The evolution of insect metallothioneins.

Metallothioneins (MTs) are a family of cysteine-rich metal-binding proteins that are important in the chelating and detoxification of toxic heavy metals. Until now, the short length and the low sequence complexity of MTs have hindered the inference of robust phylogenies, hampering the study of their evolution. To address this longstanding question, we applied an iterative BLAST search pipeline that allowed us to build a unique dataset of more than 300 MT sequences in insects. By combining phylogenetics and synteny analysis, we reconstructed the evolutionary history of MTs in insects. We show that the MT content in insects has been shaped by lineage-specific tandem duplications from a single ancestral MT. Strikingly, we also uncovered a sixth MT, MtnF, in the model organism Drosophila melanogaster. MtnF evolves faster than other MTs and is characterized by a non-canonical length and higher cysteine content. Our methodological framework not only paves the way for future studies on heavy metal detoxification but can also allow us to identify other previously unidentified genes and other low complexity genomic features.

Mating Disruption of Chilo suppressalis From Sex Pheromone of Another Pyralid Rice Pest Cnaphalocrocis medinalis (Lepidoptera: Pyralidae).

The rice stem borer, Chilo suppressalis (Walker), and the rice leaf folder, Cnaphalocrocis medinalis Guenée, are two of the most destructive lepidopteran pests in rice. Since these two pyralid insects overlap in their occurrence in rice paddy fields, farmers prefer to set their pheromone-baited traps together in the rice fields for their monitoring. However, our field observation demonstrated that no male adult of C. suppressalis was captured in traps baited with commercial sex pheromone of C. suppressalis (CCS) combined with commercial sex pheromone of C. medinalis (CCM). To confirm that the C. medinalis sex pheromone component(s) interfere with the attraction of males of the rice stem borers to their conspecific females, single components of C. medinalis sex pheromone combined with CCS in traps were tested in the laboratory and rice paddy field. The results revealed that the two alcohol components in CCM, i.e., (Z)-11-octadecen-1-ol (Z11-18: OH) and (Z)-13-octadecen-1-ol (Z13-18: OH) may cause a significant reduction in capturing C. suppressalis males caused by CCS. We recommend against using these sex pheromones together in the field and suggest that Z11-18: OH and Z13-18: OH could be potential inhibitors or antagonists of C. suppressalis sex pheromone to control the rice stem borer.

Identification and Gene Expression Analysis of the Pheromone Biosynthesis Activating Neuropeptide Receptor (PBANR) From the Ostrinia furnacalis (Lepidoptera: Pyralidae).

Pheromonal communication is important in insect mate finding and reproduction. Identifying components of pest insect pheromone system is a first step to disrupt pest insect reproduction. In this study, we identified and cloned the pheromone biosynthesis activating neuropeptide receptor (PBANR) from the Asian corn borer, Ostrinia furnacalis (Guenée) (Lepidoptera: Pyralidae), which is one of the most damaging pests of corn and other crops in parts of Asia and Australia. The O. furnacalis PBANR (OstfuPBANR) gene has an ORF of 1,086 bp and encoded 362 amino acids with seven transmembrane domains and had a high sequence identity to known lepidopteran PBANRs. Expression analysis showed that OstfuPBANR was highly expressed in the pheromone glands compared with other tissues, consistent with other studies. Interestingly, OstfuPBANR was expressed higher in the larval stages compared to the pupal or adult stages, suggesting that OstfuPBANR may have broad functions in larva beyond adult pheromone synthesis.

HPLC Separation of 2-Ethyl-5(6)-methylpyrazine and Its Electroantennogram and Alarm Activities on Fire Ants (Solenopsis invicta Buren).

2-Ethyl-3,6-dimethylpyrazine (EDMP) was an alarm pheromone component isolated from the mandibular gland of the red imported fire ant, Solenopsis invicta Buren. Several pyrazine analogues have been previously found to elicit significant alarm responses in S. invicta workers. This study aimed to separate the commercially available 2-ethyl-5(6)-methylpyrazine (EMP), i.e., a mixture of 2-ethyl-6-methylpyrazine (2E6MP) and 2-ethyl-5-methylpyrazine (2E5MP), and to examine both electroantennogram (EAG) and behavioral responses of S. invicta workers to EMP and the purified isomers. HPLC separations were achieved using a polysaccharide chiral stationary phase (Chiralpak AD-H) column with both mobile phases: Cyclohexane/isopropanol, and hexane/isopropanol. A ratio of 99:1 was selected for the separation of EMP at semipreparative level. The structures of the isomers obtained through the cyclohexane/isopropanol mobile phase were confirmed by detailed analyses of 2D-HSQC- and -HMBC-NMR data. The two isomers showed differential methine C⁻H correlations evidenced by 2D-HMBC-NMR spectra. The two concentrated fractions obtained through hexane/isopropanol mobile phase were subjected to EAG test and behavioral bioassay on S. invicta workers. The two HPLC−purified isomers, 2E6MP and 2E5MP, and their mixture (1:1) at same dose elicited similar EAG and alarm responses, indicating that these two isomers are equally active. The 2D-NMR−spectroscopic characterization, and electrophysiological and alarm activities of 2E6MP and 2E5MP were reported here for the first time.

Bioaccumulation of Cadmium Affects Development, Mating Behavior, and Fecundity in the Asian Corn Borer, Ostrinia furnacalis.

Heavy metal pollution is becoming an increasingly serious problem in agricultural ecosystems. Heavy metals such as cadmium (Cd) accumulate in the food chain and may lead to detrimental effects on the physiological functions of living organisms, including herbivorous insects. One such example is the Asian Corn Borer, Ostrinia furnacalis (Lepidoptera: Pyralidae). However, how Cd can affect the development and reproduction of O. furnacalis is largely unknown. In this study, we exposed larvae of O. furnacalis to a diet containing Cd and investigated the effects of Cd on the development, mating behavior, and fecundity of the insect. We showed that Cd accumulates in the larvae and inhibits development by extending larval and pupal duration and decreasing the survival rate. The excretion of Cd through multiple routes during the larval and pupal stages resulted in low levels of residual Cd in the adult insects, which were not fed with Cd. However, the mating behavior and fecundity of these insects were significantly affected, compared to control insects. This suggests that the bioaccumulation of heavy metals such as Cd has long lasting and detrimental effects on O. furnacalis over the entire life cycle, affecting fecundity, even when specimens are only exposed at an early life stage.

Molecular characters and expression analysis of the gene encoding eclosion hormone from the Asian corn borer, Ostrinia furnacalis.

Using rapid amplification of cDNA ends (RACE), the cDNA encoding eclosion hormone (EH) was cloned from the brain of Ostrinia furnacalis. The full Osf-EH cDNA is 986 bp and contains a 267 bp open reading frame encoding an 88 amino acid preprohormone, which including a hydrophobic 26 amino acid signal peptide and a 62 amino acid mature peptide. The mature Osf-EH shows high identity with Manduca sexta (95.2%), Helicoverpa armigera (91.9%) and Bombyx mori (85.5%), but low identify with Tribolium castaneum (63.6%), Drosophila melanogaster (56.5%) and Apis mellifera (54.8%). Using the HMMSTR Prediction Server, the 3D structure of Osf-EH was modeled. There are four beta-turns and three alpha-helixes predicted in Osf-EH, with the pattern of beta-beta-alpha-alpha-beta-beta-alpha. Northern blot analysis indicated a 1.0 kb transcript present only in the brain. The Osf-EH mRNA can not be detected in other neural tissues, such as the suboesophageal ganglion, thoracic ganglion, abdominal ganglion and other non-neural tissues, such as the midgut, fat body and epidermis. The Osf-EH mRNA content in the brain was measured using the combined method of quantitative RT-PCR and Southern blotting, which reached its highest level the day before the molt.

[Effects of conservation tillage on soil water condition and winter wheat yield in farmland]. / 保护性耕作对农田土壤水分和冬小麦产量的影响.

Conservation tillage is one of the most important agricultural management measures on soil water conservation and crop yield increments. Based on long-term experiment during 2011 to 2016, effects of different tillage treatments, including conventional tillage, no-tillage and subsoiling treatments, on soil water condition, crop yield and water use efficiency were analyzed. The results showed that the average and relative soil water conservation rate was 7.3% and -0.68% at jointing stage of winter wheat under no tillage and subsoiling treatments, respectively. Compared with conventional tillage, soil water storage significantly increased in 0-60 cm soil layer at jointing stage of winter wheat under no-tillage. Besides, the mean values of soil water content significantly increased in 0-100 cm soil layer at jointing, flowering, filling, and harvesting stages under no tillage treatment while that was not significantly increased at jointing stage under subsoiling treatment. Furthmore, no-tillage treatment significantly increased the yield and water use efficiency of winter wheat, especially in the dry years. Therefore, soil moisture conservation ability and yield increment of no tillage was better than that of the subsoiling treatment in dry years.

EAG and behavioral responses of Helicoverpa armigera males to volatiles from poplar leaves and their combinations with sex pheromone.

Electroantennogram (EAG) evaluation of selected compounds from wilted leaves of black poplar, Populus nigra, showed that phenyl acetaldehyde, methyl salicylate, (E)-2-hexenal elicited strong responses from male antennae of Helicoverpa armigera. When mixed with sex pheromone (Ph), some volatiles, e.g. phenyl acetaldehyde, benzyl alcohol, phenylethanol, methylsalicylate, linalool, benzaldehyde, (Z)-3-hexenol, (Z)-3-hexenylacetate, (Z)-6-nonenol, cineole, (E)-2-hexenal, and geraniol elicited stronger responses from male antennae than Ph alone. Wind tunnel bioassay demonstrated that various volatiles could either enhance or inhibit the effect of synthetic sex pheromone. (E)-2-hexenal, (Z)-3-hexenol and linalool in combination with Ph could not induce any male to land on source at all, whereas phenyl acetaldehyde, benzaldehyde, (Z)-6-nonenol and salicylaldehyde combined with Ph enhanced male response rates by 58.63%, 50.33%, 51.85% and 127.78%, respectively, compared to Ph alone. These results suggested that some volatiles should modify sex pheromone caused behavior and that some of them could possibly be used as a tool for disrupting mating or for enhancing the effect of synthetic sex pheromone in the field.

[Circadian rhythm of emergence and reproduction of Micromelalopha troglodyta (Lepidoptera: Notodontidae)].

Micromelalopha troglodyta (Graeser) is one of serious defoliators of poplars. In order to explore the occurrence regularity of emergence and reproductive behavior of M. troglodyte, which could provide references to the application of ecological control techniques, the circadian rhythms of emergence, calling, mating and oviposition were studied at (27 ± 1) degrees C and (60 ± 10)% RH under a 14L:10D photoperiod. The results showed that the emergence peak of the female occurred at the 7th day of the pupal stage, while the male at 8th day. As for the circadian rhythm during 24 hours, most individuals of both sexes emerged from the 6th hour of the photophase to the 2th hour of the scotophase. The 11th hour after initiation of the photophase was the emergence peak of female, while that of the male was 1 hour later. Female M. troglodyte after emergence did not call until the scotophase. The calling percentage reached the peak at the 6th-7th hour of the scotophase which increased with age of 1-3 days and reached 69.8% at the 3rd day, and then went down gradually. In the cage of only a pair of female and male, adults started mating after the 5th hour of the scotophase, and reached peak at the 7th-8th hour. But in the cage of multiple pairs of adult moths, they started mating after 0.5 hour of the scotophase, and the peak was 1.5 hours later than one pair's. Eggs laid by females at the age of 1 to 3 days accounted for 68.4% of their total lifetime fecundity, and then the oviposition gradually reduced with the age.

Quantitative analysis of alkaloidal constituents in imported fire ants by gas chromatography.

A method based on silica gel chromatography and GC-MS/GC-FID analyses was developed for the quantitation of alkaloidal compounds in imported fire ants, Solenopsis richteri, S. invicta, and their hybrid found in the southern United States. The cis and trans alkaloids from fire ant body extracts were successfully separated by silica gel chromatography, identified by GC-MS, and quantitated by GC-FID. Piperideine compounds were eluted together with the cis and trans piperidines, but were well-resolved on a nonpolar GC column. Eight pairs of piperidine isomers and 12 piperideines were quantitated. The ratios of trans alkaloids to corresponding cis isomers ranged from 87 to 378:1 in S. invicta and were significantly higher than in S. richteri and hybrid ants. The results were discussed in relation to the evolution of fire ant venom alkaloids and their role as host location cues for parasitic Pseudacteon phorid flies.

Enhancement of attraction to sex pheromones of Spodoptera exigua by volatile compounds produced by host plants.

We measured the effects of exposure to volatile compounds produced by host plants on the rate of capture of male Spodoptera exigua using synthetic sex pheromones. Exposure to volatile compounds stimulated strong electroantennographic responses of male S. exigua. The behavioral responses of male moths to combinations of sex pheromone and volatile compounds were tested in wind tunnel experiments. When lures were baited with synthetic sex pheromone plus benzaldehyde, phenylacetaldehyde, (Z)-3-hexenyl acetate, or linalool, respectively, the landing rate of S. exigua males was increased by 101.4%, 79.6%, 60.6%, and 34.3%, respectively, compared to sex pheromone alone. In field tests, traps baited with either pheromone + (E)-2-hexenal, pheromone + phenylacetaldehyde, pheromone + (Z)-3-hexenyl acetate, or pheromone + (Z)-3-hexenol enhanced moth catches by 38.8%, 34.6%, 24.6%, and 20.8%, respectively compared to traps baited with pheromone alone. In a second field experiment, more S. exigua males were trapped with a combination of a synthetic sex pheromone blend and several individual host plant volatiles compared to synthetic sex pheromone alone. These results suggest that some host plant volatiles enhance the orientation response of S. exigua male moths to sex pheromone sources.