed samples using the above three methods also showed similar results. No false-positive TR-PCDR amplification was observed from healthy citrus samples and water controls. These results thereby illustrated that the developed TR-PCDR method can be applied to the reliable, highly sensitive, and cost-effective detection of 'Ca. L. asiaticus'.

Functional Characterization of 9-/13-LOXs in Rice and Silencing Their Expressions to Improve Grain Qualities.

Lipoxygenases (LOXs) are involved in oxidative rancidity and render rice unsuitable for human consumption. Here, RNA interference- (RNAi-) induced gene expression inhibition was used to analyze the functions of the bran/seed-specific LOXs in rice. r9-LOX1 and L-2 (9-LOX category) were the candidate genes expressing a bran/seed-specific LOX, while RCI-1 was (13-LOX category) a plastid-specific LOX. Real-time PCR showed that three LOXs were cultivar/tissue specific expression on a certain level. r9-LOX1 and L-2 were generally much higher in active bran/seed than in stabilized bran, mature seed, and regenerated plant. RCI-1 was barely expressed in seed. In transgenic lines, r9-LOX1, as well as L-2, expression was dramatically downregulated, compared to the nontransgenic controls. SPME/GC-MS analysis of r9-LOX1 RNAi transgenic lines showed 74.33% decrease in nonanal content (formed during oxidation of linoleic acid by lipoxygenase), but 388.24% increase in acetic acid and 184.84% hexanal (direct products of 13-LOX). These results indicate that r9-LOX1 positively regulates the amount of nonanal but negatively regulates acetic acid and hexanal. The negative regulation may be due to a mechanism of negative feedback between LOX family members. The information will help comprehensively understand the function of the bran/seed-specific LOXs, r9-LOX1, and improve the storage quality in the future.

Microwave-assisted extraction of scutellarin from Erigeron breviscapus Hand-Mazz and its determination by high-performance liquid chromatography.

An efficient microwave-assisted extraction (MAE) technique has been developed to extract scutellarin from Erigeron breviscapus for rapid determination by high-performance liquid chromatography (HPLC). The maximum yield of scutellarin reached 1.02% in 40 min under the optimal MAE conditions with 80 degrees C of extraction temperature and 1:10 (w/v) of the solid/liquid ratio. The MAE showed obvious advantages in terms of short duration and high efficiency to extract scutellarin in comparison with heat-flux extraction. The mechanism of the enhanced extraction by microwave assistance was discussed by detecting particle size and specific surface area of plant materials and observing cell destruction of plant material by light microscopy and scanning electron microscopy. The results showed that the plant materials were significantly destroyed due to the cell rupture after MAE treatment. Afterward, the method validation for HPLC-UV analysis was developed. Calibration range was 0.1-100 microg mL(-1) for scutellarin, and correlation coefficient R was 0.9993. Limit of detection was less than 0.01 microg mL(-1). The intra- and inter-day relative standard deviation (R.S.D.) of scutellarin detection ranged from 1.58% to 2.96% and from 3.32% to 4.19%, respectively. The recovery of the method for scutellarin ranged from 96.7% to 101.9%.