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Heterochromatin protein 1s (HP1s) are nonhistone chromosomal proteins that play a direct role in the formation and maintenance of heterochromatin structure. Similarly to Caenorhabditis elegans, silkworms possess holocentric chromosomes, in which diffused kinetochores extend along the length of each chromosome. We have isolated two silkworm HP1 homologues, BmHP1a and BmHP1b. Cytological analysis showed a unique localization of BmHP1s during cell division, in which these proteins first appear to dissociate from the chromosomes, but then return to enclose the chromosomes during metaphase. BmHP1s formed homo- and hetero-dimers and interacted with BmSu(var)3-9, which is a methyltransferase for histone H3 lysine 9 (H3K9). We further showed, using a silkworm cell-based reporter system, that BmHP1b had higher transcriptional repression activity than BmHP1a, whereas BmHP1a interacted more strongly with BmSu(var)3-9 than did BmHP1b. These results suggest that silkworm HP1a and HP1b may play different roles in heterochromatin formation in holocentric silkworm chromosomes.

Epigenetic information is encoded in post-translational modifications (PTMs) of histones. Various combinations of these marks contribute to the regulation of chromatin-templated DNA metabolisms. The histone code is gradually translated into biological responses in model organisms. However, in the silkworm, the modifications of histones with unique holocentric chromosomes have not yet been analyzed. TAU-PAGE analysis of the silkworm histone variants H2A, H2B, and H3, separated by RP-HPLC, suggested silkworm specific modification. Detailed mass spectrometry analyses of the peptides derived from the N-terminus of the silkworm H3.2 generated by glutamyl endopeptidase, lysyl endopeptidase, and trypsin digestions revealed global modifications around H3K9.

The amount of dietary fiber (neutral detergent fiber, acid detergent fiber and lignin) in the edible portion; leaf, stalk and bud; of 53 species of wild plants was determined by Van Soest method and also the amounts of crude fiber, water, fat and ash of these plants were estimated. These plants were taken in Fukushima prefecture and belonged to Compositae, Liliaceae, Umbelliferae, Polypodiaceae, Araliaceae, Cruciferaeae, Uruticaceae, Polygonaceae, Caprifoliaceae, Equisetaceae, Rosaceae, Lardinabalaceae, Campanulaceae, Leguminosae, Chenopodiaceae, Saururaceae, Plantaginaceae, Berberidaceae, Saxifragaceae, Rutaceae, Gramineae, Actinidiaceae and Clethraceae.Takadiastase digestion of plant before analysis of neutral detergent fiber had little effect on the amount of neutral detergent fiber in leaf, stalk and bud of wild plants. The amounts of neutral detergent fiber, acid detergent fiber and crude fiber of these plants were 1.07 to 5.92%, 0.79 to 5.19% and 0.64 to 3.67% respectively. The correlation (r) of c ude fiber with neutral detergent fiber, acid detergent fiber and cellulose; the difference between acid detergent fiber and lignin; were 0.63, 0.65 and 0.77 respectively. Neutral detergent fiber had a little correlation with nitrogen free extract (r=-0.64) but no correlation with protein and ash (r=-0.24, 0.22).