We examined the role of carotenoid-binding protein (CBP) in yellow cocoon pigmentation. First, using yellow or white cocoon races, we investigated the linkage between the yellow pigmentation and CBP expression. CBP was expressed only in the silk gland of the yellow cocoon races, which utilize carotenoids for cocoon pigmentation. Furthermore, CBP expression in the silk glands of day 1-7 fifth instar larvae matched the period of carotenoid uptake into the silk gland. Finally, we gave double-stranded CBP RNA to Bombyx mori (B. mori) larvae to induce RNA interference. The significantly reduced expression of CBP in the silk gland of fifth instar larva was confirmed on day 4 and a decrease in yellow pigmentation was observed in the cocoon. We showed that CBP plays a key role in the yellow cocoon pigmentation caused by carotenoids.

In deletion-mapping of W-specific RAPD (W-RAPD) markers and putative female determinant gene (Fem), we used X-ray irradiation to break the translocation-carrying W chromosome (W( Ze )). We succeeded in obtaining a fragment of the W( Ze ) chromosome designated as Ze (W), having 3 of 12 W-RAPD markers (W-Bonsai, W-Yukemuri-S, W-Yukemuri-L). Inheritance of the Ze (W) fragment by males indicates that it does not include the Fem gene. On the basis of these results, we determined the relative positions of W-Yukemuri-S and W-Yukemuri-L, and we narrowed down the region where Fem gene is located. In addition to the Ze (W) fragment, the Z chromosome was also broken into a large fragment (Z(1)) having the +( sch ) (1-21.5) and a small fragment (Z(2)) having the +( od ) (1-49.6). Moreover, a new chromosomal fragment (Ze (W)Z(2)) was generated by a fusion event between the Ze (W) and the Z(2) fragments. We analyzed the genetic behavior of the Z(1) fragment and the Ze (W)Z(2) fragment during male (Z/Z(1) Ze (W)Z(2)) and female (Z(1) Ze (W)Z(2)/W) meiosis using phenotypic markers. It was observed that the Z(1) fragment and the Z or the W chromosomes separate without fail. On the other hand, non-disjunction between the Ze (W)Z(2) fragment and the Z chromosome and also between the Ze (W)Z(2) fragment and the W chromosome occurred. Furthermore, the females (2A: Z/Ze (W)Z(2)/W) and males (2A: Z/Z(1)) resulting from non-disjunction between the Ze (W)Z(2) fragment and the W chromosome had phenotypic defects: namely, females exhibited abnormal oogenesis and males were flapless due to abnormal indirect flight muscle structure. These results suggest that Z(2) region of the Z chromosome contains dose-sensitive gene(s), which are involved in oogenesis and indirect flight muscle development.

We have discovered an inordinately large chromosome pair at the pachytene stage in the oocyte of the sex-limited p B (black larval marking) silkworm (Bombyx mori) strain (TWPB). We have analyzed the composition and arrangement of this large chromosome. A genetic linkage analysis shows that the large chromosome is made up of the W chromosome, the second chromosome fragment (p fragment), and the fifth chromosome (linkage group) containing at least the region from map position 0.0 to 40.8. We also observed a sex heterochromatin body (SB) that we deduced to be made up of condensed W chromosomes. The number of SBs in each female nucleus among the sucking stomach cells of the TWPB strain was variable. Evidently, the W chromosome of the TWPB strain is attached to another chromosome. The composition of the W chromosome, the second chromosome fragment, and the fifth chromosome was studied through linkage analysis for these three chromosomes. We used two strains derived from the TWPB strain, the sex-limited p M (moricaud barVal marking)-hke (TWPML) and the autosomal p M-like (TSPML). The results show that the TWPML strain originates through a detachment of the fifth chromosome from the large chromosome of the TWPB strain, and the TSPML strain originates through a detachment of the W chromosome from that. Accordingly, the large chromosome of the TWPB strain is arranged in the order W chromosome-second chromosome fragment-fifth chromosome.

The purpose of this study was to investigate the effects of calcium carbonate and saccharides on the feeding behavior of newly hatched larvae of the silkworm, Bombyx mori L. Japanese strains, "Hi", "KAI", "Ryo" and "Yo", and Chinese strains, "Kai", "Bono", "Kenpaku" and "Tsukuba", were used for the experiments. Calcium carbonate (CaCO 3) and sucrose were added to the basal diet, consisting of cellulose powder, agar and distilled water. This was fed to the larvae immediately after they hatched. It was found that the feeding of any variety of silkworm was improved by the synergetic effects of CaCO 3 and sucrose. The amount of feeding for "Kai" and "Bono", however, were notably less than those of the other varieties. Next, diets containing CaCO 3 and two kinds of saccharides were fed to both the "Kai" and "Bono". The amount of diet consumed by "Kai" and "Bono" remarkably increased when CaCO 3 was used together with sucrose and myo-inositol, and CaCO 3 together with glucose and myo-inositol, respectively. The above results indicated that CaCO 3 combined with sucrose or other saccharides synergistically stimulated larval appetite. Also it was found that CaCO 3 could restrict larval movement to the area immediately surrounding the diet.