Studies on the genes controlling lethality and development of the silkmoth, Bombyx mori.

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We adopted genome mapping as a strategy to analyze lethal genes in the silkworm, Bombyx mori since we thought positional cloning would be the most direct pathway to access the lethal genes and other developent-controlling genes. 1. We constructed an integrated map of RAPDs, RFLPs and phenotypic loci on chromosome 22, by mating experiments. This map contains the sku lethal gene. 2. A development-controlling gene, the DH-PBAN gene, was mapped at -2.5cM on chromosome 22.3. The RAPD linkage map was corresponded to the conventional phenotypic map for chromosomes 7,13 and 18 as linkage groups. Some lethal genes such as Obs, are carried by these chromosomes. 4. A few RAPDs on the Z chromosome were cloned and sequenced. One of them was considered to be a single copy sequence. 5. Some RAPDs on chromosomes 7 and 13 were cloned and sequenced. 8. A major factor which control the life span and egg-laying behavior in strain xu20, was determined to be linked to a RAPD on the 29th RAPD linkage group. 6. Sequence divergence at synonymous and non-synonymous sites of the aryphorin gene was estimated from the bombycid and saturniid silkmoths. A phylogenetic tree based on the non-synonymous sites of the gene was proposed as an evolutionary relationship of silkmoths. 7. Messenger RNA for hexamerins were quantitated along develoment and between sexes in Samia cynthia ricini and Antheraea pernyi. 8. The polyhedrin genes of the B.mori nuclear polyhedrosis virus were sequenced for an amorphous polyhedron mutant and a cuboidal polyhedron mutant. We revealed several amino acid substitutions in the polyhedrin-encoding region.