Biology subjects

Zeng, F.

Publications and source records attributed to Zeng, F..

5 recordsLinked to original sources

bioRxiv2018

Abnormal LTR retrotransposons formed by the recombination outside the host genome

Long terminal repeat (LTR) retrotransposons are the dominant feature of higher plant genomes, which have a similar life cycle with retrovirus. Previous studies cannot account for all observed complex LTR retrotransposon patterns. In this study, we first identified 63 complex LTR retrotransposons in rice genome, and most of complex elements harbored flanking target-site duplications (TSDs). But these complex elements in which outermost LTRs had not the most highly homologous cant be explained. We propose a new model that the homologous recombination of two new different normal LTR retrotransposon elements in the same family can occur before their integration to the rice genome. The model can explain at least fourteen complex retrotransposons formations. We also find that normal LTR retrotransposons can swap their LTRs to generate abnormal LTR retrotransposons in which LTRs are different because of homologous recombination before their integration to the genome.

genetics↗

bioRxiv2018

Molecular characterization of the viral structural gene of the first dengue virus type 1 outbreak in Xishuangbanna, a border area of China, Burma and Laos

In the context of recent arbovirus epidemics, dengue fever is becoming a greater concern around the world. In August 2017, Xishuangbanna, which is a border city of China, Burma and Laos, had its first major dengue outbreak. A total of 156 serum samples from febrile patients were collected; 97 DENV positive serum samples were screened out, and viral RNAs were successfully and directly extracted, including 77 cases from China and 20 cases from Myanmar. Phylogenetic analysis revealed that all of the strains were classified as DENV-1. There are eight epidemic dengue strains from Myanmar and 74 from Jinghong, Xishuangbanna, that were classified as cluster 1, which are the most similar to the strain of China Guangzhou 2011. There are three epidemic strains from Xishuangbanna Mengla that were classified as cluster 2, which have the closest relationship to the strain of China Hubei 2014. However, there are 12 epidemic strains from Myanmar that were classified as cluster 3, which have the closest relationship to the strain of Laos from 2008, which shows that there is a recycling epidemic trend of DENV in China. There were 236 mutations in the base, which caused 31 nonsynonymous mutations in the DENV structural protein C/prM/E genes when the strain of Xishuangbanna and Myanmar were compared with the DENV-1SS. There is no clear homologous recombination signal among these stains. Homology modeling possibly predicted a three-dimensional structure of the structural protein of these strains and revealed that they had the same three-dimensional structure and all had five predicted protein binding sites, but there are differences in binding site 434 (DENV-1SS: Thr434, DV-Jinghong: Ser434, DV-Myanmar: Ser434, DV-Mengla: Ser434). The results of the molecular clock phylogenetic and demographic reconstruction analysis show that DENV-1 became highly diversified in 1972 followed by a slightly decreased period until 2017. In conclusion, our study lays the foundation for studying the global evolution and prevalence of DENV.\n\nAuthor SummaryDengue fever (DF) is a mosquito-borne illness caused by a flavivirus. Human infections with Dengue virus (DENV) could cause fever, cutaneous rash and malaise. Xishuangbanna, which is located in the southwestern Yunnan Province and is a border city with China, Burma and Laos, was reported to have outbreak of DENV in 2013 and 2015 with different types. However, there was a large outburst of dengue in May 2017. To understand the genetic characterization, potential source and evolution of the virus, 156 serum samples were analyzed. We focused on: (i) Phylogenetic analysis of the structural protein genes sequences; (ii) Mutation, recombination analysis and predicted protein binding sites of the structural protein genes; (iii) Molecular clock and demographic reconstruction of global dengue virus serotype 1(DENV-1). Our results indicated that this is the first outbreak of DENV-1 in Xishuangbanna, dengue epidemic strains on the Burma border of China show diversification, we found a virulence site changed from I to T(amino acid position: 440), which may lead to weakened virulence of the epidemic strains. We found that the evolution of DENV-1 is dominated by regional evolution. Whats more, DENV-1 became highly diversified in 1972 followed by a slightly decreased period until 2017.

epidemiology↗

bioRxiv2018

Peripheral, intrareceptor inhibition in mosquito olfaction

How chemical signals are integrated at the peripheral sensory system of insects is still an enigma. Here we show that when coexpressed with Orco in Xenopus oocytes, an odorant receptor from the southern house mosquito, CquiOR32, generated inward (regular) currents when challenged with cyclohexanone and methyl salicylate, whereas eucalyptol and fenchone elicited inhibitory (upward) currents. Responses of CquiOR32-CquiOrco-expressing oocytes to odorants were reduced in a dose-dependent fashion by coapplication of inhibitors. This intrareceptor inhibition was also manifested in vivo in fruit flies expressing the mosquito receptor CquiOR32, as well in neurons on the antennae of the southern house mosquito. Likewise, an orthologue from the yellow fever mosquito, AaegOR71, showed intrareceptor inhibition in the Xenopus oocyte recording system and corresponding inhibition in antennal neurons. Intrareceptor inhibition was also manifested in mosquito behavior. Blood-seeking females were repelled by methyl salicylate, but repellence was significantly reduced when methyl salicylate was coapplied with eucalyptol.\n\nOne Sentence SummaryIntrareceptor inhibition was observed in mosquito odorant receptors expressed in heterologous systems, in vivo, and manifested in behavioral responses.

neuroscience↗

bioRxiv2017

DEET as a feeding deterrent

The insect repellent N,N-diethyl-3-methylbenzamide (DEET), is a multimodal compound that acts as a spatial repellent as well as an irritant (contact repellent), thus being perceived by the insects olfactory and gustatory systems as an odorant and a tastant, respectively. Soon after DEET was developed, almost 6 decades ago, it was reported that it reduced mosquito feeding on blood mixed with this repellent. It is now known that the mosquito proboscis senses contact repellents with the tips (labella) of the labium, which remain in direct contact with the outer layers of the skin, while the stylets, including the feeding deterrent sensor (labrum), penetrate the skin. We designed a behavioral assay that allowed us to tease apart contact repellency from feeding deterrence. First, we demonstrate here that when DEET was mixed with blood and covered by Parafilm(R) layers, it did not leak to the outer surface. In our assays, the mean number of landings and duration of contacts with surfaces covering blood mixed with DEET or blood plus solvent (dimethyl sulfoxide) did not differ significantly. The feeding times, however, were significantly different. When blood was mixed either with 0.1 or 1% DEET, female southern house mosquitoes spent significantly less time feeding than the time spent feeding on blood mixed only with the solvent. By contrast, there were no significant differences in the mean times of feeding on blood containing 1% picaridin and blood plus solvent. Like DEET, the contact repellent and insecticide, permethrin, caused a significant reduction in feeding time. We, therefore, concluded, that in this context, DEET and permethrin act as feeding deterrents.

animal behavior and cognition↗

bioRxiv2017

Ingredients in Victoria’s Secret Bombshell and Ivanka Trump eaux de parfums that repel mosquitoes

Insect repellents are widely used to fend off nuisance mosquitoes and, more importantly, to reduce or eliminate mosquito bites in areas where viruses and other vector-borne diseases are circulating. Synthesized more than six decades ago, DEET is the most widely used insect repellent. Plant-derived compounds are used in a plethora of commercial formulations and natural recipes to repel mosquitoes. They are also used as fragrances. We analysed Bombshell(R) to identify the constituent(s) eliciting a previously reported \"off-label\" repellence activity. The two major fragrance ingredients in Bombshell, i.e., methyl dihydrojasmonate and lilial, demonstrated strong repellence against the southern house mosquito, Culex quinquefasciatus, in laboratory assays. Both compounds activated a previously identified DEET-sensitive odorant receptor, CquiOR136. These compounds were also major constituents of Ivanka Trump eau de parfum. The methyl dihydrojasmonate content was higher in the Ivanka Trump perfume than in Bombshell, the reverse being true for lilial. Both Bombshell and Ivanka Trump eaux de parfums retained activity for as long as 6 hours in laboratory assays. Although wearing these perfumes may repel nuisance mosquitoes, their use as \"off-label\" repellents against infected mosquitoes is not recommended. A panel of 104 students (18-23 years old) conducted a blind test to compare the two eaux de parfums and showed a preference for Bombshell over Ivanka Trumps brand, particularly among women.

physiology↗