Electroantennogram and behavioral responses of Cotesia plutellae to plant volatiles

Plant volatiles have been demonstrated to play an important role in regulat- ing the behavior of Cotesia plutellae, a major larval parasitoid of the diamondback moth （DBM）, Plutella xylostella, but little is currently known about the function of each volatile and their mixtures. We selected 13 volatiles of the DBM host plant, a cruciferous veg- etable, to study the electroantennogram （EAG） and behavioral responses of C. plutellae. EAG responses to each of the compounds generally increased with concentration. Strong EAG responses were to 100 μL/mL of trans-2-hexenal, benzaldehyde, nonanal and cis-3- hexenol, and 10/zL/mL of trans-2-hexenal and benzaldehyde with the strongest response provoked by trans-2-hexenal at 100μL/mL. In the Y-tube olfactometer, C. plutellae, was significantly attracted by 1μL/mL of trans-2-hexenal and benzaldehyde.β-caryophyllene, cis-3-hexenol or trans-2-hexenal significantly attracted C. plutellae at 10μL/mL, while nonanal, benzyl alcohol, cis-3-hexenol or benzyl cyanide at 100μL/mL significantly at- tracted C. plutellae. Trans-2-hexenal significantly repelled C. plutellae at 100 μL/mL. EAG of C. plutellae showed strong responses to all mixtures made of five various com- pounds with mixtures 3 （trans-2-hexenal, benzaldehyde, nonanal, cis-3-hexenol, benzyl cyanide, farnesene, eucalyptol） and 4 （trans-2-hexenal, benzaldehyde, benzyl alcohol, （R）- （＋）-limonene,β-ionone, farnesene, eucalyptol） significantly attracting C. plutellae. These findings demonstrate that the behavior of C. plutellae can be affected either by individual compounds or mixtures of plant volatiles, suggesting a potential of using plant volatiles to improve the efficiency of this parasitoid for biocontrol ofP. xylostella.

Characterization of a myrosinase cDNA from Brassica parachinensis and its defense role against Plutella xylostella after suppression

In Brassicaceae, myrosinase catalyzes the hydrolysis of glucosinolate and plays an important role in anti-herbivore defense. We have cloned and characterized the full- length complementary DNA of myrosinase gene from Brassicaparachinensis that exhibits high sequence identity with myrosinase genes from other Brassica species. To investigate the role of this myrosinase in defense against the diamondback moth （Plutella xylostella）, we constructed an RNA-interference （RNAi） cassette expressing a double-stranded RNA that targeted myrosinase and transfected it into B. parachinensis. Myrosinase was sup- pressed in the resulting transgenic plants. Diamondback moth larvae feeding on transgenic plants had lower larval and pupal weights, longer pupal duration, and lower fecundity than those feeding on non-transgenic plants, suggesting that the diamondback moth has adapted to the glucosinolate-myrosinase defensive system. Therefore, the suppression of myrosinase is a potential approach for controlling the diamondback moth.

Cell Iines from diamondback moth exhibiting differential susceptibility to baculovirus infection and expressing midgut genes

Abstract Six new cell lines were established from embryonic tissues of the diamondback moth, Plutella xylostella (L.). The cell lines showed differential characteristics, including growth in attachment or in suspension, susceptibility to a baculovirus infection and expression of genes involved in the glucosinolate detoxification pathway in R xylostella larvae. Five of the cell lines grew attached to the culture flask and one cell line grew unattached as a suspension cell line. The cell lines had population doubling times ranging from IS to 23 h. Among five of the P. xylostella cell lines examined for infection of a nucleopolyhe. drovirus from Autographa californica, AcMNPV four cell lines were highly susceptible to AcMNPV infection, but one was only semi-permissive to AcMNPV infection. The production of two recombinant proteins, a β-galactosidase of bacterial origin and a secreted alkaline phosphatase of eukaryotic origin, in the R xylostella cell lines was examined in comparison with that in the cell line Sf9 which is commonly used for recombinant protein production. In the P. xylostella cell lines, expression of three important midgut genes involved in the glucosinolate detoxification pathway, including the glucosinolate sulfatase genes GSS1 and GSS2 and the sulfatase modifying factor gene SUMF1、was detected. The R xylostella cell lines developed in this study could be useful in in vitro research systems for studying insec-virus interactions and complex molecular mechanisms in glucosinolate detoxification and insect-plant interactions.

Structure and expression of sulfatase and sulfatase modifying factor genes in the diamondback moth,Plutella xylostella

The diamondback moth,Plutella xylostella (L.),uses sulfatases (SULF)to counteract the glucosinolate-myrosinase defensive system that cruciferous plants have evolved to deter insect feeding.Sulfatase activity is regulated by post-translational modi- fication of a cysteine residue by sulfatase modifying factor 1(SUMF1).We identified 12 SULF genes (PxylSulfs)and two SUMF1 genes (PxylSumfls)in the P.xylostella genome. Phylogenetic analysis of SULFs and SUMFs from P.xylostella,Bombyx mori,Manduca sexta,Heliconius melpomene,Danaus plexippus,Drosophila melanogaster,Tetranychus urticae and Homo sapiens showed that the SULFs were clustered into five groups,and the SUMFs could be divided into two groups.Profiling of the expression of PxylSulfs and Pxyl Sumfs by RNA-seq and by quantitative real-time polymerase chain reaction showed that two glucosinolate sulfatase genes (GSS),PxylSulf2and PxylSulf3,were primarily expressed in the midgut of 3rd-and 4th-instar larvae.Moreover,expression of sulfatases PxylSulf2, PxylSulf3 and PxylSulf4 were correlated with expression of the sulfatases modifying fac tor PxylSumfla.The findings from this study provide new insights into the structure and expression of SUMF1and PxylSulf genes that are considered to be key factors for the evolutionary success ofP.xylostella as a specialist herbivore of cruciferous plants.

Higher taxa as surrogates of species richness of spiders in insect-resistant transgenic rice

Biodiversity assessments can often be time- and resource-consuming. Several alternative approaches have been proposed to reduce sampling efforts, including indicator taxa and surrogates. In this study, we examine the reliability of higher taxon surrogates to predict species richness in two experimental rice fields of Fujian Province, southeastern China during 2005 and 2009. Spider samples in transgenic and nontransgenie plots were collected using a suction sampler. Both the genus and family surrogates had significant and positive linear relationships with species richness in the transgenic and nontransgenic rice fields. The rice varieties did not significantly influence the linear relationships. Our findings suggest that higher-taxon surrogacy could be a useful alternative to complete species inventory for risk assessments of transgenic rice.

Identification and characterization of odorant binding proteins in the diamondback moth,Plutella xylostella

Odorant binding proteins(OBPs)are a group of soluble proteins functioning as odorant carriers in insect antennae,mouth parts and other chemosensory organs.However,multiple insect OBPs have been detected in other tissues and various functions have been proposed.Therefore,a detailed expression profile including stages,tissues and sexes where OBPs are expressed will assist in building the links to their potential functions,enhancing the functional studies of insect OBPs.Here,we identified 39 putative OBP genes from its genome and transcriptome sequences of diamondback moth(DBM),Plutella xylostella.The expression patterns of identified PxylOBPs were further investigated from eggs,larvae,pupae,virgin adults,mated adults,larval midgut,larval heads,adult antennae,adult heads and adult tarsi.Moreover,P.xylostella larvae and adults with and without host plants for 5 h were utilized to study the interactions between OBP expression and host plants.The results showed that most PxylOBPs were highly expressed in male and female adult antennae.The expression levels of certain PxyOBPs could be regulated by mating activities and feeding host plants.This study advances our knowledge of P.xylostella OBPs,which may help develop new strategies for more environmentally sustainable management of P.xylostella.

Population characteristics of Macrocheles glaber (Acari: Macrochelidae) and Stratiolaelaps scimitus (Acari: Laelapidae) reared on a mushroom fly Coboldia fuscipes (Diptera: Scatopsidae)

Subterranean predatory mites are important biological control agents of pests in soil. In order to understand the population characteristics of two predatory mites, Macrocheles glaber Miiller and Stratiolaelaps scimitus Womersley, we studied their development, survival and fecundity data under laboratory conditions using Coboldia fuscipes Meigen as a food source and analyzed them with the age-stage, two-sex life table. Macrocheles glaber had a significantly shorter developmental time, oviposition period, longevity and lower fecundity than those of S. scimitus. The intrinsic rate of increase (λ), finite rate of increase (r), net reproductive rate (C0),net predation rate (C0), and finite predation rate (ω) of M. glaber were significantly lower than those of S. scimitus. Both population parameters and computer simulation implied that S. scimitus is a potential powerful biocontrol agent compared to M. glaber.