Development of an agroinfiltration-based transient hairpin RNA expression system in pak choi leaves (Brassica rapa ssp. chinensis) for RNA interference against Liriomyza sativae.

The vegetable leafminer (Liriomyza sativae) is a devastating invasive pest of many vegetable crops and horticultural plants worldwide, causing serious economic loss. Conventional control strategy against this pest mainly relies on the synthetic chemical pesticides, but widespread use of insecticides easily causes insecticide resistance development and is harmful to beneficial organisms and environment. In this context, a more environmentally friendly pest management strategy based on RNA interference (RNAi) has emerged as a powerful tool to control of insect pests. Here we report a successful oral RNAi in L. sativae after feeding on pak choi (Brassica rapa ssp. chinensis) that transiently express hairpin RNAs targeting vital genes in this pest. First, potentially lethal genes are identified by searching an L. sativae transcriptome for orthologs of the widely used V-ATPase A and actin genes, then expression levels are assessed during different life stages and in different adult tissues. Interestingly, the highest expression levels for V-ATPase A are observed in the adult heads (males and females) and for actin in the abdomens of adult females. We also assessed expression patterns of the target hairpin RNAs in pak choi leaves and found that they reach peak levels 72 h post agroinfiltration. RNAi-mediated knockdown of each target was then assessed by letting adult L. sativae feed on agroinfiltrated pak choi leaves. Relative transcript levels of each target gene exhibit significant reductions over the feeding time, and adversely affect survival of adult L. sativae at 24 h post infestation in genetically unmodified pak choi plants. These results demonstrate that the agroinfiltration-mediated RNAi system has potential for advancing innovative environmentally safe pest management strategies for the control of leaf-mining species.

[Characteristics of Macrobenthos Community Structure and Their Relationships with Environmental Factors in Rivers of Beijing in Spring].

Macrobenthos from 20 sites of 17 rivers in Beijing were investigated in the spring of 2019, and the relationship between community structure characteristics and environmental factors was analyzed. A total of 64 classification units (species) of macrobenthos from 3 phyla, 6 classes, and 32 families were identified. We found that there were large spatial differences between the density composition and dominant species of macrobenthos. Mountainous river area had the highest density of aquatic insects (33.95 ind.·m-2), and the main dominant species were Simuliidae sp., Hydropsyche sp., and Paraciadius alpicola. In suburban areas, Chironomidae and Oligochaeta showed the largest average density, which was 82.58 ind.·m-2 and 36.21 ind.·m-2, respectively, and Polypedilum nubeculosum and Chironomus pallidivittatus were the dominant species in this area. Furthermore, macrobenthos in urban rivers were mainly Gastropods (88.75 ind.·m-2), and the dominant species were Bellamya aeruginosa and Bellamya purificata. Fourteen more species were found in the urban and suburban river areas than in mountain areas. According to the results of the canonical correspondence analysis, there were many factors affecting the community structure of macrobenthos, including water temperature, TN, Chl-a, pH, and human activity. Nutrient concentration was the main factor affecting the community structure of macrobenthos in the suburban river area, while human activities and water temperature were the major determinants of the macrobenthos community structure in mountainous and urban rivers.