Efficient heterologous biosynthesis of verazine,a metabolic precursor of the anti-cancer drug cyclopamine,in Nicotiana benthamiana

Dear Editor,Among the large number of Veratrum steroid alkaloids(Zhang et al.,2020),cyclopamine has been shown to have various inhibitory mechanisms against cancer,including inhibition of the hedgehog signaling pathway,improvement of tumor tissue microenvironment,inhibition of cell respiration,promotion of cell apoptosis,and reversal of tumor drug resistance(Liu et al.,2023).The biosynthetic pathway of verazine,a possible metabolic precursor of cyclopamine,has been discovered in Veratrum californicum(Augustin et al.,2015).However,the content of Veratrum steroid alkaloids in plants is very low(Supplemental Figure 2),so reliance on direct extraction from plants for commercial production is not feasible.A more effective strategy is to synthesize rare plant secondary metabolites using synthetic biology technology(Liu et al.,2022).

Ecosystem health assessment of urban rivers and lakes-Case study of “the six lakes”in Beijing,China

The assessment of the ecosystem health of urban rivers and lakes is the scientific basis for their management and ecological restoration.This study developed a three-level indicator system for its assessment.The results indicated that:Zhonghai and Nanhai are in the state of transition from unhealthy to critical state and all the other lakes are in unhealthy states.Water environmental quality,structure and function of the aquatic ecosystem,and the structure of waterfront areas were the constraints.Nanhai was ranked as poor and the others were all ranked as very poor.However,the ecological environment of Zhonghai and Nanhai were better than the others,the sums of the degree of membership to the healthy state and critical state were all close to 0.6.and the restorations of these lakes were moderate.The sums of the degree of membership to the healthy state and critical state of the other lakes were under 0.3,as it was difficult to restore these lakes.Some suggestions on scientific management and ecological restoration of the six lakes were proposed:①To control non-point pollution and to improve the water quality of six lakes and the water entering into these lakes;②To improve the hydrological conditions of six lakes;③To rehabilitate the aquatic ecosystem and waterfront areas.

Eco-environmental water demands for the Baiyangdian Wetland

In recent years,the hydrological characters of Baiyangdian Wetland have changed greatly,which,in turn,influence the biotic component,the structure and function of the wetland ecosystem.In order to determine the demands for water resources of ecological wetland system,a method of ecological water level coefficient was suggested to calculate the water resources demands for wetland environment use.This research showed that the minimum coefficient is 0.94 and the optimal coefficient is more than 1.10.According to these two coefficients,the ecological water level and water quantity can be estimated.The results indicate that the amount of the minimal and optimal eco-environmental water require-ments are 0.87×10^(8) and 2.78×10^(8)m^(3) in average monthly,respectively,with the maximum eco-environmental water requirement in summer and the minimum in winter.The annual change of eco-environment water demand is in accord-ing with the climate change and hydrological characters.The method of ecological water level emphasizes that wetland ecosystem adapts to the hydrological conditions,so it can be used in practice well.

Distribution and potential ecological risk of heavy metals in the typical eco-units of Haihe River Basin

The distribution and characteristics of seven heavy metals in sediments located in the typical ecological units （eco-units） （e.g., rivers, lakes, and estuaries） of Haihe River Basin were analyzed. The Hakanson potential ecological risk index was used for ecological risk assessment. The results indicated that the concentration scales of As, Hg, Cr, Cd, Pb, Cu, and Zn in the eco-units were 2.08 to 24.80 mg·g-1, 0.01 to 1135.50 mg·g-1, 28.70 to 152.73mg·g-1, 0.03 to 195765.83mg·g-1, 8.65 to 157.82mg·g-1, 6.47 to 178.61mg·g-1, and 21.09 to 1076.25 mg·g-1, respectively. The maximum concentra- tions of Hg, Cd, and Zn showed higher levels than other water bodies around the world. Hg and Cd have high concentrations in Zhangweinanhe River （1135.50 and 195765.83mg·g-1, respectively） and Haihe Estuary （790.50 and 548.47 mg·g-1, respectively）. According to the ecological factor, Cd and Hg showed very strong ecological risks. The seven heavy metals, namely, Cd, Hg, As, Cr, Pb, Cu, and Zn, exhibited ecological risk levels in descending order. Based on the potential ecological risk index, Luanhe River and Baiyangdian Lake had moderate ecological risks, whereas every site in Zhangweinanhe River and Haihe Estuary had substantial risk levels. The risk order of the typical eco-units are as follows： Zhangweinan River （2278345.68） 〉 Estuary （161914.74） 〉 Luanhe River （191.54）〉Baiyangdian Lake （120.95）. These results provided a scientific basis for water environment improve- ment and risk management of the Haihe River Basin.

Biologic risk and source diagnose of 16 PAHs from Haihe River Basin, China

Surface sediments of rivers can exhibit spatial and temporal variations in contaminant concentrations that may significantly affect risk evaluations. As to pollution control and remediation of watershed, large-scale and further background data on PAHs in China were required urgently. Spatial distribution and compositional character- istics of 16 polycyclic aromatic hydrocarbons （PAHs） in surface sediments from Haihe River Basin were investi- gated. A method based on effects range （ER） was used to assess ecosystem risk of ZPAHs （the total of 16 PAH） sensitively and accurately. The results indicated that ∑PAHs content levels ranged from 257 to 16901 μg·kg-1 dry weight. The lower tings predominated in the samples, and 2-, 3-, 4-, 5- and 6-ring PAHs accounted for 12%, 21%, 30%, 30%, and 7% respectively in total PAHs. The ratio of F1 / （F1 ＋ Py） uniformly distributed in the interval 0.20- 0.80, indicating that it may be affected by petroleum origin, oil combustion, biomass and coal combustion jointly. ∑PAHs in Cetian （S6）, Dongwushi （S19）, Handan （S20）, Aixinzhuang （S21） and Tianjin （S37） exceeded effects range low （ERL）, in which biologic effects were in a medium level with an adverse effect on biologic organisms. Thus, it is necessary to strengthen the PAHs monitoring and research of the Haihe River Basin.