Energy Transfer and Exciton Relaxation in B880-B800-RC Complex through Two-Dimensional Electronic Spectroscopy.

The light-harvesting (LH) and reaction center (RC) core complex of purple bacterium Roseiflexus castenholzii, B880-B800-RC, are different from those of the typical photosynthetic unit, (B850-B800)x-B880-RC. To investigate the excitation flowing dynamics in this unique complex, two-dimensional electronic spectroscopy is employed. The obtained time constants for the exciton relaxation in B880, exciton relaxation in B800, B800 → B880 energy transfer (EET), and B880 → closed RC EET are 43 fs, 177 fs, 1.9 ps, and 205 ps, respectively. These time constants result in an overall EET efficiency similar to that of the typical photosynthetic unit. Analysis of the oscillatory signals reveals that while several vibronic coherences are involved in the exciton relaxation process, only one prominent vibronic coherence, with a frequency of 27 cm-1 and coupled to the B880 electronic transition, may contribute to the B800 → B880 EET process.

Heterospecific pollen avoidance strategy prevails in the generalized plant-pollinator network on Yongxing Island.

Heterospecific pollen (HP) deposition varies widely among species in communities, which has been explicated by two adaptation strategies: HP avoidance and HP tolerance. Studies of the plant-pollinator network have uncovered that oceanic island communities are highly generalized and strongly connected. It remains unclear, however, which strategy prevails in such communities. We examined stigma pollen deposition on 29 plant species, and assessed patterns of HP load size and diversity in the Yongxing Island community. We assessed the effects of phenotypic specialization and species-level network structural properties of plant species on pollen deposition among species. The hypothesis of three accrual patterns of HP within species was tested by illustrating the relationship between conspecific pollen (CP) and HP receipt. Extensive variation occurred among species in HP receipt, while 75.9% of species received less than 10% HP and one species received more than 40% HP throughout the community. Flower size strongly drives the variation of HP receipt, while network structural properties had no effect on the pollen receipt. Nineteen species showed no relationship between the number of HP and CP loads, and they received smaller HP load sizes and lower HP proportions. Most plant species evolved HP avoidance strategy, and HP receipt was an occasional event for most plant species in the generalized community. HP and CP receipts are independent of each other in plant species with the HP avoidance mechanism. Our results highlight that plants in the generalized pollination system may preferentially select to minimize the HP load on stigmas.

Structural insights into the unusual core photocomplex from a triply extremophilic purple bacterium, Halorhodospira halochloris.

Halorhodospira (Hlr.) halochloris is a triply extremophilic phototrophic purple sulfur bacterium, as it is thermophilic, alkaliphilic, and extremely halophilic. The light-harvesting-reaction center (LH1-RC) core complex of this bacterium displays an LH1-Qy transition at 1,016 nm, which is the lowest-energy wavelength absorption among all known phototrophs. Here we report the cryo-EM structure of the LH1-RC at 2.42 Å resolution. The LH1 complex forms a tricyclic ring structure composed of 16 αßγ-polypeptides and one αß-heterodimer around the RC. From the cryo-EM density map, two previously unrecognized integral membrane proteins, referred to as protein G and protein Q, were identified. Both of these proteins are single transmembrane-spanning helices located between the LH1 ring and the RC L-subunit and are absent from the LH1-RC complexes of all other purple bacteria of which the structures have been determined so far. Besides bacteriochlorophyll b molecules (B1020) located on the periplasmic side of the Hlr. halochloris membrane, there are also two arrays of bacteriochlorophyll b molecules (B800 and B820) located on the cytoplasmic side. Only a single copy of a carotenoid (lycopene) was resolved in the Hlr. halochloris LH1-α3ß3 and this was positioned within the complex. The potential quinone channel should be the space between the LH1-α3ß3 that accommodates the single lycopene but does not contain a γ-polypeptide, B800 and B820. Our results provide a structural explanation for the unusual Qy red shift and carotenoid absorption in the Hlr. halochloris spectrum and reveal new insights into photosynthetic mechanisms employed by a species that thrives under the harshest conditions of any phototrophic microorganism known.

Patient-related factors related to prolonged preparation-to-colonoscopy interval and insufficient purgative intake before colonoscopy: A post-hoc observational study.

OBJECTIVES: Prolonged preparation-to-colonoscopy (PC) interval and insufficient purgative intake (PI) are two important indicators for quality of bowel preparation for colonoscopy. We aimed to investigate patient-related factors associated with increased PC interval or insufficient PI. METHODS: The post-hoc regression analyses were performed using the data from two prospective studies (NCT04434625 and NCT04101097). Patients receiving reinforced instructions for bowel preparation were recruited. The co-primary outcomes included prolonged PC interval or insufficient PI. RESULTS: Altogether 1806 patients from five endoscopic centers underwent bowel preparation from September 2019 to March 2021. The cut-off values were 6 h for PC interval and 80% for PI. In all, 116 (6.4%) and 73 (4.0%) presented an extended PC interval and insufficient PI, respectively. Multivariate logistic regression analysis showed that a low education level was significantly associated with PC interval ≥6 h. Female sex, body mass index (BMI), and coronary artery disease (CAD) were found to be significantly correlated with insufficient PI in univariate analysis, while multivariate analysis demonstrated BMI <20 kg/m2 (odds ratio [OR] 4.14, 95% confidence interval [CI] 1.92-8.94, P < 0.001) and 20-25 kg/m2 (OR 2.23, 95% CI 1.33-3.73, P = 0.002) and CAD (OR 3.23, 95% CI 1.22-8.53, P = 0.018) were identified as independent risk factors for PI <80%. CONCLUSIONS: In spite of reinforced education, a number of patients did not follow the instructions for bowel preparation. The factors for a prolonged PC interval did not overlap with those for insufficient PI. Individualized interference may be considered in different subpopulations.

The Protective Role of Non-Photochemical Quenching in PSII Photo-Susceptibility: A Case Study in the Field.

Non-photochemical quenching (NPQ) has been regarded as a safety valve to dissipate excess absorbed light energy not used for photochemistry. However, there exists no general consensus on the photoprotective role of NPQ. In the present study, we quantified the Photosystem II (PSII) photo-susceptibilities (mpi) in the presence of lincomycin, under red light given to five shade-acclimated tree species grown in the field. Photosynthetic energy partitioning theory was applied to investigate the relationships between mpi and each of the regulatory light-induced NPQ [Y(NPQ)], the quantum yield of the constitutive nonregulatory NPQ [Y(NO)] and the PSII photochemical yield in the light-adapted state [Y(PSII)] under different red irradiances. It was found that in the low to moderate irradiance range (50-800 µmol m-2 s-1) when the fraction of open reaction centers (qP) exceeded 0.4, mpi exhibited no association with Y(NPQ), Y(NO) and Y(PSII) across species. However, when qP < 0.4 (1,500 µmol m-2 s-1), there existed positive relationships between mpi and Y(NPQ) or Y(NO) but a negative relationship between mpi and Y(PSII). It is postulated that both Y(NPQ) and Y(NO) contain protective and damage components and that using only Y(NPQ) or Y(NO) metrics to identify the photo-susceptibility of a species is a risk. It seems that qP regulates the balance of the two components for each of Y(NPQ) and Y(NO). Under strong irradiance, when both protective Y(NPQ) and Y(NO) are saturated/depressed, the forward electron flow [i.e. Y(PSII)] acts as the last defense to resist photoinhibition.

[Characteristics and influencing factors of soil nitrification potential in coastal salinized farmland]. / æ»¨æµ·ç›æ¸å†œç”°åœŸå£¤ç¡åŒ–åŠ¿ç‰¹å¾åŠå ¶å½±å“å› ç´ .

Understanding the nitrification capacity of coastal saline farmland soils and its main drivers is of great significance to regulate soil nitrification and improve the utilization efficiency of nitrogen fertilization in farmland. Using a combination of field investigations and laboratory analyses, we examined farmland soil nitrification potential and soil physical, chemical, and biological properties in the coastal muddy tidal flat saline soil area (Dongying and Dongtai). We established the correlation between soil properties and soil nitrification potential with multiple stepwise regression analyses and structural equation modeling (SEM). The results showed that soil pH value was relatively stable and other soil properties and soil nitrification potential varied in coastal saline farmland. The soil nitrification potential ranged from 0.04 to 10.42 mg·kg-1·d-1 and decreased with the increases of soil salinization level. Soil nitrification potential had the strongest correlation with soil organic matter, cation exchange capacity, and Cl-, with the correlation coefficient being 0.409, 0.397 and -0.337, respectively. The results of multiple stepwise regression analysis showed that Na+, silt, cation exchange capacity, and CO32-+HCO3- were the main influencing factors of soil nitrification potential. The results from the SEM analysis suggested that Na+, silt, cation exchange capacity, and CO32-+HCO3- directly affected soil nitrification potential, and soil organic matter, clay, Cl- and SO42- had indirect effects. In all, soil Na+ and cation exchange capacity were the two main factors affecting nitrification. Adjusting soil NaCl content and cation exchange capacity was an effective means of regulating soil nitrification.

Biochar Addition Inhibits Nitrification by Shifting Community Structure of Ammonia-Oxidizing Microorganisms in Salt-Affected Irrigation-Silting Soil.

Biochar has been widely recognized as an effective and eco-friendly ameliorant for saline soils, but information about the mechanism of how biochar influences nitrification in salt-affected agroecosystem remains fragmented. An incubation experiment was performed on the salt-affected soil collected from a three-consecutive-year experiment at biochar application gradients of 7.5 t⋅ha-1, 15 t⋅ha-1 and 30⋅t ha-1 and under nitrogen (N) fertilization. Responses of the nitrification rate (NR), numbers of ammonia monooxygenase (amoA) gene copies, and community structures of ammonia-oxidizing bacteria (AOB) and archaea (AOA) to biochar application were investigated. The results indicated that, under N fertilization, the NR and numbers of amoA-AOB and amoA-AOA gene copies negatively responded to biochar addition. Biochar application increased the community diversity of AOB but decreased that of AOA. Biochar addition and N fertilization shifted the AOB community from Nitrosospira-dominated to Nitrosospira and Nitrosomonas-dominated, and altered the AOA community from Nitrososphaera-dominated to Nitrososphaera and Nitrosopumilus-dominated. The relative abundance of Nitrosospira, Nitrosomonas and Nitrosopumilus decreased, and that of Nitrosovibrio and Nitrososphaera increased with biochar application rate. Soil SOC, pH and NO3--N explained 87.1% of the variation in the AOB community, and 78.1% of the variation in the AOA community was explanatory by soil pH and SOC. The SOC and NO3--N influenced NR through Nitrosovibrio, Nitrosomonas, Norank_c_environmental_samples_p_Crenarchaeota and amoA-AOB and amoA-AOA gene abundance. Therefore, biochar addition inhibited nitrification in salt-affected irrigation-silting soil by shifting the community structures of AOB and AOA and reducing the relative abundance of dominant functional ammonia-oxidizers, such as Nitrosospira, Nitrosomonas and Nitrosopumilus.

Effects of Delayed Mating on the Reproductive Performance of Henosepilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae).

Henosepilachna vigintioctopunctata (F.) is a serious pest of numerous solanaceous crops in many Asian countries. The purpose of this study was to clarify the effects of delayed mating on mating success, fecundity, fertility, pre-oviposition period, oviposition period, adult longevity, and population life table parameters (including net reproductive rate, intrinsic and finite rates of increase, doubling time, and mean generation time) of H. vigintioctopunctata. Beginning three days after emergence for both sexes, mating was delayed an additional 0, 2, 4, 6, or 8 days. We compared the data when mating was delayed for males only with the data when mating was similarly delayed for females only. Reproductive and life table parameters were calculated from the two data sets and compared. The results showed that the preoviposition and oviposition period of adults was significantly reduced by delayed mating, while the preoviposition period was not significantly different in adults mated at older ages. The mating success rate, fecundity, and proportion of hatching eggs decreased with increasing mating age. Longevity was not affected by the age at mating. Mating delay also affected the life table parameters of H. vigintioctopunctata, with a similar trend observed in the net reproductive rate and intrinsic and finite rates of increase, all of which decreased gradually as the number of delay days increased. The population doubling time increased with increases in mating age. The results also showed that delayed mating was an effective measure to consider in controlling H. vigintioctopunctata. It is hoped that our data will provide a scientific basis and contribute technical guidance for forecasting and integrated management of this pest.

Electrostatic charge controls the lowest LH1 Qy transition energy in the triply extremophilic purple phototrophic bacterium, Halorhodospira halochloris.

Halorhodospira (Hlr.) halochloris is a unique phototrophic purple bacterium because it is a triple extremophile-the organism is thermophilic, alkalophilic, and halophilic. The most striking photosynthetic feature of Hlr. halochloris is that the bacteriochlorophyll (BChl) b-containing core light-harvesting (LH1) complex surrounding its reaction center (RC) exhibits its LH1 Qy absorption maximum at 1016 nm, which is the lowest transition energy among phototrophic organisms. Here we report that this extraordinarily red-shifted LH1 Qy band of Hlr. halochloris exhibits interconvertible spectral shifts depending on the electrostatic charge distribution around the BChl b molecules. The 1016 nm band of the Hlr. halochloris LH1-RC complex was blue-shifted to 958 nm upon desalting or pH decrease but returned to its original position when supplemented with salts or pH increase. Resonance Raman analysis demonstrated that these interconvertible spectral shifts are not associated with the strength of hydrogen-bonding interactions between BChl b and LH1 polypeptides. Furthermore, circular dichroism signals for the LH1 Qy transition of Hlr. halochloris appeared with a positive sign (as in BChl b-containing Blastochloris species) and opposite those of BChl a-containing purple bacteria, possibly due to a combined effect of slight differences in the transition dipole moments between BChl a and BChl b and in the interactions between adjacent BChls in their assembled state. Based on these findings and LH1 amino acid sequences, it is proposed that Hlr. halochloris evolved its unique and tunable light-harvesting system with electrostatic charges in order to carry out photosynthesis and thrive in its punishing hypersaline and alkaline habitat.

[Influencing mechanism of soil salinization on nitrogen transformation processes and efficiency improving methods for high efficient utilization of nitrogen in salinized farmland]. / ç›æ¸åŒ–å¯¹å†œç”°æ°®ç´ è½¬åŒ–è¿‡ç¨‹çš„å½±å“æœºåˆ¶å’Œå¢žæ•ˆè°ƒæŽ§é€”å¾„.

Based upon the review of the status of nitrogen use efficiency in salinized farmland in China, we summarized the effect of salinization on key processes of nitrogen transformation in farmland soil, analyzed the microbial mechanism underlying nitrogen transformation, and summed up the main ways for high efficient utilization of nitrogen in salinized farmland. Salinization had thre-shold effects on mineralization, nitrification, and denitrification of nitrogen from farmland soil, with the influence varying greatly in different scopes. Salinity and secondary barriers had different effects on microorganisms, with threshold in their effects. The most widely used methods for nitrogen synergism regulation in salinized farmland include soil conditioner, biomass material, growing salt-tole-rant plants, optimizing the ratio of different nitrogen forms, and biological inhibitor. We proposed current research shortcomings and future research directions of nitrogen cycle processes in salinized farmland. This study was of great significance for reducing nitrogen loss, enhancing utilization of nutrient from fertilizers, and controlling agricultural non-point source pollution in salinized farmland.

Biochar and fulvic acid amendments mitigate negative effects of coastal saline soil and improve crop yields in a three year field trial.

China with large area of land planted with crops are suffering secondary salinization in coastal area for the lack of fresh water and saltwater intrusion to the groundwater. The purpose of this study was to investigate the effects of biochar (BC) and fulvic acid (FA) on the amelioration of coastal saline soil and their impact on crop yields under maize-barley rotation system. A three year field experiment was conducted in a saline soil on a farm in coastal area of east Jiangsu Province, China. A maize-barley rotation system had been carried out for ten years with local conventional management before the experiment. The saline soil was amended with BC at rates of 0, 7.5 t ha-1 (BC1), 15 t ha-1 (BC2) and 30 t ha-1 (BC3) alone or combined with fulvic acid (1.5 t ha-1) compared with control. Fertilizers were applied under normal planting strategies. The BC was added only once during the four growing seasons, and the FA was applied before each sowing. Soil salinity changed significantly during the three year field experiment. This was mainly due to the great quantity of rain during the period of maize cultivation. Although Na+, Cl- and SO42- in BC and /or FA treatments significantly decreased, the pH value increased up to 9.0 as the CO32- + HCO3-content increased. Total organic carbon (TOC) and phosphorus (TP) responded positively to biochar addition rate. BC applied with appropriate rate at 15 t ha-1 (BC2) in combination with FA showed optimal effects on soil salinity amelioration, soil physics properties regulation, soil nutrition improvement and crop yields increase. The TOC and TP was 5.2 g kg-1 and 507 mg kg-1 in BC2 + FA treatment, which were lower than BC3 and BC3 + FA treatments. However, the highest total grain yield was obtained in the BC2 + FA treatment, and the total yield was increased by 62.9% over the CK. This study emphasizes that using combined organic amendment of BC with FA for profitable and sustainable use of salt-affected soils would be practicable.

Nectar supplementation changes pollinator behaviour and pollination mode in Pedicularis dichotoma: implications for evolutionary transitions.

Backgrounds and Aims: Gain or loss of floral nectar, an innovation in floral traits, has occurred in diverse lineages of flowering plants, but the causes of reverse transitions (gain of nectar) remain unclear. Phylogenetic studies show multiple gains and losses of floral nectar in the species-rich genus Pedicularis. Here we explore how experimental addition of nectar to a supposedly nectarless species, P. dichotoma, influences pollinator foraging behaviour. Methods: The liquid (nectar) at the base of the corolla tube in P. dichotoma was investigated during anthesis. Sugar components were measured by high-performance liquid chromatography. To understand evolutionary transitions of nectar, artificial nectar was added to corolla tubes and the reactions of bumble-bee pollinators to extra nectar were examined. Key Results: A quarter of unmanipulated P. dichotoma plants contained measurable nectar, with 0.01-0.49 µL per flower and sugar concentrations ranging from 4 to 39 %. The liquid surrounding the ovaries in the corolla tubes was sucrose-dominant nectar, as in two sympatric nectariferous Pedicularis species. Bumble-bees collected only pollen from control (unmanipulated) flowers of P. dichotoma, adopting a sternotribic pollination mode, but switched to foraging for nectar in manipulated (nectar-supplemented) flowers, adopting a nototribic pollination mode as in nectariferous species. This altered foraging behaviour did not place pollen on the ventral side of the bees, and sternotribic pollination also decreased. Conclusion: Our study is the first to quantify variation in nectar production in a supposedly 'nectarless' Pedicularis species. Flower manipulations by adding nectar suggested that gain (or loss) of nectar would quickly result in an adaptive behavioural shift in the pollinator, producing a new location for pollen deposition and stigma contact without a shift to other pollinators. Frequent gains of nectar in Pedicularis species would be beneficial by enhancing pollinator attraction in unpredictable pollination environments.

Effect of Dietary Protein and Carbohydrates on Survival and Growth in Larvae of the Henosepilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae).

The ratio of protein and carbohydrate in an insect's nutritional regime can significantly influence its survival, growth, and fecundity. The effects of 11 different artificial diets containing protein (p): carbohydrate (c) ratios were determined in larvae of the phytophagus ladybug, Henosepilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae). We recorded the developmental times and survival rates of the larvae and weighed their pupae. When the concentration of carbohydrates was kept constant while the concentration of proteins was increased (p29:c20, p31:c20, p33:c20, and p35:c20), H. vigintioctopunctata could successfully complete the larval and pupal stages. The highest survival rate and greatest pupal mass of H. vigintioctopunctata were 72% and 19.5 mg, respectively, when reared on the p33:c20 diet. H. vigintioctopunctata larvae, however, were unable to develop into adults when the concentration of protein remained constant while the level of carbohydrates was increased (p20:c23, p20:c25, p20:c27, and p20:c29), or when the total amount (p + c) was kept at 48% (p22:c26, p 24:c24, p26:c22). Evidently, changing the availability of quality diet, especially the total protein levels, can significantly affect the performance to H. vigintioctopunctata. Our results indicated that the maximum development and survival of H. vigintioctopunctata larvae occurred within a narrow range-when the p:c ratio was (33:20).

Bt cotton producing Cry1Ac and Cry2Ab does not harm two parasitoids, Cotesia marginiventris and Copidosoma floridanum.

Cabbage looper, Trichoplusia ni (Hübner) is an important lepidopteran pest on many vegetable and greenhouse crops, and some field crops. Although there are no commercial transgenic Bt vegetable or greenhouse crops, T. ni is a target of Bollgard II cotton, which produces Cry1Ac and Cry2Ab. We expand on previous work that examined the effect of Bt crops on parasitoids using Bt-resistant lepidopteran populations as hosts. Cry1Ac/Cry2Ab-resistant T. ni larvae were used to eliminate host quality effects and to evaluate the direct effects of Bt cotton on the parasitoids Copidosoma floridanum (Ashmead) and Cotesia marginiventris (Cresson). These tri-trophic studies confirm that Bt cotton had no significant impact on development, success of parasitism, survival and adult longevity of C. marginiventris when using Bt-resistant T. ni fed on Bt cotton. Similarly, this Bt cotton had no significant impact on the development, mummy weight and the number of progeny produced by C. floridanum. Our studies verified that lyophilized Bt crop tissue maintained its insecticidal bioactivity when incorporated into an artificial diet, demonstrating that hosts and parasitoids were exposed to active Cry proteins. The egg-larval parasitoid C. floridanum, or similar species that consume their entire host, should be considered useful surrogates in risk assessment of Bt crops to non-target arthropods.

Demographic Comparison of Henosepilachna vigintioctopunctata (F.) (Coleoptera: Coccinellidae) Reared on Three Cultivars of Solanum melongena L. and a Wild Hostplant Solanum nigrum L.

Henosepilachna vigintioctopunctata (F.) is a widespread pest found on many solanaceous vegetables. The development and fecundity of H. vigintioctopunctata were studied on three cultivars ('Zihong', 'Eyou', and 'Baijiao') of eggplant, Solanum melongena L., using the two-sex life table theory. These results were then compared with similar parameters from a wild alternate host, Solanum nigrum. Our results showed that there were no significant differences between the developmental times of the larval stages, pupae, oviposition period, adult longevity, and the fecundity of H. vigintioctopunctata reared on the three eggplant cultivars. The survival rates of H. vigintioctopunctata larvae reared on the three eggplant cultivars were higher than that on S. nigrum. The fecundity of H. vigintioctopunctata adults reared on S. nigrum (724.12 eggs), however, was significantly higher than on each of the three eggplant cultivars. The values for the intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R0) for H. vigintioctopunctata when reared on S. nigrum were 0.1225 d-1,1.1303 d-1, and 299.6 offspring, respectively. Each of these was significantly higher than comparable values when reared on the cultivar Eyou and Baijiao but were not different from those reared on the Zihong. Our results indicated that H. vigintioctopunctata is well adapted to all tested host plant cultivars and that S. nigrum is an important alternate wild hostplant that may potentially contribute to future outbreaks of H. vigintioctopunctata if not taken into consideration when planning an integrated control strategy against the pest.

Pollen size strongly correlates with stigma depth among Pedicularis species.

Darwin proposed that pollen size should be positively correlated with stigma depth rather than style length among species given that pollen tubes first enter the stigma autotrophically, then grow through the style heterotrophically. However, studies often show a positive relationship between pollen size and style length. Five floral traits were observed to be correlated among 42 bumblebee-pollinated Pedicularis species (Orobanchaceae) in which stigmas are distinct from styles. The phylogenetic independent contrast analysis revealed that pollen grain volume was more strongly correlated with stigma depth than with style length, consistent with Darwin's functional hypothesis between pollen size and stigma depth.

Are long corolla tubes in Pedicularis driven by pollinator selection?

The evolution of long corolla tubes has been hypothesized to be driven by long-tongued pollinators. Corolla tubes in Pedicularis species can be longer than 10 cm which may function as flower stalks to increase visual attractiveness to pollinators because these species provide no nectar and are pollinated by bumblebees. The corolla tube length was manipulated (shorter or longer) in two Pedicularis species in field to examine whether longer tubes are more attractive to pollinators and produce more seeds than short tubes. Our results did not support the pollinator attraction hypothesis, leaving the evolution of long tubes in Pedicularis remains mysterious.

Using resistant prey demonstrates that Bt plants producing Cry1Ac, Cry2Ab, and Cry1F have no negative effects on Geocoris punctipes and Orius insidiosus.

Geocoris punctipes (Say) and Orius insidiosus (Say) are generalist predators found in a wide range of crops, including cotton (Gossypium hirsutum L.) and maize (Zea mays L.), where they provide important biological control services by feeding on an array of pests, including eggs and small larvae of caterpillars. A high percentage of cotton and maize in the United States and several other countries are transgenic cultivars that produce one or more of the insecticidal Cry proteins of Bacillus thuringiensis Berliner (Bt). Here we quantify effects of three Cry proteins on the life history of these predators over two generations when they are exposed to these Cry proteins indirectly through their prey. To eliminate the confounding prey quality effects that can be introduced by Bt-susceptible prey, we used Cry1Ac/Cry2Ab-resistant Trichoplusia ni (Hübner) and Cry1 F-resistant Spodoptera frugiperda (J.E. Smith) in a series of tri-trophic studies. Survival, development, adult mass, fecundity, and fertility were similar when predators consumed larvae feeding on Cry1Ac/Cry2Ab cotton or Cry1 F maize compared with prey feeding on isogenic or near-isogenic cotton or maize. Repeated exposure of the same initial cohort over a second generation also resulted in no differences in life-history traits when feeding on non-Bt- or Bt-fed prey. Enzyme-linked immunosorbent assay showed that predators were exposed to Bt Cry proteins from their prey and that these proteins became increasingly diluted as they moved up the food chain. Results show a clear lack of effect of three common and widespread Cry proteins on these two important predator species. The use of resistant insects to eliminate prey quality effects provides a robust and meaningful assessment of exposure and hazard.

Eliminating host-mediated effects demonstrates Bt maize producing Cry1F has no adverse effects on the parasitoid Cotesia marginiventris.

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an important pest of maize in the United States and many tropical areas in the western hemisphere. In 2001, Herculex I(®) (Cry1F) maize was commercially planted in the United States to control Lepidoptera, including S. frugiperda. In 2006, a population of S. frugiperda was discovered in Puerto Rico that had evolved resistance to Cry1F maize in the field, making it the first well-documented case of an insect with field resistance to a plant producing protein from Bacillus thuringiensis (Bt). Using this resistant population, we conducted tri-trophic studies with a natural enemy of S. frugiperda. By using resistant S. frugiperda, we were able to overcome possible prey-mediated effects and avoid concerns about potential differences in laboratory- or field-derived Bt resistance. We used the Cry1F-resistant S. frugiperda to evaluate effects of Cry1F on Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae), a larval endoparasitoid of S. frugiperda, over five generations. Our results clearly demonstrate that Cry1F maize does not affect development, parasitism, survivorship, sex ratio, longevity or fecundity of C. marginiventris when they parasitize Cry1F maize-fed S. frugiperda. Furthermore, the level of Cry1F protein in the leaves was strongly diluted when transferred from Bt maize to S. frugiperda and was not detected in larvae, cocoons or adults of C. marginiventris. Our results refute previous reports of C. marginiventris being harmed by Bt proteins and suggest that such results were caused by prey-mediated effects due to using Bt-susceptible lepidopteran hosts.

Bt crops producing Cry1Ac, Cry2Ab and Cry1F do not harm the green lacewing, Chrysoperla rufilabris.

The biological control function provided by natural enemies is regarded as a protection goal that should not be harmed by the application of any new pest management tool. Plants producing Cry proteins from the bacterium, Bacillus thuringiensis (Bt), have become a major tactic for controlling pest Lepidoptera on cotton and maize and risk assessment studies are needed to ensure they do not harm important natural enemies. However, using Cry protein susceptible hosts as prey often compromises such studies. To avoid this problem we utilized pest Lepidoptera, cabbage looper (Trichoplusia ni) and fall armyworm (Spodoptera frugiperda), that were resistant to Cry1Ac produced in Bt broccoli (T. ni), Cry1Ac/Cry2Ab produced in Bt cotton (T. ni), and Cry1F produced in Bt maize (S. frugiperda). Larvae of these species were fed Bt plants or non-Bt plants and then exposed to predaceous larvae of the green lacewing Chrysoperla rufilabris. Fitness parameters (larval survival, development time, fecundity and egg hatch) of C. rufilabris were assessed over two generations. There were no differences in any of the fitness parameters regardless if C. rufilabris consumed prey (T. ni or S. frugiperda) that had consumed Bt or non-Bt plants. Additional studies confirmed that the prey contained bioactive Cry proteins when they were consumed by the predator. These studies confirm that Cry1Ac, Cry2Ab and Cry1F do not pose a hazard to the important predator C. rufilabris. This study also demonstrates the power of using resistant hosts when assessing the risk of genetically modified plants on non-target organisms.