Ye-Rim Son

Immunosuppression induced by entomopathogens is rescued by addition of apolipophorin III in the diamondback moth, Plutella xylostella.

Apolipophorin III (ApoLpIII) has been known to play critical roles in lipid transport and immune activation in insects. This study reports a partial ApoLpIII gene cloned from the diamondback moth, Plutella xylostella. It showed that the gene was expressed in all developmental stages of P. xylostella. In larval stage, it was expressed in all tested tissues of hemocyte, fat body, gut, and epidermis. In response to bacterial challenge, the larvae showed an enhanced level of ApoLpIII expression by a quantitative real-time RT-PCR. RNA interference of ApoLpIII by its specific double stranded RNA (dsRNA) caused significant knockdown of its expression level and resulted in significant suppression in hemocyte nodule formation in response to bacterial challenge. However, larvae treated with the dsRNA exhibited a significant recovery in the cellular immune response by addition of a recombinant ApoLpIII. Parasitization by an endoparasitoid wasp, Cotesia plutellae, suppressed expression of ApoLpIII and resulted in a significant suppression in the hemocyte nodule formation. The addition of the recombinant ApoLpIII to the parasitized larvae significantly restored the hemocyte activity. Infection of an entomopathogenic bacterium, Xenorhabdus nematophila, caused potent pathogenicity of P. xylostella. However, the addition of the recombinant ApoLpIII to the infected larvae significantly prevented the lethal pathogenicity. This study suggests that ApoLpIII limits pathogenicity induced by parasitization or bacterial infection in P. xylostella.

The Complete Mitochondrial Genome of Grapholita molesta (Lepidoptera: Tortricidae)

ABSTRACT The complete mitochondrial DNA (mtDNA) sequence of the oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), has been identified. The mtDNA (15,717 bp) of G. molesta encodes 13 putative proteins, two rRNAs, and 22 tRNAs. Analysis of nucleotide composition of the genome indicates high A+T composition (80.74%), which results in biased codon use and richness in specific amino acids of mitochondrial proteins. All protein-coding genes are initiated by ATN codons except for COI, which is initiated presumably by CGA codon. Except tRNASer (AGN), the remaining 21 tRNAs form a typical cloverleaf structure. An intergenic space between tRNASer (AGN) and ND1 contains a lepidopteran-characteristic sequence (ATACTAA). The control region, rich in A+T, harbors several sequence characteristics shared by lepidopteran species, such as the motif ATAGA followed by 5′ poly T stretch and 3′ poly A stretch at just upstream of tRNAMet. The phylogenetic analysis, using whole mtDNAs, showed that G. molesta is clustered with other tortricid species, in which lepidopterans form a monophylogeny on the basis of Papilionoidea.

Parasitism of Cotes/a plutellae Alters Morphological and Biochemical Characters of Diamondback Moth, Plutella xylostella

Abstract A solitary endoparsitoid, Cotesia plutellae, has been regarded as a major biological regulator to manipulate field population of diamondback moth (DBM), Plutella xylostella. It parasitizes DBM and alters its physiology into a favorable condition for the parasitoid development. This research has been focused on the physiological changes in terms of internal morphology and biochemical changes of the parasitized DBM. The parasitized DBM exhibited significantly hypotrophied structures in Malpighian tubules, fat body, and testes, while it did not show apparent change in the digestive organ structure. The parasitoid represented almost 70% of total body weight of the parasitized DBM. This estimate was well corresponded to the measurements of the major nutrient amounts in the parasitized DBM. This study clearly indicates that the major nutrients obtained by the parasitoid DBM are exploited by the koinobiont parasitoid for its own development.

Analysis of migration of the oriental fruit moth, Grapholita molesta, in apple-cultivating areas based on population monitoring using sex pheromone and RAPD molecular marker.

Local and seasonal populations of the oriental fruit moth, Grapholita molesta, were monitored with sex pheromone trapping and RAPD (random amplified polymorphic DNA) molecular marker to analyze their movement in apple orchards. To detect their movements among farms, pheromone traps were placed at regions between apple farms (`outside-farms`) as well as within-farms (`inside-farms`). Four seasonal adult peaks were evident in apple-cultivating fields from April to October in both trappings of inside- or outside-farms. After overwintering generation, populations of inside-farms were significantly reduced with frequent insecticide applications, compared to populations of outside-farms. Within apple farms, G. molesta tended to be unevenly distributed because of significant sublocal preference. Active movements of local and seasonal populations of G. molesta were supported by gene flow analysis using RAPD marker. Monitoring data using sex pheromone and seasonal reduction in initial genetic differentiation detected in the overwintering populations suggest that there must be significant movement of G. molesta among different orchards in apple-cultivating areas.

Genetic Differentiation of Overwintering Populations of Oriental Fruit Moth, Grapholita molesta, and Their Movement

Spring phonology of the oriental fruit moth, Grapholita molesta, was monitored using sex pheromone traps in apple cultivating areas. Their occurrence was earlier in southern areas and their population sizes were significantly different among orchards even in a local cultivating zone. The overwintering populations appeared to move between local orchards, based on the fact that monitoring data obtained at the sites between orchards were similar to those of nearby orchards. However, within orchards, these adult movements appeared to decrease and showed skewed occurrences at the side of upwind direction or close to neighboring orchards. At initial occurrence peak(April 20-25), the ovenvintering populations of the different localities were collected and analyzed in their genetic distances. PCR-RAPD analysis indicated that there were significant genetic differences among the overwintering populations of G. molesta. This genetic differentiation of overwinterin populations may be due to genetic bottleneck following differential selection pressures against the subpopulations of G. molesta during winter on the basis of the RAPD analysis that each early spring population was significantly different to its previous fall population in the same locality.

Controlled Atmosphere and Temperature Treatment System to Disinfest Fruit Moth, Carposina sasakii (Lepidoptera: Carposinidae) on Apples

ABSTRACT Carposina sasakii Matsumura (Lepidoptera: Carposinidae) is a serious pest of apples and peaches in Korea and Japan. Because of its limited distribution, C. sasakii has been identified as a quarantine pest in several countries. The Controlled Atmosphere/Temperature Treatment System (CATTS) was tested as an alternative to methyl bromide fumigation to control C. sasakii in apples. The fifth instar was the most tolerant immature stage to a heat treatment of 44°C for 20 min. When the apples infested with different stages of C. sasakii were treated under CATTS conditions (heating rate of 16°C/h, chamber temperature of 46°C, final core temperature of 44°C under 1% O2/15% CO2 atmosphere), young larvae (first-fourth instars) did not survive after 40 min exposure, but the fifth instars required an exposure of at least 60 min to attain 100% mortality. A partial heat shock protein 90 (hsp90) was cloned and showed inducible expression in response to heat shock at 44°C. CATTS suppressed transcription of the hsp90 gene. Apples did not show any appreciable loss of quality in relation to fruit firmness, sweetness, and decay after a 60 min CATTS treatment. These results suggest that CATTS can be applicable to control C. sasakii in apples.

Applicability of CATIS as a Postharvest Phytosanitation Technology against the Peach Fruit Moth, Carposina sasakii Matsumura

As an environment-friendly phytosanitary measure, CATTS (controlled atmosphere temperature treatment system) has been developed to kill several quarantine insect pests infesting subtropical agricultural commodities. This study tested any possibility to apply CATTS to apples to effectively eliminate the peach fruit moth, Carposina sasakii, which has been regarded as a quarantine insect from the imported countries. When the larvae of C. sasakii were directly exposed to (an installed lethal temperature of CATTS), they showed a median lethal time at 14.66 min. Addition of high carbon dioxide to the temperature treatment enhanced the thermal limit susceptibility of C. sasakii to . CATTS device was constructed to automatically control concentration and temperature with real-time monitoring both in the chamber and in the fruit. The larvae internally infesting apples were tested using the CATTS device and showed 100% lethality after 60 min exposure to a treatment of under 15% in the chamber. Relatively long exposure may be due to the deviation between the ramping temperature (/min) of the chamber and the ramping temperature (0.12-/min) inside apple fruit, where the tested larvae were located. This study suggests a possibility that CATTS can be applied as a quarantine measure to kill the larvae of C. sasakii locating inside the apples.

A Molecular Marker Discriminating the Soybean Podworm, Matsumuraeses phaseoli and the Podborer, M. falcana (Lepidoptera: Tortricidae)

Two closely related species, the soybean podworm, Matsumuraeses phaseoli, and the podborer, M. falcana, gives differential economic damages on crops. It is difficult to discriminate these potential sympatric species by morphological characters. The goal of this study was to develop a discriminating molecular marker based on polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). A partial genomic fragment (500 bp) of mitochondrial cytochrome oxidase I (mtCOI) was sequenced in both species, in which restriction site by Rsa I was selected as a dichotomous marker. PCR-RFLP in the mtCOI region clearly discriminated both species.

Control Effect of a Stored Grain Insect Pest, Tribolium castaneum, by `CATTS` Postharvest Treatment

A postharvest treatment called CATTS (controlled atmosphere and temperature treatment system) has been used as an alternative nonchemical measure for methyl bromide fumigant treatment. This study applied CATTS to control the red flour beetle, Tribolium castaneum, infesting stored grains. Adults of T. castaneum were susceptible to heat treatment. The susceptibility was further enhanced by addition of CA conditions (15% and 1% ). When CATTS (, 15% , treating rate) was applied to different developmental stages of T. castaneum, it showed 100% control efficacy by 120 min exposure. There was a variation in CATTS susceptibility among developmental stages, in which late instar larvae were most tolerant. Heat shock proteins of T. castaneum appeared to be implicated in the tolerance of CATTS.

Control Efficacy of Controlled Atmosphere and Temperature Treatment System Against the Hawthorn Spider Mite, Tetranychus viennensis

The hawthorn spider mite, Tetranychus viennensis, is a pest of apples and a quarantine pest from some countries that import apples from Korea. A controlled atmosphere and temperature treatment system (CATTS) was developed as an alternative disinfestation method to methyl bromide fumigation treatment, and has been applied to control various insects and other arthropod pests on fruits. We applied CATTS to disinfect T. viennensis under conditions that were previously developed to control the peach fruit moth, Carposina sasakii. First, T. viennensis was sampled from Japanese apricot, Prunus mume, and identified by its morphological characters. In addition, both cytochrome oxidase I (COI) and internal transcribed spacer (ITS) sequences supported the morphological identification. Second, the heat-tolerant developmental stage was determined in T. viennensis. When a heat treatment was applied to egg, nymph, and adult stages of T. viennensis, adults were the most tolerant stage. Third, when heat temperature was used along with 1% and 15% , the mites showed a significant increase in susceptibility to the heat treatment. Finally, CATTS at with 15% and 1% for 30 min resulted in 100% mortality of all T. viennensis development stages. These results indicated that CATTS isapplicable to disinfest T. viennensis in post-harvest apples.