Ecological Risks of Antibiotics in Urban Wetlands on the Qinghai-Tibet Plateau, China.

Although the ecological risks of antibiotics have been extensively researched globally, fewer studies have been conducted in sensitive and fragile plateau wetland ecosystems. To evaluate the ecological risk of antibiotics in plateau urban wetlands, 18 water samples, 10 plant samples, and 8 sediment samples were collected in March 2022 in the Xining urban wetlands on the Qinghai-Tibet Plateau. The liquid chromatography-electrospray ionization tandem mass spectrometry method was utilized to measure the concentrations of 15 antibiotics in three categories in three types of environmental media. Risk quotients were adopted to assess the ecological risk of antibiotics, and the principal component analysis-multiple linear regression model was used to analyze the source of antibiotics. The results showed that (1) the maximum concentrations of antibiotics in water samples, plants, and sediments reached 1220.86 ng/L, 78.30 ng/g, and 5.64 ng/g, respectively; (2) Tylosin (TYL), norfloxacin (NFX), ofloxacin (OFX), and ciprofloxacin (CFX) in water were at medium and high-risk levels, and OFX had the highest risk value, of 108.04; and (3) the results of source apportionment indicate that 58.94% of the antibiotics came from the Huangshui river and wastewater treatment plant (WWTP) near the wetlands. The current study may provide a reference for the risks and management of antibiotics in plateau urban wetlands.

The biotrophy-associated secreted protein 4 (BAS4) participates in the transition of Magnaporthe oryzae from the biotrophic to the necrotrophic phase.

The physiological and metabolic processes of host plants are manipulated and remodeled by phytopathogenic fungi during infection, revealed obvious signs of biotrophy of the hemibiotrophic pathogen. As we known that effector proteins play key roles in interaction of hemibiotrophic fungi and their host plants. BAS4 (biotrophy-associated secreted protein 4) is an EIHM (extrainvasive hyphal membrane) matrix protein that was highly expressed in infectious hyphae. In order to study whether BAS4 is involved in the transition of rice blast fungus from biotrophic to necrotrophic phase, The susceptible rice cultivar Lijiangxintuanheigu (LTH) that were pre-treated with prokaryotic expression product of BAS4 and then followed with inoculation of the blast strain, more serious blast disease symptom, more biomass such as sporulation and fungal relative growth, and lower expression level of pathogenicity-related genes appeared in lesion of the rice leaves than those of the PBS-pretreated-leaves followed with inoculation of the same blast strain, which demonstrating that BAS4 invitro changed rice defense system to facilitate infection of rice blast strain. And the susceptible rice cultivar (LTH) were inoculated withBAS4-overexpressed blast strain, we also found more serious blast disease symptom and more biomass also appeared in lesion of leaves inoculated with BAS4-overexpressed strain than those of leaves inoculated with the wild-type strain, and expression level of pathogenicity-related genes appeared lower in biotrophic phase and higher in necrotrophic phase of infection, indicating BAS4 maybe in vivo regulate defense system of rice to facilitate transition of biotrophic to necrotrophic phase. Our data demonstrates that BAS4 in vitro and in vivo participates in transition from the biotrophic to the necrotrophic phase of Magnaporthe oryzae.

Overexpression of BAS1 in rice blast fungus can promote blast fungus growth, sporulation and virulence in planta.

Background: BAS1 is biotrophy-associated secreted protein of rice blast strain (Magnaporthe oryzae). In order to study the effect of BAS1 on virulence of rice blast strain, we characterized function of BAS1 using a purified prokaryotic expression product of BAS1 and its overexpression strain. Results: Our results showed in vitro the purified expression product caused rapid callose deposition and ROS production in rice leaves and calli, indicated it triggered transient basal defense. When the purified expression product of BAS1 was sprayed onto rice leaves, and 24 h later the leaves were inoculated with blast strain, the results showed the size and number of lesions, on purified BAS1 product-pretreated leaves of the Lijiangxintuanheigu (LTH) challenged with blast strain, was higher than those in BAS1-untreated leaves directly challenged with the same strain, which suggested the defense response trigged by BAS1 can be overcome by other effectors of the fungus. More severe symptoms, higher sporulation, higher relative fungal growth and more lower expression level of defense-related genes appeared in LTH leaves challenged with overexpression strain 35S:BAS1/Mo-2 than those in LTH inoculated with wild-type strain. Conclusions: These data suggest both in vitro pretreatment with BAS1 prokaryotic expression products and overexpression in blast strains can increase virulence of blast fungus.