Altered olfactory receptor neuron responsiveness in rare Ostrinia nubilalis males attracted to the O. furnacalis pheromone blend

Three percent of E-strain Ostrinia nubilalis males fly upwind in response to the Ostrinia furnacalis pheromone blend [a 40:60 ratio of (E)-12-tetradecenyl acetate to (Z)-12-tetradecenyl acetate (E12-14:OAc to Z12-14:OAc)], in addition to their own pheromone blend [a 99:1 ratio of (E)-11-tetradecenyl acetate to (Z)-11-tetradecenyl acetate) (E11-14:OAc to Z11-14:OAc)]. We assessed the olfactory receptor neuron (ORN) responses of these behaviorally "rare" males versus those of normal males. For the three ORNs housed within each sensillum, we tested responsiveness to Z12-14:OAc, E12-14:OAc, Z11-14:OAc, E11-14:OAc, and the behavioral antagonist (Z)-9-tetradecenyl acetate (Z9-14:OAc). Z11-14:OAc, E11-14:OAc, and Z9-14:OAc stimulated ORNs exhibiting distinct small, large, and medium spike sizes, respectively. For rare and normal males, both Z12-14:OAc and E12-14:OAc usually elicited responses from the largest-spiking ORN. In many ORNs of normal males, Z12-14:OAc or E12-14:OAc stimulated the smaller-spiking ORN that is responsive to Z11-14:OAc. In rare males, detectable ORN responses from the smaller-spiking ORN in response to Z12- and E12-14:OAc were virtually non-existent. These differences in ORN tuning in rare males will tend to create an ORN firing ratio between the large- and small-spiking ORNs in response to the O. furnacalis blend that is similar to that elicited by the O. nubilalis blend.     

Foraging for intermittently refuged prey: theory and field observations of a parasitoid

Many insect herbivores feed in concealed locations but become accessible intermittently, creating windows of greater vulnerability to attack, and generating a proportion of the prey population that is readily accessible to foraging natural enemies. We incorporated accessible prey into an extant optimal foraging model, and found that this addition allowed opportunistic exploitation of prey that have already emerged from refugia (the leaving strategy) as a viable strategy, in addition to waiting at refugia for prey to emerge (the waiting strategy). We parameterized the model empirically for the parasitoid Macrocentrus grandii and its host, Ostrinia nubilalis, under field conditions. The model predicted that M. grandii should adopt a leaving strategy when host patch density is high (travel time between patches is short), but a waiting strategy when host patch density is low (travel time between patches is long). Field observations of M. grandii patch tenure were consistent with model predictions, indicating that M. grandii exhibited flexible behaviour based on experience within a foraging bout, and that these behavioural shifts improved foraging efficiency. Behaviour of M. grandii was responsive to heterogeneity in host emergence rates, and appeared to be driven by the relatively small proportion of the host population that became accessible at a fast rate. Therefore understanding forager responses to intermittently refuged prey may require characterization of the behaviour of a subset of the prey population, rather than the average prey individual. The model can potentially be used as a framework for comparative studies across forager taxa, to understand when foragers on intermittently accessible prey should adopt fixed waiting or leaving strategies vs. a flexible strategy that is responsive to the current environment.     

玉米水解糖液体培养灵芝发酵条件的优化

目的：优化液体培养灵芝的发酵条件,提高多糖产量。方法：采用玉米水解糖为主要成分的培养基,通过单因素和正交实验,对赤芝G22菌株液体培养过程中影响多糖产量的发酵温度、摇床转速等工艺条件进行了研究。结果：经极差分析和方差分析确定了多糖高产的最佳发酵条件为：发酵温度27℃、摇床转速170r/min、培养基初始pH值6.5、发酵时间144 h。结论：通过优化液体发酵条件,可显著提高灵芝多糖的产量。在最佳发酵条件下液体培养G22菌株,灵芝总多糖产量由1.851g/L提高到2.439g/L,提高了31.0%。     

Host plant adaptability and proteomic differences of diverse Rhopalosiphum maidis (Fitch) lineages

Corn leaf aphid Rhopalosiphum maidis (Fitch) can feed on various cereal crops and transmit viruses that may cause serious economic losses. To test the impact of both host plant species and age on R. maidis, as well as the proteomic difference of diverse populations, we first investigated the survival and reproduction of six R. maidis populations (i.e., LF, HF, GZ, DY, BJ, and MS) via a direct observation method in the laboratory on 10 and 50 cm high maize seedlings, and 10 cm high barley seedlings. Then a proteomic approach was implemented to identify the differentially expressed proteins from both aphids and endosymbionts of BJ and MS populations. Results indicated that the BJ population performed significantly better than the others on both barley and 50 cm high maize seedlings, while no population could survive on 10 cm high maize seedlings. The proteomic results demonstrated that the expression levels of myosin heavy chain (muscle isoform X12) (spot 781) and peroxidase (spot 1383) were upregulated, while ATP-dependent protease Hsp 100 (spot 2137) from Hamiltonella defensa and protein SYMBAF (spot 2703) from Serratia symbiotica were downregulated in the BJ population when compared to expression levels of the MS population. We hypothesize that the fatalness observed on 10 cm high maize seedlings may be caused by secondary metabolites that are synthesized by the seedlings and the MS population of R. maidis should be more stress-resistant than the BJ population. Our results also provide insights for understanding the interaction between host plants and aphids.     

糯玉米胚乳淀粉粒粒度分布形成的酶学机理

以7个糯玉米品种为材料,测定其籽粒发育过程中淀粉粒粒度分布及淀粉合成相关酶活性的变化,分析两者之间的关系。结果表明,随着籽粒发育,糯玉米淀粉粒平均粒径逐渐增大,可溶性淀粉合成酶(SSS)和淀粉分支酶(SBE)活性呈单峰曲线变化。籽粒发育前期,小淀粉粒(≤7.4μm)所占体积较大;随着籽粒发育,小淀粉粒所占体积减少,大淀粉粒(>7.4μm)所占体积增多;籽粒发育后期,大淀粉粒所占体积较大。相关分析表明, SSS和SBE活性与大淀粉粒体积增大速率和平均粒径增大速率均呈显著或极显著正相关。因此, SSS和SBE是影响糯玉米胚乳淀粉粒粒度分布形成的主要酶, SSS和SBE活性越高,淀粉粒平均粒径越大,大淀粉粒所占体积越多。     

Optimising the capacity of field trials to detect the effect of genetically modified maize on non‐target organisms through longitudinal sampling

To assess risks of cultivation of genetically modified crops (GMCs) on non‐target arthropods (NTAs), field tests are necessary to verify laboratory results and in situations where exposure pathways are very complex and cannot be reproduced in the laboratory. A central concern in the design of field trials for this purpose is whether the tests are capable of detecting differences in the abundance or activity of NTAs in a treated crop in comparison with a non‐treated comparator plot. The detection capacity of a trial depends on the abundance and variability of the taxon, the values assumed for type I (α) and II (β) errors, and the characteristics of the trial and statistical design. To determine the optimal trial layout and statistical analysis, 20 field trials carried out in Spain from 2000 to 2009 to assess risks of GMCs on NTAs were examined with α and β set at 0.05 and 0.20, respectively. In this article we aim to determine the optimal number of sampling dates during a season, or longitudinal samples, in the design of field trials for assessing effects of GM maize on NTAs, and the ones that contribute most to achieving detectable treatment effects (d_c) less than 50% of the mean of the control. Detection capacities are a function of the number of individual samples taken during the season but a high number of samples is rarely justified because gains of repeated sampling can be relatively low. These gains depend primarily on field tests relative experimental variability in individual samplings (i.e. experimental variability relative to the mean of the control in each sampling date) which in turn depends on the sampling method (visual counts, pitfall traps or yellow sticky traps) and the density (or abundance) of the taxon in question. Taxa showing more density (or abundance) have less relative experimental variability. The smaller the experimental variability, the lower the profit of increasing the number of sampling dates. Sticky traps have a good effect detection capacity and need very few sampling dates, whereas visual counts and pitfall traps have a poorer effect detection capacity and need more individual samples to achieve d_c values lower than 50%. In maize field trials, it is recommended to concentrate sampling efforts in certain growth stages; the optimal ones for achieving an acceptable detection capacity are variable but, in general, samples in the first half of the season render better detection capacity than samples in the second half.     

响应面法优化维生素K_2(MK-7)发酵条件

对实验室保藏的一株维生素K2(MK-7)高产菌的摇瓶发酵条件进行优化,结果表明菌体在静置培养状态下比在摇瓶培养状态下能够合成更多的维生素K2;同时发现玉米粉经过高温淀粉酶液化之后非常适合作为合成维生素K2的碳源。最后利用响应面法对发酵培养基中主要因素的最适宜水平及其交互作用进行了研究与探讨,优化后维生素K2产量由7.09 mg·L-1提高到了67.22mg·L-1,高于文献报道值。