Annual Report 2003

medium that depends on Bombyx mori eggextract instead of Fetal Bovine Serum. Theprimary culture is now under way. Althoughwe have successfully established numerouscell lines from various lepidopteran species,the use of the cells has been limited. Inorder to expand the use and to develop thecells as a research tool for analysis of insectspecificgene functions, we are characterizingthe immune-responsiveness of elevenBombyx mori cell lines. The cells were transfectedwith a plasmid containing an antibacterialcecropin B promoter followed by aluciferase reporter gene (Fig. 3). Using thissystem, several bacteria responsive cell lineswere identified and the elicitor componentsessential to bacterial cell walls were determined.These cell lines were also used toidentify novel immune-related genes, and todate eight clones have been isolated.Fig. 4Continuous silkworm freezing system.Fig. 5New silkworm breeds of coloring cocoons.Left: Green cocoon “PNG × PCG”, Center: Ordinary strain,Right: Yellow cocoon “PNY × PCY”Development of a system to produceuseful materials from the silkwormWe developed a system to produce usefulmaterials from the silkworm. To achieveincreased efficiency in extracted hemolymphfrom the silkworm using the freezing andmelting method, it is important to freezesilkworm larva into a straight stick shape.Therefore, a continuous silkworm larvafreezing system was developed.This system is composed of a thermalinsulating tank, conveyer belt, liquid coolingunit and a controller. The dimensions of thetank are 1150 mm Length × 300 mm Width ×230 mm Depth and the length of the conveyerbelt is 1250 mm. Belt speed can be controlledfrom 0.5 mm/s to 3 mm/s and dippingduration can be adjusted from 210 s to 1400s. The cooling unit has the ability to lowerliquid temp to –20˚C. The tank has a highthermal insulating function using a singlefoam polyethylene heat insulator. The temperaturewas maintained for 2 hours underthe ambient air at 25˚C without cooling unitoperation. Silkworm larvae took on astraight stick shape within 5 min under 10˚Cwater and were frozen in –10˚C liquid withina few min. It was thus confirmed that thissystem was able to freeze silkworm larvaeinto a straight stick shape continuously.Identification of the source ofmicrosporidian infectionMicrosporidian spores were detected fromthe dead larvae of Antheraea pernyi rearedoutdoors, and similar spores were alsodetected in the larvae of Lepidogma kiiensiscaught on Quercus acutissima. Analysis ofthe biological and serological featuresrevealed that these microsporidian were ofthe same lineage as Vairimorpha sp. M12spores derived from B. mori. This partiallyexplains the previously unknown route ofinfection of B. mori by M12.Breeding of silkworm races withspecial featuresWe produced silkworm breeds secretinghigh concentrations of sericin with flavonoid92 Annual Report 2003