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Flexibility and variations in morphological and physiological traits are the key for insect herbivores to adapt to environments. The cotton–melon aphid Aphis gossypii Glover is a polyphagous insect which populations exhibit host specialization. Feeding experience on specific host plants converted host specialization in this aphid. However, adaptive changes of this aphids during the host conversion are still unclear. Here, we examined variations in body length, leg segments, and host preference of the cotton-specialized and cucurbit-specialized aphids, A. gossypii, induced by novel host plants. We found that on the original host plants, body, femur, tibia, and tarsus of the cucurbit-specialized aphids were significantly longer than these of the cotton-specialized aphids. However, feeding on zucchini or cowpea resulted in the short body and leg segments in the cucurbit-specialized aphids, whereas led to the long body and leg segments or no changes in the cotton-specialized aphids, and consequently, the tarsus lengths became equal between the cotton- and cucurbit-specialized aphids. Interestingly, the change trends of the relative lengths of leg segments to body length with the increase of reared generation on zucchini were almost different between the cucurbit-specialized and cotton-specialized aphids, especially the relative length of tarsus, but on cowpea, the trends were similar. Meanwhile, feeding on zucchini altered host preference of the cotton-specialized aphids, but not of the cucurbit-specialized aphids. Novel host plants induce adaptive changes in leg segments and host preference of aphids, suggesting the conversion of host specialization.

Sex ratio bias is common in migratory animals and can affect population structure and reproductive strategies, thereby altering population development. However, little is known about the underlying mechanisms that lead to sex ratio bias in migratory insect populations. In this study, we used Cnaphalocrocis medinalis, a typical migratory pest of rice, to explore this phenomenon. A total of 1,170 moths were collected from searchlight traps during immigration periods in 2015–2018. Females were much more abundant than males each year (total females: total males = 722:448). Sex-based differences in emergence time, take-off behaviour, flight capability and energy reserves were evaluated in a laboratory population. Females emerged 0.78 days earlier than males. In addition, the emigratory propensity and flight capability of female moths were greater than those of male moths, and female moths had more energy reserves than did male moths. These results indicate that female moths migrate earlier and can fly farther than male moths, resulting more female moths in the studied immigratory population.

Endosymbionts play important roles in protecting hosts from environmental stress, such as natural enemies, heat, and toxins. Many insects are infected with the facultative nonessential endosymbionts Wolbachia and Rickettsia, which are the crux in this review, although other relevant symbiont genera will also be treated. Insecticide resistance of hosts can be related to infections with Wolbachia and Rickettsia. These endosymbionts commonly increase host susceptibility to chemical insecticides, but cases of increased resistance also exist. The symbiont-mediated insecticide resistance/susceptibility varies with species of insect, species of symbiont, and chemical compound. Changes in insecticide resistance levels of insects can be associated with fluctuations in population density of endosymbionts. Effects of endosymbionts on host fitness, metabolism, immune system, and gene expression may determine how endosymbionts influence insecticide resistance. A clearer understanding of these interactions can improve our knowledge about drivers of decreasing insecticide resistance.

Behavioral thermoregulation is a key strategy for insects to cope with heat stress. The rice leaf folder Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae) larvae usually fold one leaf to construct a leaf shelter. The larvae are vulnerable to heat stress, and the temperature in summer is often beyond the optimal range of them. Shelters confer protection against environmental stress but unclear whether larvae will alter shelter-building behavior when encountering heat stress. We observed the shelter-building behavior of larvae during and after heat shock, and then examined the shape and structure of shelters. Larvae spent more time in selecting a site and building a shelter during and after heat shock than at the optimal temperature. More than 70% of larvae folded two or three leaves to build a shelter during and after heat shock, but more than 60% of larvae only folded one leaf at the optimal temperature. Larvae built more single-leaf longitudinal shelters at the optimal temperature, but they built more multileaf overlapping shelters during and after heat stress. Larvae constructed a short leaf shelter using a small amount of silk binds when they were exposed to 40°C for 4 h. The rice leaf folder larvae can alter their shelter-building behavior and shelter structure in response to heat stress.

Under ongoing climate warming, both the degree and number of high-temperature events in summer may increase, and behavioural adaptation is an important ecological strategy employed by insects to cope with such events. The rice leaf folder, Cnaphalocrocis medinalis Güenée, is a serious insect pest of rice fields in summer. Population outbreaks have become more frequent in the last ten years. In addition to adult migration, rice leaf folders are thought to have other thermal adaptations. Therefore, the behaviours of larval and adult rice leaf folders, such as leaf folding (making shelter) and habitat selection for pupae and eggs, were observed on rice plants under heat stress. The results showed that larval shelter-making velocities significantly decreased during or after four hours of heat exposure, and shelter size decreased as the temperature increased. Larvae preferred to pupate on young rice leaves at 27°C and middle-aged leaves at 30°C, but they strongly preferred older leaves when reared at 34°C. Female moths generally preferred to oviposit on the top of young leaves, but they preferred the middle and lower leaves for egg deposition when exposed to 36 and 40°C, respectively. Furthermore, more eggs were distributed on the lower surfaces of rice leaves with an increase in heat stress. These behavioural responses of rice leaf folders to heat stress indicate that this pest has great potential to adapt to high temperatures; therefore, the possibility of a population outbreak will remain high despite global warming.

The resistance of the small brown planthopper (SBPH), Laodelphax striatella, to insecticides has been widely found in China, and has posed serious problems to efforts to control the pest. To determine the costs and benefits of resistance, the life tables of chlorpyrifos-resistant and -susceptible strains were constructed at 24 and 30°C. The results showed the resistant SBPH (YN-CPF) had lower fitness at 24°C, but slightly higher fitness at 30°C compared to the susceptible SBPH. Transcriptomic analysis showed there are five heat shock protein genes changed their expression, and the up-regulated genes are LsHsc70-1 and LsHsc70-2. The deduced amino acid sequences of LsHsc70-1 and LsHsc70-2 include three heat shock protein 70 (HSP70) family signatures, but LsHSC70-1 has the conserved HSP70 carboxyl terminal region of the "EEVD" motif, while LsHSC70-2 has the endoplasmic reticulum (ER) retention signal of the "KDEL" motif. The phylogenetic tree further identified LsHsc70-1 has closer evolutionary distances to cytoplasmic/nuclear HSP70s from human and Drosophila melanogaster, while LsHsc70-2 has closer evolutionary distances to HSP70s localized to ER. After treatment at 30-44°C, the expression of LsHsc70-1 and LsHsc70-2 was slightly increased in YN-CPF. These results suggested that LsHsc70-1 and LsHsc70-2 are members of Hsc70 family, localized to the cytosol/nucleus and ER, respectively. The up-regulated expression of these genes may protect the chlorpyrifos-resistant pest against damage under high temperatures, increasing its relative fitness, but the lower relative fitness of this population under optimal temperature may be the trade-off.

Genetic polymorphism and endosymbiont infection are ubiquitous in aphid populations. It has been known that the obligate symbiont Buchnera provides aphids with essential amino acids which cannot be ingested from plant sap. Buchnera often coexists with facultative endosymbionts in aphids. However, it is unclear whether the facultative endosymbionts affect the aphid's amino acid requirements from diet. In this study, we found that the facultative endosymbiont status in populations of the cotton-melon aphid Aphis gossypii was associated with aphid genotype or host plant. The infection frequency of Arsenophonus in aphids living on cotton was significantly higher than that in aphids on cucumber, and cucumber leaves contained higher titers of free amino acids than cotton leaves, especially amino acids Leu, Arg, Ile, Val, and Phe. The net reproductive rates of five aphid genotypes infected with Arsenophonus were not different on the complete-amino-acid diet, but the values were significantly different among seven Arsenophonus-free aphid genotypes. Moreover, the net reproductive rates of aphids on the amino-acid-deficient diet were significantly affected by Arsenophonus infection and aphid genotype. Arsenophonus infection decreased aphid performance on the Phe-free diet but improved performance on the Leu-free diet and did not affect the performance on the Ile-free or Val-free diet. Arsenophonus infections altered aphid requirements for amino acids that were significantly different in cotton and cucumber leaves, suggesting this endosymbiont would modulate the host specialization of this aphid.IMPORTANCE The facultative endosymbiont Arsenophonus plays an important role in regulating reproduction through son killing, enemy resistance, and the dietary breadth of its insect hosts. In this study, we found Arsenophonus could alter aphid performance on the amino-acid-deficient diets. Arsenophonus infection increased aphid requirements for the amino acid Phe, but decreased requirements for the Leu. Cotton and cucumber leaves contained drastically different titers of free amino acids Phe and Leu, and aphids living on these two plants were infected with different incidences of Arsenophonus We hypothesize that host specialization or the host plant range of aphids may be mediated by Arsenophonus.

Wing dimorphism is considered as an adaptive trait of insects. Brown planthoppers (BPHs) Nilaparvata lugens, a serious pest of rice, are either macropterous or brachypterous. Genetic and environmental factors are both likely to control wing morph determination in BPHs, but the hereditary law and genes network are still unknown. Here, we investigated changes in gene expression levels between macropterous and brachypterous BPHs by creating artificially bred morphotype lines. The nearly pure-bred strains of macropterous and brachypterous BPHs were established, and their transcriptomes and gene expression levels were compared. Over ten-thousand differentially expressed genes (DEGs) between macropterous and brachypterous strains were found in the egg, nymph, and adult stages, and the three stages shared 6523 DEGs. The regulation of actin cytoskeleton, focal adhesion, tight junction, and adherens junction pathways were consistently enriched with DEGs across the three stages, whereas insulin signaling pathway, metabolic pathways, vascular smooth muscle contraction, platelet activation, oxytocin signaling pathway, sugar metabolism, and glycolysis/gluconeogenesis were significantly enriched by DEGs in a specific stage. Gene expression trend profiles across three stages were different between the two strains. Eggs, nymphs, and adults from the macropterous strain were distinguishable from the brachypterous based on gene expression levels, and genes that were related to wing morphs were differentially expressed between wing strains or strain &times, stage. A proposed mode based on genes and environments to modulate the wing dimorphism of BPHs was provided.

Migration is a costly strategy in terms of reproduction output. Competition for limited internal resources leads to physiological management of migration-reproduction trade-offs in energy allocation. Migratory insects must choose to determine to allocate energy into reproduction or migration when confronted insufficient energy supply. Although nutrient shortage is known to stimulate insect migration to escape deteriorating habitat, little is known about when and how migratory insects make decisions when confronted by a nutritional shortage. Here Cnaphalocrocis medinalis (Lepidoptera: Pyralidae), a migratory rice pest in eastern Asia, was used to study the effects of starvation on reproductive traits, behavioral traits and energy allocation. The result showed that one or two days&rsquo, starvation before preoviposition did not significantly reduce the fertility (total egg per female laid) and flight capability (flight duration and distance) of both sexes C. medinalis. The preoviposition period was extended significantly only if moths were starved starting on the first day after emergence. Also, take-off percentage of moths starved since their first day increased significantly, and continued to increase even if supplemental nutrients were supplied as honey solution in later days. Moths starved on the first day appeared to allocate or transfer triglycerides into the thorax to maintain the migration process: the quantity of thoracic triglycerides did not differ with age, but abdominal triglycerides decreased with age if starvation continued. These results indicate that the first day post-emergence is a critical period for C. medinalis to decide to migrate or not in response to lack of food. This furthers our understanding of the population dynamics of migratory insects under natural conditions.

Background A polyphagous insect herbivore has a wide range of host plants. However, it has been found that many polyphagous herbivores commonly exhibit a strong preference for a subset of species in their broad host range, and various host biotypes exist in herbivore populations. Nutrition and secondary metabolites in plants affect herbivore preference and performance, but it is still not clear which factors determine the host range and host preference of polyphagous herbivores. Method Cotton-melon aphids, Aphis gossypii Glover, collected from cotton and cucumber crops, were used in this study. The genetic backgrounds of these aphids were detected using microsatellite PCR and six genotypes were evaluated. Performance of these six aphid genotypes on excised leaves and plants of cotton and cucumber seedlings were examined through a reciprocal transplant experiment. In order to detect whether the feeding experience on artificial diet would alter aphid host range, the six genotypes of aphids fed on artificial diet for seven days were transferred onto cotton and cucumber leaves, and then their population growth on these two host plants was surveyed. Results Aphids from cotton and cucumber plants could not colonize the excised leaves and intact plants of cucumber and cotton seedlings, respectively. All six genotypes of aphids collected from cotton and cucumber plants could survive and produce offspring on artificial diet, which lacked plant secondary metabolites. The feeding experience on the artificial diet did not alter the ability of all six genotypes to use their native host plants. However, after feeding on this artificial diet for seven days, two aphid genotypes from cotton and one from cucumber acquired the ability to use both of the excised leaves from cucumber and cotton plants. The two aphid genotypes from cotton conditioned by the feeding experience on artificial diet and then reared on excised cucumber leaves for >12 generations still maintained the ability to use intact cotton plants but did not establish a population on cucumber plants. However, one cucumber genotype conditioned by artificial diet and then reared on excised cotton leaves could use both the intact cotton and cucumber plants, showing that the expansion of host range was mediated by feeding experience. Conclusion Feeding experience on artificial diet induced the expansion of host range of the cucurbit-specialized A. gossypii, and this expansion was genotype-specific. We speculated that feeding on a constant set of host plants in the life cycle of aphids may contribute to the formation of host specialization.

Regiella insecticola is a bacterial endosymbiont in insects that exhibits a negative effect on the fitness of hosts. Thus, it is not clear why this costly endosymbiont can persist in host populations. Here, we tested a hypothesis that the infection pattern and negative roles of the endosymbiont were not constant but environmentally dependent. The grain aphids Sitobion avenae, belonging to different genotypes and infected with Regiella or not, were used in this study. We found that S. avenae populations were infected with Regiella, Hamiltonella defensa, Serratia symbiotica and Rickettsia. The predominant endosymbionts in the aphid populations varied with season. Serratia and Rickettsia were predominant from December to February while Regiella predominated from March to May. The vertical transmission of Regiella was poorer at high temperature, but following conditioning for seven generations, the transmission rate improved. Regiella inhibited the production of winged aphids at 25 °C, but it did not affect winged morph production at the higher temperatures of 28 °C and 31 °C. Regiella infection decreased the intrinsic rate of increase (rm) of aphids at 25 °C and 28 °C. However, at 31 °C, the effect of Regiella on the rm varied depending on the aphid genotype and density. Thus, the negative effects of this endosymbiont on its host were environmentally dependent.

Extreme high-temperature events are the key factor to determine population dynamics of the rice leaf folder,Cnaphalocrocis medinalis(Guenée), in summer. Although we know that adult of this insect can migrate to avoid heat stress, the behavioral response of larva to high temperature is still unclear. Therefore, impacts of high temperature on behavioral traits ofC. medinalisincluding host choice, settling and folding leaf were observed. The results revealed that these behavioral traits were clearly influenced by high temperature. The larvae preferred maize leaves rather than rice and wheat at normal temperature of 27°C, but larvae experienced a higher temperature of 37 or 40°C for 4 h preferred rice leaves rather than maize and wheat. Capacity of young larvae to find host leaves or settle on the upper surface of leaves significantly reduced when they were treated by high temperature. High temperature of 40°C reduced the leaf-folding capacity of the third instar larvae, but no effects were observed on the fourth and fifth instar larvae. Short-term heat acclimation could not improve the capacity of the third instar larvae to make leaf fold under 40°C.

The brown planthopper (BPH) is an important pest in rice. Rice losses due to BPH's damage are often more than 10% of yield. Assessments on loss rates from BPH are now basically dependent on experiential indices. However, early assessments on rice yield losses using hyperspectral data are still rare. In this study, reflectance from rice canopy was measured in net cages after different densities of BPH release. Results showed that reflectance in the near-infrared region (750–1000 nm) from milk grain stage, and in 400–531 nm and 567–705 nm from mature grain stage was closely related to BPH density. These spectral indices: red-edge parameters (λr, Dλr, Sλr), ratio of the maximal reflectance in green (490–560 nm) to minimal reflectance (640–740 nm) in red (RGREEN/RRED), ratio of the near-infrared peak (RNIR) to RRED, normalized difference vegetation index between RNIR and RRED and soil-adjusted vegetation index (SAVI) from both milk and mature grain stages, indicated BPH densities well. As expected, ra...

Buchnera aphidicola is an obligate endosymbiont that provides aphids with several essential nutrients. Though much is known about aphid- Buchnera interactions, the effect of the host plant on Buchnera population size remains unclear. Here we used quantitative PCR (qPCR) techniques to explore the effects of the host plant on Buchnera densities in the cotton-melon aphid, Aphis gossypii . Buchnera titers were significantly higher in populations that had been reared on cucumber for over 10 years than in populations maintained on cotton for a similar length of time. Aphids collected in the wild from hibiscus and zucchini harbored more Buchnera symbionts than those collected from cucumber and cotton. The effect of aphid genotype on the population size of Buchnera depended on the host plant upon which they fed. When aphids from populations maintained on cucumber or cotton were transferred to novel host plants, host survival and Buchnera population size fluctuated markedly for the first two generations before becoming relatively stable in the third and later generations. Host plant extracts from cucumber, pumpkin, zucchini, and cowpea added to artificial diets led to a significant increase in Buchnera titers in the aphids from the population reared on cotton, while plant extracts from cotton and zucchini led to a decrease in Buchnera titers in the aphids reared on cucumber. Gossypol, a secondary metabolite from cotton, suppressed Buchnera populations in populations from both cotton and cucumber, while cucurbitacin from cucurbit plants led to higher densities. Together, the results suggest that host plants influence Buchnera population processes and that this may provide phenotypic plasticity in host plant use for clonal aphids.

Although facultative endosymbionts are now known to protect insect hosts against pathogens and parasitoids, the effects of endosymbionts on insecticide resistance are still unclear. Here we show that Wolbachia are associated with increased resistance to the commonly used insecticide, buprofezin, in the small brown planthopper (Laodelphax striatellus) in some genetic backgrounds while having no effect in other backgrounds. In three Wolbachia-infected lines from experimental buprofezin-resistant strains and one line from a buprofezin-susceptible line established from Chuxiong, Yunnan province, China, susceptibility to buprofezin increased after removal of Wolbachia. An increase in susceptibility was also evident in a Wolbachia-infected line established from a field population in Rugao, Jiangsu province. However, no increase was evident in two field populations from Nanjing and Fengxian, Jiangsu province, China. When Wolbachia was introgressed into different genetic backgrounds, followed by Wolbachia removal, the data pointed to Wolbachia effects that depend on the nuclear background as well as on the Wolbachia strain. However, there was no relationship between Wolbachia density and the component of buprofezin resistance associated with the symbiont. The results suggest that Wolbachia effects associated with chemical resistance are complex and unpredictable, but also that they can be substantial.

Remote sensing end-products related to vegetation have potential applications in monitoring the health of crops. The sensitivity of a spectral index to crop stress determines its application prospect. Our aim in this study was to explore the sensitivity of a ratio vegetation index (RVI) to identify the damage caused by brown planthoppers (BPHs) on rice plants, and to evaluate the potential application of hyperspectral end-products to monitor population size of BPH. Different numbers of the second-instar nymphs were released onto potted rice at the tillering stage. The plants were exposed to BPH for two, four, six, and eight days, and reflectance from the damaged rice was measured using a hyperspectral spectroradiometer. Measurements were done again two, four, and six days after exposure (recover days), and then the spectral index RVI746/670 was compared among rice plants infested with different numbers of BPH. The relationships between RVI746/670, the number of BPH and exposure day were simulated by linear and curve models. BPH damage resulted in a decreased spectral index RVI746/670 of rice plants. RVI746/670 well indicated the damage of rice plants caused by six&ndash, eight BPH nymphs per plant in six&ndash, eight days, but the index could not identify the damage of these nymphs in two days. The RVI746/670 showed a two&ndash, four-day delay to indicate a slight BPH damage. The spectral index RVI746/670 could indicate the physiologic compensation of plants for the feeding of BPH and the post-effect of BPH damage on rice. The RVI746/670 of rice showed a quadratic curve relation with the number of BPH nymphs and a quadratic or linear relation with the exposure day. The recover day had no significant effects on RVI746/670. The RVI746/670 (Y) could be simulated by a quadratic surface model based on the number of BPH (N) and exposure day (T): Y = 3.09427 + 0.59111T + 0.44296N &minus, 0.03683T2 &minus, 0.03035N2 &minus, 0.08188NT (R2 = 0.5228, p &lt, 0.01). In summary, the spectral index RVI746/670 of rice is sensitive to damage caused by BPH.

Physiological response and acclimation to thermal stress is a key strategy of insects to cope with changing climate. The underlying mechanism of heat acclimation in insects is still unclear. Here, the heat selection and transcript level response in the larvae of the rice leaf folder Cnaphalocrocis medinalis Guenee, a serious pest of rice in summer, were studied. The survival and fecundity of larvae during multigenerational heat selection at 39 °C were examined, and heat tolerance and mRNA expression of heat shock protein 70 (Hsp70) and 90 (Hsp90) were examined under heat stress. The results showed that survival and fecundity of larvae increased notably and then kept constant after two or three generations of heat selection. Heat selection improved thermal tolerance of larvae. The Hsp70 mRNA expression of the 3rd-instar larvae increased in all five generations of heat selection, but Hsp90 increased only in the first two generations. The response of Hsp70 to 39 °C heat treatment in the larvae kept at 27 °C was different from the larvae exposed to the conditioning heat treatments, but the response of Hsp 90 was similar. Moreover, the Hsp70 and Hsp90 mRNA expression levels were significantly higher in the heat-acclimated larvae than that in the unacclimated larvae at a comparable duration of exposure to 37 and 41 °C. Selection at a high temperature across multiple generations led larvae to heat acclimation, and Hsp70 and Hsp90 were involved in this acclimation process.

Wolbachia are the most common symbionts in arthropods; antibiotic treatment for eliminating the symbionts from their host is necessary to investigate the functions. Tetracycline antibiotics are widely used to remove endosymbiont Wolbachia from insect hosts. However, very little has been known on the effects of tetracycline on population size of Wolbachia in small brown planthopper (SBPH), Laodelphax striatellus (Fallen), an important insect pest of rice in Asia. Here, we investigated the dynamics of Wolbachia population density in females and males of L. striatellus by real-time fluorescent quantitative PCR method. The Wolbachia density in females and males of L. striatellus all declined sharply after treatment with 2 mg/mL tetracycline for one generation, and continued to decrease to a level which could not be detected by both qPCR and diagnostic PCR after treated for another generation, then maintained at 0 in the following three generations with continuous antibiotic treatment. Wolbachia infection did not recover in L. striatellus after stopping tetracycline treatment for ten generations. This is the first report to precisely monitor the population dynamics of Wolbachia in L. striatellus during successive tetracycline treatment and after that. The results provide a useful method for evaluating the efficiency of artificial operation of endosymbionts.

Potato virus Y (PVY) and Myzus persicae are important pests of tobacco and potato crops. Myzus persicae can transmit PVY in a non-persistent manner. In this study, we investigated whether tobacco plants infected with PVY affected the performance and behavior of M. persicae by comparing growth, reproduction, and stylet penetration behaviors of M. persicae on PVY-infected vs. noninfected plants. We found that body and cornicle length, body and head width, and distance between compound eyes were significantly smaller in adult M. persicae reared on infected tobacco plants. Electrical penetration graph (EPG) recordings showed that the time spent on the plant before the first probe and the duration of the first probe increased significantly when M. persicae fed on PVY-infected rather than noninfected plants. The number of probes made by aphids on infected plants in the first hour was also greater than on healthy plants. Furthermore, M. persicae had a slightly higher net reproductive rate (R 0) when on infected tobacco plants than on noninfected plants. In summary, our data indicated that PVY infection had a negative effect on the growth of M. persicae. We suggest that the increased stylet penetration behavior of M. persicae on infected plants may be associated with increased virus acquisition and transmission.

The endosymbionts Wolbachia and Rickettsia have been shown to be correlated with the insecticide resistance of mosquito and whitefly. The small brown planthopper (SBPH), Laodelphax striatellus, harbours many species of endosymbionts, and has developed a high resistance to buprofezin in China. In this study, we examined the species and the infection incidences of endosymbionts in a buprofezin-resistant (BR) strain, a buprofezin-susceptible (BS) strain, and the BR strain after exposure to buprofezin, and we also investigated the change in buprofezin susceptibility after removal of Wolbachia from the BR strain. The results showed that Wolbachia infection incidences were 100% in both the BR and BS strains, but the Wolbachia density in the BR strain was significantly higher than that in the BS strain. There were no significant differences in Arsenophonus infection incidence between the two strains. However, the infection incidence of Serratia and double infection incidence of Serratia + Wolbachia in the BR strain were significantly higher than that in the BS strain. After the BR strain was exposed to 1200 mg/L buprofezin, the infection incidence of Arsenophonus in the surviving individuals increased, and the infection rate of Serratia did not differ, but the double infection incidence of Serratia + Wolbachia decreased. And when a Wolbachia-infected line originating from the BR strain was cleared of Wolbachia, its susceptibility to buprofezin increased. The results suggest that Serratia and Wolbachia infection might improve the buprofezin resistance of SBPH.

Polyphagous cotton-melon aphid populations usually comprise cotton- and cucurbit-specialized biotypes. Host-specialized aphids are prone to food shortages. Cucumber, the favourite food of cucurbit-specialized aphids, is usually absent during autumn and winter in Nanjing, China. Therefore, suboptimal host plants act as refuges and govern the population dynamics of this aphid. The species, growth stages and leaf ages of host plants that cotton- and cucurbit-specialized aphids potentially could use were explored in this study. Cotton-specialized aphids were found to use wild chrysanthemum, potato, zucchini, pumpkin and flowering cucumber besides cotton, whilst cucurbit-specialized aphids were able to utilize potato, zucchini, pumpkin and mature cotton besides cucumber. The population dynamics and genotype frequencies of aphids on hibiscus, cotton, zucchini, cucumber and pumpkin showed that cotton-melon aphids on cucumber could transfer onto mature cotton. Aphids on zucchini shared microsatellite genotypes with aphids on cotton and cucumber. The predominant genotype of aphids on cotton was found on hibiscus, but the predominant genotype on cucumber was not found on hibiscus. Host-specialized aphids clearly have refuges during food shortages. Hibiscus is an overwintering host for cotton-specialized aphids but not for cucurbit-aphids. Removing refuges or managing aphids on refuges could potentially be an effective method to control cotton-melon aphids.

Reflectance and SPAD readings were measured in rice grown under different nitrogen fertilizer rates and infested with different numbers of brown planthopper (BPH), Nilaparvata lugens, to assess the relationships among these variables. The results showed that SPAD readings and reflectance from rice were significantly affected by BPH infestations and nitrogen fertilizer rates, whereas there was no interaction between the two factors. SPAD readings and reflectance decreased as BPH infestations increased but they increased as nitrogen fertilizer rates were increased. SPAD readings varied with position of leaf on the same stem of rice. The fourth and fifth leaves were more sensitive to BPH infestations than the first and second regardless of application rates of urea. The ratio indices of SPAD readings of the fourth to first leaf (RSPAD4/1), and fourth to second leaf (RSPAD4/2) were significantly related to BPH infestations, and they were relatively independent of nitrogen fertilizer rates in the single stem rice. The spectral reflectance from rice canopy significantly decreased in the near-infrared wavelength range as BPH infestations increased. The modified chlorophyll absorption ratio index (MCARI710) was found more suitable to relate the numbers of BPH under different nitrogen fertilizer rates and durations of BPH infestation. The main effects of BPH infestations on SPAD reading and reflectance indices were consistent regardless of nitrogen application rates. Therefore, SPAD reading and spectral indices have potential to detect BPH infestations in rice fields.

Aphis gossypii Glover shows obvious host specialization, with cucurbit- and cotton-specialized biotypes or host races in many regions. Because its annual natal host crops senesce earlier the cucurbit-specialized biotype may suffer food deficiency. The method this biotype uses to overcome this challenge is still poorly understood. In order to understand the potential of the cucurbit-specialized biotype aphids in host shift and usage, the performance of this biotype on cotton (Gossypium hirsutum), a common but poor quality host plant, was explored in this study. The cucurbit-specialized aphids could establish populations on cotton only when these plants had at least nine leaves, and subsequent populations developed rather slowly. The presence of whitefly populations on cotton improved the success rate of cucurbit-specialized aphids. The cucurbit-specialized aphids were mainly distributed on the older leaves of cotton, with only a few settling on the upper leaves. The cucurbit-specialized aphids reared on cotton for 40, 54 and 61 days still maintained strong preference for their natal host plant, cucumber (Cucumis sativus), rather than cotton, and their net reproductive rates and intrinsic rates of natural increase were dramatically lower when they were transferred onto new six-leaf cotton plants or detached leaves. Therefore, we concluded that the cucurbit-specialized aphids have the potential to utilize mature or whitefly-stressed cotton plants, but that this feeding experience on cotton did not alter their specialization for cucurbits. Some cotton plants could act as a temporary host for the cucurbit-specialized aphids to overcome food deficiency arising from senescing cucurbits.

In order to understand the continuous defense reactions of host plants against insect attack, a tobacco variety G140 was infested by tobacco aphid Myzus persicae for 2 h to 5 d. The changes of transmembrane ionic fluxes (Ca2+) and hydrogen peroxide (H2O2) were detected by the technique of noninvasive micro-test and their relationship was further studied. It was found that H2O2 accumulation depended on Ca2+ influx. Ca2+ flux exhibited a strong influx at all infestation periods by aphids, while H2O2 showed an efflux behavior. The slight variation tendency of Ca2+ influx and H2O2 efflux was consistent. The activities of the corresponding defense proteins, peroxidase (POD) and catalase (CAT) enzyme, were enhanced to respond to the insect attacks, much higher than those tobacco in control. The Ca2+ influx and H2O2 efflux, as well as the activities of POD and CAT enzymes, were increased in a long period of aphid feeding. It indicated that a continuous physiological response of tobacco to aphid infestation could...

There is ample evidence that insecticide resistance causes fitness costs and benefits in pests, while the impact of insecticide resistance on thermotolerance of pests is mostly unclear. The Laodelphax striatellus (Fallen), is an important rice insect pest, which has developed resistance to buprofezin in China. Here, we investigated differences in heat tolerance and cold tolerance among L. striatellus lines with variable buprofezin resistance. The lethal time for 50% of the individuals to die (LT50) at 40 °C increased with an increase in buprofezin resistance level, whereas both the survival rate under -22 °C and the supercooling point of planthoppers did not differ significantly between resistant and susceptible strains. The metabolic enzyme carboxylesterase was found to have an association with buprofezin resistance. Our research showed that buprofezin resistance was positively related with heat tolerance in L. striatellus, but it had no effect on cold tolerance. Insecticide resistance in L. striatellus may therefore have broader implications for the ecology of L. striatellus, and the management of buprofezin resistance in this pest may be challenging.

The rice leaf folder, Cnaphalocrocis medinalis (Guenee), will frequently be under heat stress because of global warming. The young larvae would be liable to heat exposure owing to inability to make leaf fold for hiding themselves. Consequently, their heat tolerance might be closely related to population outbreak in summer. Therefore, the heat tolerance of the first-instar larvae was examined in this study. The results showed that the heat tolerance of young larvae was lower than that of the older ones. Survival rates of the first-instar larvae were more than 60% on exposure to 39°C for 5 h per day for 3 successive days, but it dropped to below 20% on exposure to 41°C for 5 h per day for 2 successive days. The first-instar larvae exposed to 39°C for less than 8 h per day for 1, 2, and 3 successive days exhibited similar rates of pupation and adult emergence, fecundity, and egg hatchability as the control. High temperature of 39°C influenced the first-instar larvae on a small scale, but 41°C influenced greatly. Young larvae of the rice leaf folder can tolerate short-term heat stress in the present summer, and population outbreaks might not be seriously restricted to global warming.

The reflectance from rice (Oryza sativa L.) leaves and canopy damaged by rice leaf folder (RLF), Cnaphalocrocis medinalis (Guenee) was studied at the booting stage in order to establish a monitoring method for RLF based on hyperspectral data. The results showed that reflectance from rice leaves significantly decreased in the green (530-570nm) and near infrared (700-1000nm) regions, and significantly increased in the blue (450-520nm) and red (580-700nm) regions as the leaf-roll rate of rice increased. Reflectance from rice canopy significantly decreased in the spectral regions from 737 to 1000nm as the infestation scale of RLF increased, and the most correlation appeared at 938nm. Seven spectral regions 503-521, 526-545, 550-568, 581-606, 688-699, 703-715, and 722-770nm at leaf-level, and one region 747-754nm at canopy-level were found to be sensitive bands to exhibit the damage severity in rice by RLF. The position of the red edge peak remarkably moved to blue region, and the amplitude and area of the red edge significantly decreased when rice leaves were severely infected by RLF. Thirty-eight spectral indices at leaf-level and 29 indices at canopy-level were found to be sensitive to leaf-roll rate and infestation scale in rice, respectively. The linear regression models were built to detect the leaf-roll rate (0.0-1.0) and infestation scale (0-5) in rice using leaf- and canopy-level reflectance data. The root mean square error of the model was only 0.059 and 0.22 for the leaf-roll rate and infestation scale, respectively. These results suggested that the hyperspectral reflectance was potential to detect RLF damage severity in rice.

The single‐locus rice blast resistance gene Pi36 is of the coiled‐coil NBS‐LRR (nucleotide binding site–leucine‐rich repeat) type. We have investigated its evolution by resequencing a set of haplotypes (six ssp. indica and four ssp. japonica cultivars and three wild rice accessions) both within and outside the gene’s coding region. It was found that the average nucleotide diversity was ∼4.5%, characteristic of an intermediately diversified pattern. The Ka/Ks ratio and Tajima’s D test were used to show that the gene’s evolution reflects a mixture of purifying and balancing selection. In all, 186 significant gene conversion events were identified across the full coding region, suggesting that gene conversion has also been an important driver of sequence diversification.

ClC-4 is closely related to ClC-5, a member of the ClC family of transporters and channels. Unlike ClC-5, for which a role in the regulation of endosomal function was well established, the cellular function of ClC-4 was uncertain. In the present study, we tested for a specific role for ClC-4 in recycling endosomes by comparing transferrin (Tfn) receptor function in primary cell lines generated from ClC-4-null mice and their wild-type siblings. We found that endosomal pH is relatively alkaline and receptor-mediated uptake of Tfn is reduced in ClC-4-null fibroblasts. Surprisingly, this reduction in Tfn uptake occurs, despite a minor increase in the total surface expression of the Tfn receptor in ClC-4-null fibroblasts. As impaired Tfn uptake by ClC-4-null fibroblasts could be rescued to wild-type levels by addition of the iron chelator: desoxiferramine, the primary defect in these cells is related to the failure of iron to dissociate from Tfn, a pH-dependent event in endosomes that precedes the dissociation of Tfn from its receptor at the cell surface. Interestingly, ClC-4 depletion had no effect on epidermal growth factor receptor (EGFR) trafficking to lysosomes for degradation pointing to its specific role in recycling endosomes. These observations provide direct evidence supporting an essential role for ClC-4 in the modulation of Tfn receptor accessibility at the cell surface through its role in endosomal acidification.

Embryo sac abortion is one of the major reasons for sterility in indica/japonica hybrids in rice. To clarify the causal mechanism of embryo sac abortion, we studied the female gametophyte development in two indica/japonica hybrids via an eosin B staining procedure for embryo sac scanning using confocal laser scanning microscope. Different types of abnormalities occurred during megasporogenesis and megagametogenesis were demonstrated. The earliest abnormality was observed in the megasporocyte. A lot of the chalazal-most megaspores were degenerated before the mono-nucleate embryo sac stage. Disordered positioning of nucleus and abnormal nucellus tissue were characteristics of the abnormal female gametes from the mono-nucleate to four-nucleate embryo sac stages. The abnormalities that occurred from the early stage of the eight-nucleate embryo sac development to the mature embryo sac stage were characterized by smaller sizes and wrinkled antipodals. Asynchronous nuclear migration, abnormal positioning of nucleus, and degeneration of egg apparatus were also found at the eight-nucleate embryo sac stage. The abnormalities that occurred during female gametophyte development resulted in five major types of abnormal embryo sacs. These abnormal embryo sacs led to abnormal fertilization. Hand pollination using normal pollens on the spikelets during anthesis showed that normal pollens could not exclude the effect of abnormal embryo sac on seed setting.

The progress of research on transferring elite genes from non-AA genome wild rice into Oryza sativa through interspecific hybridization are in three respects, that is, breeding monosomic alien addition lines (MAALs), constructing introgression lines (ILs) and analyzing the heredity of the characters and mapping the related genes. There are serious reproductive barriers, mainly incrossability and hybrid sterility, in the interspecific hybridization of O. sativa with non-AA genome wild rice. These are the ‘bottleneck’ for transferring elite genes from wild rice to O. sativa. Combining traditional crossing method with biotechnique is a reliable way to overcome the reproductive barriers and to improve the utilizing efficiency of non-AA genome wild rice.

Although distinct host specialization is observed for the cotton-melon aphid (Aphis gossypii Glover) on cotton and cucurbit plants, it is still ambiguous whether the specialization is altered by experience on a novel host plant. Here the performance of cotton and cucurbit-specialized aphids, A. gossypii on novel host plants was studied by a host-selection test and by the life-table method. The two host-specialized aphids cannot survive and establish populations after reciprocal host transfers. They have ability to recognize the host plants on which they were reared, and escape behavior from novel hosts was observed. Interestingly, the cotton and cucurbit-specialized aphids survive and reproduce normally on hibiscus (Hibiscus syriacus), a main overwintering host plant, and host-fidelity of A. gossypii to cucurbit plants is altered by feeding and living experience on hibiscus, which confers the same capacity to use cotton and cucumber on to the cucurbit-specialized population, but host-fidelity to cotton is not altered and the fitness of the cotton specialized population to cucumber is still poorer. A. gossypii from hibiscus has a significant preference for cotton to cucumber in the host-selection process, and none stays on cucumber more than 20 h after transfer. The results presented imply that cucurbit-specialized aphids might not return to an overwintering host plant (hibiscus) in wild fields, so host conservatism to cucurbit plants is maintained. The potential of cucurbit-specialized aphids of A. gossypii to use cotton plants, intermediated by experience on hibiscus, suggests that the specialized host-plant performance of phytophagous insects is not wholly conservative.

Although there have been some investigations into the effects of insecticide on the level of fluctuating asymmetry (FA) of adult damselflies, the cooperative effects of environmental factors on FA of larval damselflies were known little. This paper explored effects of exposure to temperature and pesticide on larval development of the damselfly Copera annulata (Selys). A conventional life history trait (mortality) and developmental instability (estimated by calculating fluctuating asymmetry of bilaterally symmetrical structures) were used to measure stresses in this paper. The results showed that temperature and different concentrations of pesticide produced significant effects only on developmental stability of some characters. The FA values of three traits decreased at lower concentrations, then increased slowly with increased insecticide doses. The FA values of four traits decreased slowly with increased temperatures. However, the interaction between different concentrations of insecticide and temperature was complicated and only produced significant effects on five traits. Insecticide treatment did not significantly affect mortality of the larvae of damselfly. However, mortality was significantly positively associated with temperature. There were significantly negative associations between mortality and the FA values of three traits. These results may be caused by higher mortality and short rearing time although we did not find the significant effects of concentrations on mortality. Therefore, we speculate FA may be induced if larval damselflies were treated during longer term and FA has potential as a more specific bioindicator of stresses if we guarantee enough longer rearing time without higher mortality under stressful environment.

Polyploidy, or whole-genome duplication (WGD), serves as a key innovation in plant evolution and is an important genomic feature for all eukaryotes. Neopolyploids have to overcome difficulties in meiosis, genomic alterations, changes of gene expression, and epigenomic reorganization. However, the underlying mechanisms for these processes are poorly understood. One of the most interesting aspects is that genome doubling events increase the dosage of all genes. Unlike allopolyploids entangled by both hybridization and polyploidization, autopolyploids, especially artificial lines, in relatively uniform genetic background offer a model system to understand mechanisms of genome-dosage effects. To investigate DNA methylation effects in response to WGD rather than hybridization, we produced autotetraploid rice with its diploid donor, Oryza sativa ssp. indica cv. Aijiaonante, both of which were independently self-pollinated over 48 generations, and generated and compared their comprehensive transcriptomes, base pair-resolution methylomes, and siRNAomes. DNA methylation variation of transposable elements (TEs) was observed as widespread in autotetraploid rice, in which hypermethylation of class II DNA transposons was predominantly noted in CHG and CHH contexts. This was accompanied by changes of 24-nt siRNA abundance, indicating the role of the RNA-directed DNA methylation pathway. Our results showed that the increased methylation state of class II TEs may suppress the expression of neighboring genes in autotetraploid rice that has obtained double alleles, leading to no significant differences in transcriptome alterations for most genes from its diploid donor. Collectively, our findings suggest that chromosome doubling induces methylation variation in TEs that affect gene expression and may become a "genome shock" response factor to help neoautopolyploids adapt to genome-dosage effects.

Three new indole alkaloids, 11,12-de(methylenedioxy)danuphylline (1), methyl (2 beta,11 beta,12 beta,19 alpha)-6,7-didehydro-8,21-dioxo-11,21-cycloaspidospermidine-2-carboxylate (2), and (2 beta,5 beta)-aspidofractinin-16-ol (3) were isolated from Kopsia officinalis, together with 16 known compounds. Their structures were determined by spectroscopic methods. The isolated known compound (-)-12-methoxykopsinaline displayed antimanic effects in Drosophila, with an IC50 value of 12.5 mu g/ml.

1. Transgenic crops have shown great promise for the control of target pest insects, but in some cases they can also influence non-target species. This study investigated the impact of Bt and Bt+CpTI transgenic cottons on the non-target cotton aphid, Aphis gossypii Glover, by comparing life-table parameters, feeding behaviour, and the fluctuating asymmetry of morphological traits of aphids reared on transgenic cotton and those on untransformed control plants. 2. Aphids on the Bt+CpTI cotton showed a shorter reproductive duration and maximum lifespan, lower survival rates and potential maximum fecundity, and an earlier occurrence of peak daily mortality in the first or second generation. However, the aphid population soon developed fitness and overcame the negative effect in the second or third generation. The aphids on the Bt cotton had significantly longer reproductive durations in the first generation, higher survival rates in the third generation, and apparently larger potential maximum fecundity in all three generations. 3. The percentages of accumulated duration of feeding waveforms E1 and E2 were significantly lower in aphids on the Bt+CpTI cotton than in those on the Bt or control cotton, whereas the frequencies of moving and finding feeding sites, and probe behaviour were significantly higher. 4. Fluctuating asymmetry in three morphological characters of aphids reared on transgenic and control cotton was detected. The fluctuating asymmetry value of the third segment of antenna in aphids on Bt+CpTI cotton was significantly higher than that of aphids on Bt or control cotton. Based on the fluctuating asymmetry value, the stress of cotton on the aphids could be ranked as Bt+CpTI cotton > Bt cotton > control cotton.

Temperature is a key environmental factor in determining the population size of Cnaphalocrocis medinalis in summer. High temperatures inhibit survival, development and fecundity of this insect. However, biological responses of female and male adults to heat shock, and physiological mechanism of high temperature suppressing population development are still ambiguous. We experimentally tested the impact of heat shock (5 h day−1) on biological traits, spermatogenesis and sperm transfer of adults of C. medinalis. The result showed that heat exposure to 39 and 40 °C for 5 h reduced longevity and copulation frequency of adults, and hatchability of eggs. Immediate survival rate of males was lower than that of females after 3 days of exposure to 41 °C. The oviposition period, copulation frequency, fecundity of adults and hatchability of eggs were significantly lower when male adults were exposed to 40 or 41 °C for 3 days. Heat shock decreased frequency and success rate of mating when males were exposed, and it also resulted in postponement of mating behaviour and prolongation of mating duration as both the female and male adults were exposed. Heat shock did not affect spermatogenesis, but significantly inhibited sperms maturation. Moreover, males could not ejaculate sperm into females during copulation when these male moths received heat shock. Heat shock remarkably suppressed mating behaviour and sperm transfer, which led to a dramatic decline of rice leaf folder populations.

Muyingle is a new type of health food prepared from marine organisms. The mammotropic action of Muyingle was investigated by studying its effect on mammary glands and pituitary glands of lactating mice and the survival rate of suckling mice. The results showed that the mammotropic action of Muyingle was very effective. The survival rates of suckling mice were 92.90% for the treated group and 0 for the control group (p

Host specialization is a ubiquitous character of phytophagous insects. The polyphagous population is usually composed of some subpopulations that can use only a few closely related plants. Cotton-melon aphids, Aphis gossypii Glover exhibited strong host specialization, and the cotton- and cucurbits-specialized biotypes had been clearly identified. However, the experimental work that addressed the roles of plant species in determining diet breadth of phytophagous insects is rare. In the present study, we took the artificial host transfer method to assess the role of two special plants, zucchini Cucurbita zucchini L. and cowpea Vigna unguiculata (Linn.) Walp, in regulating diet breadth of cotton- and cucurbits-specialized A. gossypii collected from cotton and cucumber fields and reared separately on the native host plant for ten years. The results showed that the cotton-specialized aphids did not directly use cucumber whereas the cucurbits-specialized did not use cotton regardless of the coexistence or separation of cotton and cucumber plants. Neither of the cotton- and cucurbits-specialized aphids could use capsicum Capsicum annuum, eggplant Solanum melongenahttp://en.wikipedia.org/wiki/Carolus_Linnaeus, tomato Solanum lycopersicum, maize Zea mayshttp://en.wikipedia.org/wiki/Carl_Linnaeus, and radish Raphanus sativus, however, both of them could use zucchini and cowpea. Moreover, the feeding experience on zucchini led the cotton-specialized aphids to use cucumber well and finally to be transformed into the cucurbits-specialized biotype. The short-term feeding experience on cowpea resulted in the diet breadth expansion of the cucurbits-specialized aphids to use cotton. On the other hand, the diet breadth expansion of the cucurbits- and cotton-specialized aphids was only realized by different species of plant. It concluded that the special host plant did induce the conversion of feeding habits in the cotton- and cucurbits-specialized aphids, and consequently broke the host specialization. The plant species is an underlying factor to determine the diet breadth of phytophagous insects.

Variation in the reproductive mode of melon aphid Aphis gossypii Glover occurred on the large geographic scale, but the performance of different reproductive modes to use host plant is poorly understood. Life tables of melon aphid population that undergo the anholocyclic, androcyclic, and intermediate reproductive mode were conducted on different host plants. The results showed that the anholocyclic and androcyclic strains could become adults and produce offspring on cotton Gossypium hirsutum L., whereas the intermediate strain could not. The survival rate, net reproductive rate (R(0)), and intrinsic rate of natural increase (r(m)) of the androcyclic strain on cotton were significantly greater than that of the anholocyclic strain. The three strains could aptly use cucurbits host plants including cucumber Cucumis sativa L., pumpkin Cucurbita moschata (Duchesne ex Lam.), and zucchini Cucurbita pepo L.; survival rate and R(0) were not significantly different on these two host plants. Moreover, the r(m) of the anholocyclic strain on cucumber and the androcyclic strain on pumpkin and zucchini were significantly greater than that of the other two strains. The abilities of the three strains to use a host plant were flexible, because their r(m) on pumpkin or zucchini became equal after rearing for four successive generations; furthermore, the intermediate strain attained the ability to use cotton, and the performance of anholocyclic and intermediate strains to use cotton also significantly increased after feeding on pumpkin or zucchini for one or three generations. It was concluded that the reproductive mode and feeding experience affected the performance of melon aphid to use a host plant.

Oryza meyeriana Baill (GG genome) is a precious germplasm in the tertiary gene pool of cultivated rice (AA genome), and possesses important traits such as resistance and tolerance to biotic and abiotic stress. However, interspecific crossability barrier, a critical bottleneck restricting genes transfer from O. meyeriana to cultivars has led to no hybrids through conventional reproduction. Therefore, the reasons underlying incrossability were investigated in the present report. The results showed that: (i) at 3-7 d after pollination (DAP), many hybrid embryos degenerated at the earlier globular-shaped stage, and could not develop into the later pear-shaped stage. Meanwhile, free endosperm nuclei started to degenerate at 1 DAP, and cellular endosperm could not form at 3 DAP, leading to nutrition starvation for young embryo development; (ii) at 11-13 DAP, almost all hybrid ovaries aborted. Even though 72.22% of hybrid young embryos were produced in the interspecific hybridization between O. sativa and O. meyeriana, young embryos were not able to further develop into hybrid plantlets via culturing in vitro. The main reason for the incrossability was hybrid embryo inviability, presenting as embryo development stagnation and degeneration since 3 DAP. Some possible approaches to overcome the crossability barriers in the interspecific hybridization between O. sativa and O. meyeriana are discussed.

The female-biased infection of facultative symbionts has been found in Bemisia tabaci; however, whether there are any differences in tomato yellow leaf curl virus (TYLCV) and obligate symbiont infection rates between females and males is unknown. Determining whether such differences exist would be very important for understanding the spread of the plant virus and of the symbionts. We compared both symbiont infection types, including obligate and facultative symbionts, and the rates of TYLCV infection in both sexes in five field populations from Jiangsu Province, China. The obligate symbiont Portiera aleyrodidarum was not found in every whitefly tested. In all tested populations, more females than males were found to harbor P. aleyrodidarum; and more females than males also harbored Hamiltonella defense, the most common facultative symbiont as well as Cardinium. In addition to female-biased symbiont infections, there were also female-biased TYLCV infections, and the infection frequencies of this plant virus in females were higher than those in males. Taken together, these results suggested that both the female-biased symbiont infections and female-biased TYLCV infections promoted the rapid spread of TYLCV in China.

AIM: To study the function of a-fetoprotein (AFP) in SMMC-7721 hepatoma cells. METHODS: A hairpin siRNA expressing plasmid pSilencer3.0-H1-afp was constructed andtransfected into SMMC-7721 cells with Lipofectamine 2000. The expression of AFP was monitored by real-time RT-PCR and immunoassays, its effect on SMMC-7721 cell proliferation and cell death was detected by MTT and fluorescence- activated cell sorter (FACS). RESULTS: The AFP-siRNA expressing plasmid downregulated the expression of AFP obviously (about 34%), and inhibited SMMC-7721 cell proliferation, but did not induce apoptosis. CONCLUSION: Downregulation of AFP siRNA inhibits proliferation of SMMC-7721 cells, but cannot cause apoptosis.

Background Wingless gene (Wg) plays a fundamental role in regulating the segment polarity and wing imaginal discs of insects. The rice planthoppers have an obvious wing dimorphism, and the long- and short-winged forms exist normally in natural populations. However, the molecular characteristics and functions of Wg in rice planthoppers are poorly understood, and the relationship between expression level of Wg and wing dimorphism has not been clarified. Results In this study, wingless gene (Wg) was cloned from three species of rice planthopper, Sogatella furcifera, Laodelphgax striatellus and Nilaparvata lugens, and its characteristics and role in determining the wing dimorphism of S. furcifera were explored. The results showed that only three different amino acid residuals encoded by Wg were found between S. furcifera and L. striatellus, but more than 10 residuals in N. lugens were different with L. striatellus and S. furcifera. The sequences of amino acids encoded by Wg showed a high degree of identity between these three species of rice planthopper that belong to the same family, Delphacidae. The macropterous and brachypterous lineages of S. furcifera were established by selection experiment. The Wg mRNA expression levels in nymphs were significantly higher in the macropterous lineage than in the brachypterous lineage of S. furcifera. In macropterous adults, the Wg was expressed mainly in wings and legs, and less in body segments. Ingestion of 100 ng/μL double-stranded RNA of Wg from second instar nymphs led to a significant decrease of expression level of Wg during nymphal stage and of body weight of subsequent adults. Moreover, RNAi of Wg resulted in significantly shorter and deformative wings, including shrunken and unfolded wings. Conclusion Wg has high degree of identity among three species of rice planthopper. Wg is involved in the development and growth of wings in S. furcifera. Expression level of Wg during the nymphal stage manipulates the size and pattern of wings in S. furcifera.