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Objectives: The silkworm Bombyx mori (B. mori) is an important domesticated lepidopteran model for basic and applied research. They produce silk fibres that have great economic value. The gut microbiome plays an important role in the growth of organisms. Spermidine (Spd) is shown to be important for the growth of all living cells. The effect of spermidine feeding on the gut microbiome of 5th instar B. mori larvae was checked. The B. mori gut samples from control and spermidine fed larvae were subjected to next-generation sequencing analysis to unravel changes in the bacterial community upon spermidine supplementation. Data description: The changes in gut bacteriota after spermidine feeding is not studied before. B. mori larvae were divided into two groups of 50 worms each and were fed with normal mulberry leaves and mulberry leaves fortified with 50 µM spermidine. The gut tissues were isolated aseptically and total genomic DNA was extracted, 16S rRNA region amplified and sequenced using Illumina platform. The spermidine fed gut samples were shown to have abundance and diversity of the phyla Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria.

The demand for silk increases as its economic value rises. Silk production by the silkworm, Bombyx mori L., is linked to the quality of the silkworm diet, leading to efforts to nutritionally enrich the mulberry (Morus alba L.) diet of silkworm larvae. Previous studies have established that spermidine, a polyamine, enhances larval growth in B. mori, subsequently increasing silk production. However, its role in improving the nutritional quality of the silkworm diet is not known. In this study, we evaluated the effects of spermidine-treated diet on the nutritional indices, polyamine levels, and antioxidant potential in fifth-instar larvae. We also assessed the effect of consumption of the spermidine-treated diet on the larval gut microbiome, which impacts digestion and assimilation of nutrients. Larvae consuming the spermidine-treated diet showed a significant increase in the efficiency of conversion of ingested food and digested food, intracellular polyamine levels (especially the conjugated and free fraction), antioxidant potential and cell viability, and both diversity and number of bacterial communities. These findings suggest that feeding mulberry leaves fortified with spermidine enhances nutritional efficiency in the B. mori larvae and may represent a method of increasing silk production by B. mori.

Background Chromatin architecture is critical for gene expression during development. Matrix attachment regions (MARs) control and regulate chromatin dynamics. The position of MARs in the genome determines the expression of genes in the organism. In this study, we set out to elucidate how MARs temporally regulate the expression of the fibroin heavy chain (FIBH) gene during development. We addressed this by identifying MARs and studying their distribution and differentiation, in the posterior silk glands of Bombyx mori during 5th instar development. Results Of the MARs identified on three different days, 7.15% MARs were common to all 3 days, whereas, 1.41, 19.27 and 52.47% MARs were unique to day 1, day 5, and day 7, respectively highlighting the dynamic nature of the matrix associated DNA. The average chromatin loop length based on the chromosome wise distribution of MARs and the distances between these MAR regions decreased from day 1 (253.91 kb) to day 5 (73.54 kb) to day 7 (39.19 kb). Further significant changes in the MARs in the vicinity of the FIBH gene were found during different days of 5th instar development which implied their role in the regulation and expression of the FIBH gene. Conclusions The presence of MARs in the flanking regions of genes found to exhibit differential expression during 5th instar development indicates their possible role in the regulation of their expression. This reiterates the importance of MARs in the genomic functioning as regulators of the molecular mechanisms in the nucleus. This is the first study that takes into account the tissue specific genome-wide MAR association and the potential role of these MARs in developmentally regulated gene expression. The current study lays a foundation to understand the genome wide regulation of chromatin during development.

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