Toru Shimada

The nonsusceptibility (complete resistance) to Bombyx mori densonucleosis virus type-1 (BmDNV-1) of the silkworm is controlled by a recessive gene, nsd-1, in the 21st linkage group. The +nsd-1is a dominant DNV-1 susceptibility gene. We constructed the CSD-1 strain, congenic strain of the C137 (nsd-1/nsd-1) for the 21st linkage group, starting with a female of the C137 and a male of the J137 ( +nsd-1+nsd-1). Since crossing over is restricted to males in the silkworm, the CSD-1 strain is maintained by repeated backcrossing of the males of C137 to the nsd-1/ + females. CSD-1 strain contains susceptible (nsd-1/ + ) and nonsusceptible (nsd-1 /nsd-1) larvae at a 1 : 1 ratio. Some random amplified polymorphic DNAs (RAPDs) in the 21st linkage group of the J137 have been found previously. In order to develop the diagnosis method for the susceptibility of the CSD-1 larvae without virus inoculation and killing, we used these RAPD markers. DNAs extracted from the abdominal legs of 4th instar larvae after ligation, or legs of moths, were individually used as templates for polymerase chain reaction (PCR). We could distinguish the susceptible individuals from the nonsusceptible ones. This diagnosis method is useful for detecting the DNV-1 susceptible individuals without virus inoculation and for obtaining the next generation of diagnosed ones. © 1996, The Japanese Society of Sericultural Science. All rights reserved.

We have already established a diagnostic technique based on the polymerase chain reaction to detect nuclear polyhedrosis virus in a silkworm population using samples containing the wastes and feces as well as larval bodies. In the present study, we utilized potassium acetate precipitation instead of phenol/chloroform treatment at the deproteinization step of DNA extraction, thus avoiding danger of applying a large amount of organic solvents. Also HCl treatment of DNA followed by ethanol precipitation was found to be effective to increase the diagnostic sensitivity. By using this improved method, we could detect a single polyhedrosis-infected larva in a 0.5, 1 and 3 kg sample for the 1st, 2nd and 3rd instar, respectively. © 1995, The Japanese Society of Sericultural Science. All rights reserved.

We have constructed a linkage map of random amplified polymorphic DNAs (RAPDs) in Bombyx mori. We screened 320 10-mer primers, and found 243 clear polymorphic bands between C108 and p50 strains. In the F2 generation, segregation ratios of 168 bands were nearly 3:1 in a chi square test, showing Mendelian inheritance. The MAPMAKER program sorted 168 bands into 29 linkage groups and 10 unlinked loci at minimum LOD score 3·0, and determined orders of loci in each group, which contained 2–11 markers. It also detected typing errors in our data. We calculated map distances between pairs of neighbouring loci using recombination values in males and the Kosambi mapping function. Our RAPD map consists of 169 loci including the p locus, and the sum of map distances is approximately 900 cM. Linkage groups 1 and 2 of our map correspond to chromosomes 1 and 2 on the conventional linkage map because of linkage to sex and p, respectively. © 1995, Cambridge University Press. All rights reserved.

The sex chromosome formula of the silkworm, Bombyx mori, are designated ZW (XY) for the female and ZZ (XX) for the male. In order to identify random amplified polymorphic DNA (RAPD) derived from the T(W 2)+P chromosome onto which the normal larval marking gene (+P) was translocated to the W chromosome, individual genomic DNAs from males and females of the Chinese 137 strain (Dp(2 W)+P, p/p) were used as templates for the polymerase chain reaction and about 400 random primers (10-mers) were screened on this strain. As the result one RAPD was found to be ubiquitous in females and absent in all males. This female-specific RAPD is thus located on the T(W 2)+P chromosome and will be useful for analyses of the W chromosome. © 1995, The Japanese Society of Sericultural Science. All rights reserved.

We examined the developmental changes of the sericin components in different sections of the middle silkgland of Bombyx mori by acid-polyacrylamide gel electrophoresis. The components of sericin which wee separated in to S1, S, S3, S3, S4, and fiactions S5, changed quantitatively depending on developmental stage and the section of the gland. They were detected as follows: S1, in the middle sections from the 2nd day of the 5th instar until spinning and in the anterior section from the 4th day of the 5th instar until spinning S, in the middle section on the 2nd-4th day of the 5th instar and in the anterior section from the 4th day until spinning S8, in the middle section from the 4th instar until the 3rd day of the 5th instar and in the anterior sections from the 4th instar until the 5th day of the 5th instar S3, in the middle section on the 3rd-7th day of the 5th instar and in the anterior section on the second day of spinning S4, in the posterior sections from the 4th day of the 5th instar until spinning, in the middle section from the 7th day of the 5th instar until spinning and in the anterior section from the 2nd day of spinning S5, in the middle sections from 4th instar until the 6th day of the 5th instar and in the anterior section an the 1st and 2nd day of spinning. These results suggest that each component is secreted from a specific section of the middle gland at a specific developmental stage and is transported from the posterior to the anterior part in the silkgland. © 1992, The Japanese Society of Sericultural Science. All rights reserved.

Arylphorins are major serum proteins in larvae of holometabolous insects. We studied cross-reaction of arylphorins from 11 silkworm species with anti-Samia cynthia ricini and anti-Bombyx mori arylphorin sera by Oudin's single immunodiffusion and Ouchterlony's double immunodiffusion analyses. Species used were 1. S. c. ricini, 2. S. c. pryeri, 3. Antheraea yamamai, 4. Antheraea pernyi, 5. Dictyoploca japonica, 6. Actias selene, 7. B. mori, 8. B. mandarina, 9. Prismosticia hyalinata, 10. Pseudandraca gracilis, and 11. Oberthueria falcigera. Species 1-6 belong to Saturniidae, and 7-11 to Bombycidae. Intensity of cross-reaction with anti-S. c. ricini serum was arranged in the order as follows: 1=2>3=4=5=6=9 greater-than-or-equal-to 10=11>7=8. That with anti-B. mori was as follows: 7=8>1=2=3=4=5=6=9=10=11. These results indicates that similarity of arylphorins is highest between 1 and 2 and between 7 and 8, and that arylphorins of 3, 4, 5, 6, 9, 10 and 11 are more similar to the arylphorin of 1 than that of 7. We discussed the phylogenetic relationship among these species, based on the results.

Differences in properties of storage proteins, SP-1 and SP-2, among genetic variants in the silkworm, Bombyx mori were examined. In three variants of SP-1, type B and type C gave single bands supposed to be hexamers on polyacrylamide gel electrophoresis (PAGE), but electrophoretic mobility of type B was larger than that of type C. On the other hand, type A gave many bands, which proved to be a hexamer and various larger polymers. On SDS-PAGE, no difference was detected among these variants. Isoelectric point of type C was higher than those of other types, and a small difference in peptidemapping patterns was observed between type C and others. Variation of SP-2 were detected in two races, Kansen and Ascoli according to mobilities on PAGE. On SDS-PAGE, SP-2 of Kansen gave two bands, while that of Ascoli gave a single.band corresponding to larger subunit of SP-2 in Kansen. © 1985, The Japanese Society of Sericultural Science. All rights reserved.

Larval haemolymph proteins in many strains of the silkworm, Bombyx mori were analyzed on polyacrylamide gel electrophoresis, and polymorphic variations of electrophoretic mobilities of storage proteins, SP-1 and SP-2 were investigated. Three variants in SP-1, and two or more variants in SP-2 were found. Mating experiments showed that the variation of SP-1 is controlled by multiple alleles at a locus locating on the twenty-third chromosome and is manifested codominantly. Another mating experiment between two races whose electrophoretic mobilities of SP-2 were different from each other showed that the variation of SP-2 is controlled by a pair of codominant alleles linked with Zebra (Ze) which had been mapped on the third chromosome. © 1985, The Japanese Society of Sericultural Science. All rights reserved.