Transgenic cry1Ab/vip3H+epsps Rice with Insect and Herbicide Resistance Acted No Adverse Impacts on the Population Growth of a Non-Target Herbivore, the White-Backed Planthopper, Under Laboratory and Field Conditions

Numerous Bt rice lines expressing Cry protein derived from Bacillus thuringiensis Berliner （Bt） have been developed since 1989. However, the potential risks posed by Bt rice on non-target organisms still remain debate. The white-backed planthopper （WBPH）, Sogatella furcifera （Horváth）, is one of the most economically important insect pests of rice in Asian countries and also one of the main non-target herbivores of transgenic rice. In the current study, impacts of transgenic cry1Ab/vip3H＋epsps rice （G6H1） with both insect and herbicide resistance on WBPH were evaluated to ascertain whether this transgenic rice line had potential risks for this sap-sucking pest under laboratory and ifeld conditions. The laboratory results showed that no signiifcant difference in egg developmental duration, nymphal survival rate and female fecundity was found for WBPH between G6H1 and its non-transgenic isoline （XS110）. However, the development duration of nymphs was signiifcantly shorter and female longevity signiifcantly longer when WBPH fed on G6H1 by comparison with those on its control. To verify the results found in laboratory, a 3-yr ifeld trial was conducted to monitor WBPH population using both the vacuum-suction machine and beat plate methods. Although the seasonal density of WBPH nymphs and total density of nymphs and adults were not signiifcantly affected by transgenic rice regardless of the sampling methods, the seasonal density of WBPH adults in transgenic rice plots was slightly lower than that in the control when using the vacuum-suction machine. Based on these results both from laboratory and ifeld, it is clear that our tested transgenic rice line will not lead higher population of WBPH. However, long-term ifeld experiments to monitor the population dynamics of WPBH at large scale need to be conducted to conifrm the present conclusions in future.

Effects of Transgenic Bt+CpTI Cotton on Field Abundance of Non-Target Pests and Predators in Xinjiang, China

Transgenic insect-resistant cotton is being increasingly planted in Xinjiang cotton-planting regions, where geographical climate conditions and species composition of pests and natural enemies are greatly unique in China. Limited studies have been conducted on the ecological impacts of transgenic insect-resistant cotton, especially for transgenic double genes （Bt＋CpTI） cotton, in this region. In this study, the potential effects of transgenic Bt＋CpTI cotton on the seasonal abundance of non-target pests and predators were assessed from 2009 to 2011 in Korla, Xinjiang. The results showed that species composition and seasonal abundance of 5 groups of pests and 5 groups of predators were not significantly different between transgenic Bt＋CpTI cotton and non-transgenic cotton every year. It suggests that transgenic Bt＋CpTI cotton per se does not affect the population dynamics of non-target pests and predators on this crop in Xinjiang.

p38 MAPK is a Component of the Signal Transduction Pathway Triggering Cold Stress Response in the MED Cryptic Species of Bemisia tabaci

Cold stress responses help insects to survive under low temperatures that would be lethal otherwise.This phenomenon might contribute to the invasion of some Bemisia tabaci cryptic species from subtropical areas to temperate regions.However,the molecular mechanisms regulating cold stress responses in whitefly are yet unclear.Mitogen-activated protein kinases（MAPKs）which including p38,ERK,and JNK,are well known for their roles in regulating metabolic responses to cold stress in many insects.In this study,we explored the possible roles of the MAPKs in response to low temperature stresses in the Mediterranean cryptic species（the Q-biotype）of the B.tabaci species complex.First,we cloned the p38 and ERK genes from the whitefly cDNA library.Next,we analyzed the activation of MAPKs during cold stress in the Mediterranean cryptic species by immuno-blotting.After cold stress,the level of phospho-p38 increased but no significant change was observed in the phosphorylation of ERK and JNK,thus suggesting that the p38 might be responsible for the defense response to low temperature stress.Furthermore,we demonstrated that：i）3 min chilling at 0°C was sufficient for the activation of p38 MAPK pathway in this whitefly;and ii）the amount of phosphorylated p38 increased significantly in the first 20 min of chilling,reversed by 60 min,and then returned to the original level by 120 min.Taken together,our results suggest that the p38 pathway is important during response to low temperature stress in the Mediterranean cryptic species of the B.tabaci species complex.

Species Exclusion Between an Invasive and an Indigenous Whitefly on Host Plants with Differential Levels of Suitability

The whitefly Bemisia tabaci has risen to international prominence since the 1980s due to the rapid spread around the globe by the two species B and Q within this species complex.The invasion of B has often been associated with the displacement of indigenous whiteflies.As the genetic structure of B.tabaci is diverse,more case studies of the competitive relationships between B and indigenous species of the whitefly species complex will help to understand further the mechanisms underlying the invasion of B.We examined the competitive interactions between B and ZHJ2,a widely distributed indigenous whitefly in Asia,on host plants with differential levels of suitability to the two species in the laboratory,and also tested the effect of insecticide application on the competitive relationships.Three species of plants were tested including cotton,a plant showing similar levels of suitability to both species,squash,a plant showing higher suitability to B than to ZHJ2,and kidney bean,a plant showing higher suitability to ZHJ2 than to B.In the case of no insecticide application,B displaced ZHJ2 on cotton,squash,and kidney bean by the 6th,3rd and 10th generation,respectively.With the application of imidacloprid,the displacement of ZHJ2 by B on cotton occurred by the 5th generation.As the displacement progressed,the proportion of B females increased,and the proportion of ZHJ2 females decreased on cotton and squash.In contrast,on kidney bean the proportion of B females remained unchanged while that of ZHJ2 increased.These results show the strong capacity of the invasive B to displace ZHJ2,and indicate that host plants with differential levels of suitability to the two species may affect the speed but not the trend of displacement and insecticide application may accelerate the process of displacement.

Impact Assessments of Transgenic cry1Ab Rice on the Population Dynamics of Five Non-Target Thrips Species and Their General Predatory Flower Bug in Bt and Non-Bt Rice Fields Using Color Sticky Card Traps

A 2-yr field study was conducted to assess the effects of transgenic japonica rice（KMD1 and KMD2） with a synthetic cry1 Ab gene from Bacillus thuingiensis Berliner on population dynamics and seasonal average densities of five thrips species including Stenchaetothrips biformis（Bagnall）,Frankliniella intonsa（Trybom）,F.tenuicornis（Uzel）,Haplothrips aculeatus（Fabricius）,Haplothrips tritici（Kurd） and their general predatory flower bug,Orius similis Zheng as compared to the parental control rice line using the white,blue and yellow sticky card traps.Population dynamics and seasonal average densities of these five thrips species and their general predatory flower bug were not significantly affected by rice type.Additionally,the white sticky card trap was suggested to be the most suitable for monitoring the population of these five thrips species and their general predator.These results show that our tested Bt rice lines do not interrupt the population of non-target thrips species and their general predatory flower bug in the field,and also cannot result in more occurrence of these thrips species in the rice ecosystem.

Cloning,Tissue Distribution,and Transmembrane Orientation of the Olfactory Co-Receptor Orco from Two Important Lepidopteran Rice Pests,the Leaffolder(Cnaphalocrocis medinalis) and the Striped Stem Borer(Chilo suppressalis)

In insects,the sense of smell is mainly mediated by olfactory receptors（Ors）.Olfactory co-receptor（Orco）,which is coexpressed with the Ors in almost all olfactory receptor neurons（ORNs）,is demonstrated to be an essential component in the insect olfactory system.It can be potential target for developing novel olfactory-disruption strategy to control insect pests.In this study,two full-length cDNA sequences encoding Orcos（CmedOrco and ChsupOrco） were cloned from two Lepidopteran rice pests,the rice leaffolder,Cnaphalocrocis medinalis and the rice striped stem borer,Chilo suppressalis.The amino acid sequences of CmedOrco and ChsupOrco showed high similarity to the previously identified Orcos from other insect species. Bioinformatic prediction and cellular immunofluorescence indicated that CmedOrco and ChsupOrco were both seven-transmembrane proteins with intracellular N-termini and extracellular C-termini.mRNA expression levels of the two Orcos were much higher in male and female antennae than those in non-olfactory tissues,and the ChsupOrco transcripts reached a peak level in adults compared to other life stages.Our results provide a foundation from which it will be possible to elucidate the roles of Orco in moth olfaction and for the development of environment-friendly management strategies of these two rice insect pests.

Characterization of a native whitefly vitellogenin gene cDNA and its expression pattern compared with two invasive whitefly cryptic species

supported by grants from the National Basic Research Program of China （2014CB138404）;the China National Science Fund for Innovative Research Groups of Biological Control （31321063）;the National Basic Research Program of China （973 Program, 2009CB119203）;the National Natural Science Foundation for Young Scientists in China （31101674）

Thrips-mediated impacts from transgenic rice expressing Cry1Ab on ecological fitness of non-target predator Orius tantilus(Hemiptera:Anthocoridae)

Various rice lines have been genetically modified with genes from Bacillus thuringiensis（Bt） to continuously produce Bt insecticidal proteins against lepidopteran larvae. The Bt insecticidal protein constantly expresses in the plants to create an opportunity for non-target herbivores to acquire and convey the protein to their predators or parasitoids across trophic levels. This paper evaluates the effects of Bt rice（namely, Kemindao 1（KMD1） and Kemindao 2（KMD2）） expressing Cry1 Ab as compared to its non-Bt control line, Xiushui 11 on non-target predator Orius tantilus（a generalist predatory anthocorid of thrips） under laboratory and field conditions. To measure several biological parameters such as total nymphal duration and fecundity of this bug, it was reared on thrips and pollens of KMD1 and KMD2 as compared to their control under laboratory conditions. By comparison with the control, Bt rice did not significantly affect main life-history characteristics（total nymphal duration, female adult longevity, oviposition period and fecundity） of this anthocorid preying on Bt rice-fed thrips along with Bt rice pollens, except that the fecundity of this predator for KMD1 was distinctly lower as compared with KMD2 or the control. Enzyme-linked immunosorbent assay（ELISA） results showed that no Cry1 Ab protein was detected in this predator fed on thrips or rice pollen from Bt rice but was in Bt rice pollens. With the beat plate, plastic bag and color trap sampling methods, two-year field monitoring of O. tantilus abundance demonstrated that Bt rice had no significant detrimental effects on the population dynamics and seasonal average densities of this predatory anthocorid as compared with the control. Thus, it is suggested that growing our tested Bt rice（KMD1 and KMD2） producing Cry1 Ab will pose a negligible risk to the anthocorid, O. tantilus.

Species Concepts as Applied to the Whitefly Bemisia tabaci Systematics:How Many Species Are There?

The worldwide distribution and extensive genetic diversity of the whitefly,Bemisia tabaci,has long been recognized.However,the levels of separation within B.tabaci and the nomenclature of the various genetic groups have been a subject of debate.Recent phylogenetic analyses indicate that B.tabaci is a complex composed of 28 morphologically indistinguishable species.In this article,we first review the debate and difficulties associated with B.tabaci＇s taxonomy and systematics,and argue for the need to apply the biological species concept in order to elucidate B.tabaci＇s systematics.We summarize the accumulated genetic and behavioural data on reproductive incompatibilities evident amongst phylogenetic mtCOI groups of B.tabaci.Crossing studies have been conducted with 14 of the 28 putative species covering 54 reciprocal inter-species pairs,and observations on mating behaviour have been conducted for seven species pairs.Data from both crossing trials and behavioural observations indicate a consistent pattern of reproductive isolation among the putative species.We then discuss the technical and conceptual complexities associated with crossing experiments and behavioural observations designed to reveal reproductive incompatibility.Finally,we elaborate on a strategy for further clarifying the pattern of reproductive isolation between B.tabaci groups and propose future research directions on the systematics of this complex.

Genome-wide identification and characterization of HSP gene superfamily in whitefly (Bemisia tabacl)and expression profiling analysis under temperature stress

Heat shock proteins (HSP)are essential molecular chaperones that play important roles in the stress stimulation of insects.Bemisia tabaci,a phloem feeder and invasive species,can cause extensive crop damage through direct feeding and transmission of plant viruses.Here we employed comprehensive genomics approaches to identity HSP superfamily members in the Middle East Asia Minor 1 whitefly genome.In total,we identified 26 Hsp genes,including three Hsp90,17 Hsp70,one Hsp60 and five sHSP (small heat shock protein)genes.The HSP gene superfamily of whitefly is expanded compared with the other five insects surveyed here.The gene structures among the same families are relatively conserved.Meanwhile,the motif compositions and secondary structures of BtHsp proteins were predicted.In addition,quantitative polymerase chain reaction analysis showed that the expression patterns of BtHsp gene superfamily were diverse across different tissues of whiteflies.Most Hsp genes were induced or repressed by thermal stress (40℃)and cold treatment (4℃)in whitefly.Silencing the expression of BtHsp70-6 significantly decreased the survival rate of whitefly under 45℃.All the results showed the Hsps conferred thermo-tolerance or cold-tolerance to whiteflies that protect them from being affected by detrimental temperature conditions.Our observations highlighted the molecular evolutionary properties and the response mechanism to temperature assaults of Hsp genes in whitefly.

Diversity of secondary endosymbionts among different putative species of the whitefly Bemisia tabaci

Endosymbionts are important components of arthropod biology. The white- fly Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae） is a cryptic species complex composed of 〉28 putative species. In addition to the primary endosymbiont Portiera aley- rodidarum, six secondary endosymbionts （S-endosymbionts）, Hamiltonella, Rickettsia, Wolbachia, Cardinium, Arsenophonus and Fritschea, have been identified in B. tabaci thus far. Here, we tested five of the six S-endosymbiont lineages （excluding Fritschea） from 340 whitely individuals representing six putative species from China. Harniltonella was detected only in the two exotic invaders, Middle East-Asia Minor 1 （MEAM 1） and Mediter- ranean （MED）. Rickettsia was absent in Asia II 1 and MED, scarce in Asia II 3 （13%）, but abundant in Asia II 7 （63.2%）, China 1 （84.7%） and MEAM1 （100%）. Wolbachia, Cardinium and Arsenophonus were absent in the invasive MEAM1 and MED but mostly abundant in the native putative species. Furthermore, phylogenetic analyses revealed that some S-endosymbionts have several clades and different B. tabaci putative species can harbor different clades of a given S-endosymbiont, demonstrating further the complexity of S-endosymbionts in B. tabaci. All together, our results demonstrate the variation and diversity of S-endosymbionts in different putative species ofB. tabaci, especially between invasive and native whiteflies.

Temporal changes of symbiont density and host fitness after rifampicin treatment in a whitefly of the Bemisia tabaci species complex

Microbial symbionts are essential or important partners to phloem-feeding insects. Antibiotics have been used to selectively eliminate symbionts from their host insects and establish host lines with or without certain symbionts for investigating functions of the symbionts. In this study, using the antibiotic rifampicin we attempted to selectively eliminate certain symbionts from a population of the Middle East-Asia Minor 1 whitefly of the Bemisia tabaci species complex, which harbors the primary symbiont ＂Candidatus Portiera aleyrodidarum＂ and two secondary symbionts ＂Candidatus Hamiltonella defensa＂ and Rickettsia. Neither the primary nor the secondary symbionts were completely depleted in the adults （F0） that fed for 48 h on a diet treated with rifampicin at concentrations of 1 100/zg/mL. However, both the primary and secondary symbionts were nearly completely depleted in the offspring （F 1） of the rifampicin-treated adults. Although the F1 adults produced some eggs （F2）, most of the eggs failed to hatch and none of them reached the second instar, and consequently the rifampicin-treated whitefly colony vanished at the F2 generation. Interestingly, quantitative polymerase chain reaction assays showed that in the rifampicin-treated whiteflies, the density of the primary symbiont was reduced at an obviously slower pace than the secondary symbionts. Mating experiments between rifampicin-treated and untreated adults demonstrated that the negative effects ofrifampicin on host fitness were expressed when the females were treated by the antibiotic, and whether males were treated or not by the antibiotic had little contribution to the negative effects. These observations indicate that with this whitefly population it is not feasible to selectively eliminate the secondary symbionts using rifampicin without affecting the primary symbiont and establish host lines for experimental studies. However, the extinction of the whitefly colony at the second generation after rifampicin treatment indicates the potential of the antibiotic as a control agent of the whitefly pest.

Molecular characterization and expression profiles of nicotinic acetylcholine receptors in the rice striped stem borer, Chilo suppressalis （Lepidoptera： Crambidae）

Nicotinic acetylcholine receptors （nAChRs） are members of the cys-loop ligand- gated ion channel （cysLGIC） superfamily, mediating fast synaptic cholinergic transmission in the central nervous system in insects. Insect nAChRs are the molecular targets of economically important insecticides, such as neonicotinoids and spinosad. Identification and characterization of the nAChR gene family in the rice striped stem borer, Chilo suppressa[is, could provide beneficial information about this important receptor gene family and contribute to the investigation of the molecular modes of insecticide action and resistance for current and future chemical control strategies. We searched our C. suppressalis transcriptome database using Bombyx mori nAChR sequences in local BLAST searches and obtained the putative nAChR subunit complementary DNAs （cDNAs） via reverse transcription polymerase chain reaction （RT-PCR） and rapid amplification of cDNA ends methods. Similar to B. mori, C. suppressalis possesses 12 nAChR subunits, including nine c^-type and three/%type subunits. Quantitative RT-PCR analysis revealed the expression profiles of the nAChR subunits in various tissues, including the brain, subesophageal ganglion, thoracic ganglion, abdominal ganglion, hemocytes, fat body, foregut, midgut, hindgut and Malpighian tubules. Developmental expression analyses showed clear differential expression of nAChR subunits throughout the C. suppressalis life cycle. The identification of nAChR subunits in this study will provide a foundation for investigating the diverse roles played by nAChRs in C. suppressalis and for exploring specific target sites for chemicals that control agricultural pests while sparing beneficial species

Sequencing and comparison of the Rickettsia genomes from the whitefly Bemisia tabaci Middle East Asia Minor I

The whitefly, Bemisia tabaci, harbors the primary symbiont ＇Candidatus Portiera aleyrodidarum＇ and a variety of secondary symbionts. Among these secondary symbionts, Rickettsia is the only one that can be detected both inside and outside the bacteriomes. Infection with Rickettsia has been reported to influence several aspects of the whitefly biology, such as fitness, sex ratio, virus transmission and resistance to pesticides. However, mechanisms underlying these differences remain unclear, largely due to the lack of genomic information of Rickettsia. In this study, we sequenced the genome of two Rickettsia strains isolated from the Middle East Asia Minor 1 （MEAM1） species of the B. tabaci complex in China and Israel. Both Rickettsia genomes were of high coding den- sity and AT-rich, containing more than 1000 coding sequences, much larger than that of the coexisted primary symbiont, Portiera. Moreover, the two Rickettsia strains isolated from China and Israel shared most of the genes with 100% identity and only nine genes showed sequence differences. The phylogenetic analysis using orthologs shared in the genus, inferred the proximity of Rickettsia in MEAM1 and Rickettsia bellii. Functional analysis revealed that Rickettsia was unable to synthesize amino acids required for complementing the whitefly nutrition. Besides, a type IV secretion system and a number of virulence- related genes were detected in the Rickettsia genome. The presence of virulence-related genes might benefit the symbiotic life of the bacteria, and hint on potential effects of Rickettsia on whiteflies. The genome sequences of Rickettsia provided a basis for further understanding the function of Rickettsia in whiteflies.

Cloning of a putative extracellular Cu/Zn superoxide dismutase and functional differences of superoxide dismutases in invasive and indigenous whiteflies

Superoxide dismutases （SODs） are a group of important antioxidant defense enzymes. In this study, a putative extracellular Cu/Zn superoxide dismutase （ecCuZnSOD） complementary DNA was cloned and characterized from the whitefly, Bemisia tabaci. Quantitative polymerase chain reaction analysis showed that the expression level of BtecCuZnSOD was more than 10-fold higher in the invasive Middle East Asia Minor 1 （MEAM1） than in the native Asia II 3 species of the B. tabaci species complex. After exposure to low temperature （4 ℃）, the expression of Bt-ecCuZnSOD gene was significantly up-regulated in MEAM1 but not in Asia II 3. Furthermore, the expression level ofB. tabaci intracellular CuZnSOD （Bt-icCuZnSOD）, Bt-ecCuZnSOD and mitochondrial MnSOD （Bt-mMnSOD） was compared after transferring MEAM1 and Asia II 3 whiteflies from favorable （cotton） to unfavorable host plants （tobacco）. On cotton, both CuZnSOD genes were expressed at a higher level in MEAM1 compared with Asia II 3. Interestingly, after transferring onto tobacco, the expression of Bt-ecCuZnSOD was significantly induced in Asia II 3 but not in MEAM1. On the other hand, while Bt-mMnSOD was expressed equally in both species on cotton, Bt-mMnSOD messenger RNA was up-regulated in MEAM 1 on tobacco. Consistently, enzymatic activity assays of CuZnSOD and MnSOD demonstrated that CuZnSOD might play an important protective role against oxidative stress in Asia II 3, whereas MnSOD activation was critical for MEAM1 whiteflies during host adaptation. Taken together, our results suggest that the successful invasion ofMEAM 1 is correlated with its constitutive high activity of CuZnSOD and inducible expression of MnSOD under stress conditions.

Impact of a novel Rickettsia symbiont on the life history and virus transmission capacity of its host whitefly(Bemisia tabaci)

Rickettsia consists of some of the most prevalent symbionts of insects and often plays a significant role in the biology of its hosts.Recently,a maternally inherited Torix group Rickettsia,provisionally named as RiTBt,was recorded in a species of notorious pest whitefly,tentatively named as Asia II 1,from the Bemisia tabaci complex.The role of this Rickettsia in the biology of its host is unknown.Here we investigated the impact of RiTBt on the performance and virus transmission capacity of Asia II 1.RiTBt did not significantly affect the life history parameters of the whitefly when the host insect was reared on tobacco,tomato,and cotton,three host plants with relatively low,medium and high suitability to the whitefly.Intriguingly,RiTBt slightly enhanced whitefly transmission of cotton leaf curl Multan virus(CLCuMuV),a virus that is transmitted by the whitefly in the field and has caused extensive damage to cotton production.Specifically,compared with whiteflies without RiTBt,following a 48 h virus acquisition whiteflies with RiTBt had higher titer of virus and showed higher efficiency of virus transmission.A rickettsial secretory protein BtR242 was identified as a putative virus-binding protein,and was observed to interact with the coat protein of CLCuMuV in vitro.Viral infection of the whitefly downregulated gene transcript levels of the BtR242 gene.These observations indicate that RiTBt has limited impact on the biology of the Asia II 1 whitefly,and whether this symbiont has functions in the biology of other host whiteflies warrants future investigation.

Further insight into reproductive incompatibility between putative cryptic species of the Bemisia tabaci whitefly complex

The whitefly Bemisia tabaci （Gennadius） （Hemiptera： Aleyrodidae）, with its global distribution and extensive genetic diversity, is now known to be a complex of over 35 cryptic species. However, a satisfactory resolution of the systematics of this species complex is yet to be achieved. Here, we designed experiments to examine reproductive compatibility among species with different levels of mitochondrial cytochrome oxidase I （mtCOI） divergence. The data show that putative species with mtCOI divergence of 〉 8% between them consistently exhibited complete reproductive isolation. However, two of the putative species, Asia II 9 and Asia II 3, with mtCOI divergence of 4.47% between them, exhibited near complete reproductive compatibility in one direction of their cross, and partial reproductive compatibility in the other direction. Together with some recent reports on this topic from the literature, our data indicates that, while divergence in the mtCOI sequences provides a valid molecular marker for species delimitation in most clades, more genetic markers and more sophisticated molecular phylogeny will be required to achieve adequate delimitation of all species in this whitefly complex. While many attempts have been made to examine the reproductive compatibility among genetic groups of the B. tabaci complex, our study represents the first effort to conduct crossing experiments with putative species that were chosen with considerations of their genetic divergence. In light of the new data, we discuss the best strategy and protocols to conduct further molecular phylogenetic analysis and crossing trials, in order to reveal the overall pattern of reproductive incompatibility among species of this whitefly complex.

FAR gene enables the brown planthopper to walk and jump on water in paddy field

Many insects can live on water and survive being caught in the rain.Current research has shown that insect cuticular hydrocarbons(CHC)confer desiccation resistance to maintain water balance.In this study,we identified a fatty acyl-CoA reductase gene(NlFAR)of the rice brown planthopper,Nilaparvata lugens that is essential for the production of CHCs,and found that NlFAR is essential for N.lugens to walk and jump on water when moving from one rice plant to another in paddy fields.NlFAR was mainly expressed in the integument at the beginning of each molt.Cuticular surface analysis by scanning electron microscopy and characterization of CHC extracts indicated that N.lugens with knockdown of NlFAR using RNA inference(RNAi)had a neater epicuticle layer and a significant decrease in CHC contents.Knockdown of NlFAR did not influence the desiccation resistance of N.lugens,but the ds NlFAR-treated insects were easily adhered and moistened by water droplets or their own secreted honeydew and unable to walk or jump on water.These results suggested that NlFAR is a crucial enzyme for CHC biosynthesis and cuticle waterproofing,but not for water retention of N.lugens,which may provide a potential strategy for pest management.

Transgenic plants expressing the AalT/GNA fusion protein show increased resistance and toxicity to both chewing and sucking pests

The adoption of pest-resistant transgenic plants to reduce yield losses and de- crease pesticide use has been successful. To achieve the goal of controlling both chewing and sucking pests in a given transgenic plant, we generated transgenic tobacco, Arabidopsis, and rice plants expressing the fusion protein, AalT/GNA, in which an insecticidal scor- pion venom neurotoxin （Androctonus australis toxin, AalT） is fused to snowdrop lectin （Galanthus nivalis agglutinin, GNA）. Compared with transgenic tobacco and Arabidop- sis plants expressing AaIT or GNA, transgenic plants expressing AalT/GNA exhibited increased resistance and toxicity to one chewing pest, the cotton bollworm, Helicoverpa armigera. Transgenic tobacco and rice plants expressing AalT/GNA showed increased resistance and toxicity to two sucking pests, the whitefly, Bemisia tabaci, and the rice brown planthopper, Nilaparvata lugens, respectively. Moreover, in the field, transgenic rice plants expressing AalT/GNA exhibited a significant improvement in grain yield when infested with N. lugens. This study shows that expressing the AalT/GNA fusion protein in transgenic plants can be a useful approach for controlling pests, particularly sucking pests which are not susceptible to the toxin in Bt crops.

Differences in mating behavior lead to asymmetric mating interactions and consequential changes in sex ratio between an invasive and an indigenous whitefly

The invasive B whitefly and the indigenous ZHJ2 whitefly in China of the Bemisia tabaci complex represent two previously allopatric cryptic species.Laboratory experiments have shown that the invasive B can displace the indigenous ZHJ2.Here,we observed the mating behavior and mating interactions between B and ZHJ2 to elucidate the behavioral mechanisms underlying their competition.The 2 species are able to mate with each oth-er,although at a significantly lower frequency than that between males and females within the same species.Heterospecifically-mated females produce only male progeny,indicating reproductive isolation.Heterospecific mating had only a marginal effect on reproduction of females in either species.Detailed observations on mating interactions between the 2 species showed that B had higher sexual activity than ZHJ2.B males were more like-ly to interrupt courtships initiated by rival males than ZHJ2 males.Compared with ZHJ2 males,B males were also more likely to successfully interrupt courtships initiated by rival heterospecific males than by males of the same species.In addition,B males guarded B females post-copulation,whereas ZHJ2 males did not.When the 2 species co-occurred,the behavioral differences and interactions between them resulted in an increased propor-tion of females produced in the offspring of B but reduced proportion of females in the progeny of ZHJ2.These asymmetric mating interactions might be an important mechanism underlying the displacement of ZHJ2 by B.Our study shows that reproductive interference might contribute to the competitive exclusion between closely related species during biological invasions.