Mariner-like elements (MLEs) are DNA transposons that are prevalent in a wide range of eukaryotic genomes and are considered to be inserted into their host genomes via horizontal transfer. In this study, we performed a phylogenetic analysis to compare MLEs obtained from 18 species of three orders, Araneae, Hymenoptera, and Lepidoptera, with previously reported MLEs, which were classified into the mellifera subfamily. These MLEs shared high sequence similarity (92.78%). Furthermore, MLEs obtained from four distinct species contained an intact or almost intact open reading frame that encoded a putative transposase. The phylogenetic differences between these MLEs and their respective host species as well as the high sequence similarity of MLEs clearly suggests that horizontal transfer has recently occurred among species than previously reported MLEs. We discuss their possible modes of horizontal transfer based on the analysis of this study.

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In order to develop a new silkworm race that produces strong silk fibers, we investigated the physical properties of the cocoon filaments of our breeding strains, which includes a wide variation in filament size. Our strains showed the largest variation in tensile strength (3.31-4.46 gf/d), being dependent on filament size, with the weakest cocoon filament being that of “PCG”, which spins an ordinary size filament (3.8 denier). The tensile strength of the PCG cocoon filament correlated negatively with the sample length, suggesting many fragile points on the filament. A non-uniform shape with many thin constrictions was also observed in PCG cocoon filaments under microscopic analysis.

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N-glycosylation plays an important role in various biological activities and in the structural stability of serum glycoproteins. The baculovirus expression system (BES) is widely used to produce recombinant proteins but in some case it is not suitable for medical use because of the differences in N-linked glycans between insects and mammals. We reported that human serum protein alpha 1-acid protein (α1AGP) is effectively used as a model protein for evaluating the validity of engineering the insect-type N-glycosylation pathway. Using this protein, the productivity and N-linked glycan structures were compared among the 37 different silkworm strains. Interestingly, there was no difference in N-linked glycan structure among the silkworm strains, but there was difference in the degree of N-glycosylation.

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