Transcriptional analysis of Bemisia tabaci MEAM1 cryptic species under the selection pressure of neonicotinoids imidacloprid, acetamiprid and thiamethoxam.

BACKGROUND: Neonicotinoids are widely applied in the control of the destructive agricultural pest Bemisia tabaci, and resistance against these chemicals has become a common, severe problem in the control of whiteflies. To investigate the molecular mechanism underlying resistance against nenonicotinoids in whiteflies, RNA-seq technology was applied, and the variation in the transcriptomic profiles of susceptible whiteflies and whiteflies selected by imidacloprid, acetamiprid and thiamethoxam treatment was characterized. RESULTS: A total of 90.86 GB of clean sequence data were obtained from the 4 transcriptomes. Among the 16,069 assembled genes, 584, 110 and 147 genes were upregulated in the imidacloprid-selected strain (IMI), acetamiprid-selected strain (ACE), and thiamethoxam (THI)-selected strain, respectively, relative to the susceptible strain. Detoxification-related genes including P450s, cuticle protein genes, GSTs, UGTs and molecular chaperone HSP70s were overexpressed in the selected resistant strains, especially in the IMI strain. Five genes were downregulated in all three selected resistant strains, including 2 UDP-glucuronosyltransferase 2B18-like genes (LOC 109030370 and LOC 109032577). CONCLUSIONS: Ten generations of selection with the three neonicotinoids induced different resistance levels and gene expression profiles, mainly involving cuticle protein and P450 genes, in the three selected resistant whitefly strains. The results provide a reference for research on resistance and cross-resistance against neonicotinoids in B. tabaci.

Outbreak of the South American tomato leafminer, Tuta absoluta, in the Chinese mainland: geographic and potential host range expansion.

BACKGROUND: In 2017 Tuta absoluta was identified as an invasive species in China. Due to its rapid geographic expansion and the severe crop damage it causes, T. absoluta poses a serious threat to China's tomato production industry. To determine its geographic distribution and host range, intensive surveys and routine monitoring were conducted across the Chinese mainland between 2018 and 2019. The population colonization coefficient (PCC; ratio of colonized sites and prefectures) and population occurrence index (POI; ratio of infested host species and PCCs) were calculated. RESULTS: In northwestern China, T. absoluta populations established in Xinjiang exhibited a medium PCC value (~0.03). In southwestern China, populations in Yunnan and its five neighboring provinces exhibited high (~0.50 in Yunnan and Guizhou), or low (<0.02 in Guangxi, Sichuan, Hunan, and Chongqing) PCC values. In the Chinese mainland, infestations of four crop plant species (tomato, eggplant, potato, and Chinese lantern) and two wild plant species (black nightshade and Dutch eggplant) were identified; tomatoes were infested in every colonized province. Chinese lantern and Dutch eggplant are potentially novel hosts. Yunnan, Guizhou, and Xinjiang experienced the most serious damage (POI). In southwestern China, observed damage significantly decreased with increased distance from the first discovery site of T. absoluta to the farthest county of an infested province increased. CONCLUSION: T. absoluta populations are well-established and could potentially spread to other regions of China. The present study helps to inform the establishment of better pest management guidelines and strategies in China and tomato-producing regions worldwide. © 2021 Society of Chemical Industry.

Role of several cytochrome P450s in the resistance and cross-resistance against imidacloprid and acetamiprid of Bemisia tabaci (Hemiptera: Aleyrodidae) MEAM1 cryptic species in Xinjiang, China.

Neonicotinoids are commonly used for the control of the whitefly Bemisia tabaci in cotton field. Laboratory test and field experiments have found that whitefly has a high risk of developing resistance and cross-resistance to the pesticide. Over expression of cytochrome P450 is one of the main mechanism that controls pesticide resistance in many insects. In this study we use MEAM1 whitefly, the dominant cryptic species of B. tabaci in Xinjiang cotton field, to investigate the possible resistance and cross-resistance mechanism controlled by cytochrome P450 enzymes. The P450 enzyme activity was higher in both selected strains of imidacloprid and acetamipird than that of susceptible strain. Synergism test showed that piperonyl butoxide (PBO) distinctly increased the control efficiency of imidacloprid and acetamiprid to the two resistance selected strains. Four out of 13 cytochrome genes, CYP4CS3, CYP6CX5, CYP6DW2 and CYP6CM1 were significantly up-regulated in the two selected strains based on real-time fluorescence quantitative PCR results. Other 3 genes, CYP6CX2, CYP6CX4 and CYP6DW3 were only highly expressed in the acetamiprid selected strain instead of the susceptible strain and imidacloprid selected strain. CYP6CM1 showed the highest expression level among all the 13 tested genes. No functional mutation of CYP6CM1 was found by sequence analysis. The possible role of these genes involving the resistance and cross-resistance of the whitefly MEAM1 cryptic species against neonicotinoids was discussed.

Expression and characterization of recombinant gallinacin-9 and gallinacin-8 in Escherichia coli.

Gallinacins (Gal) are antimicrobial peptides that play significant roles in innate immunity in chickens. Two Gal genes--Gal-8 and Gal-9--were cloned and sequenced from chicken liver and tongue, respectively, by reverse transcriptase-polymerase chain reaction (RT-PCR). In addition, the mRNA expression of these genes has been demonstrated across a panel of chicken tissues. It was demonstrated that Gal-9 mRNA was highly expressed in the tongue and small intestine and moderately expressed in the chicken proventriculus, lung, liver, heart, spleen, and thymus. However, Gal-8 mRNA was highly expressed in the chick small intestine and liver, and moderately expressed in the chick tongue, and lung. The recombinant fusion proteins containing Gal-9 or Gal-9 and Gal-8, namely rGal-9 and rGal-9-Gal-8, were produced and purified, respectively. Both rGal-9 and rGal-9-Gal-8 were expressed as insoluble bodies and exhibited the expected antimicrobial activity against Escherichia coli and pathogenic Streptococci suis CAB strain, as determined by the measurement of the inhibition zone and a liquid growth inhibition assay.

[An experimental study of the effects of root-canal treatment on orthodontic movement in cat cuspids].

PURPOSE: To evaluate the effectiveness of orthodontic forces in moving teeth after root canal therapy and the risk of apical resorption which may happen during orthodontic movement in an animal model. METHODS: Under general anesthesia, root canal therapy was performed on the mandibular canines on one side of 16 adult cats. Tipping movement of the canines was induced with an orthodontic spring (100 to 120 g). Eight weeks later, tooth movement was assessed from pre- and posttreatment mandibular casts, including measurement of root lengths in both radiographs and histological sections. All the data were analysed with SPSS 11.0 for windows. Student's t test was used for comparisons between paired groups. RESULTS: The results showed that teeth after root canal therapy and vital teeth moved similar distances when subjected to the same forces (P>0.05). And teeth after root canal therapy had greater loss of cementum after tooth movement than vital teeth (P<0.05), but without significant differences in radiographic root length (P>0.05). CONCLUSIONS: Teeth after root canal therapy can be moved orthodontically as readily as vital teeth when subjected to the same orthodontic forces under the conditions of the study. However, teeth after root canal therapy have more root resorption than vital teeth during orthodontic movement which may not be detected form the radiography.