| Silkworm(Bombyx mori)(B. mori) is a typical silk insect, complete metamorphosis,egg, larva, pupa and adult, four completely different development stages over a generation cycle. B. mori originated from the ancient chinese wild silkworm(Bombyx mandarina),and has 5 700 years of domestication history, short life cycle, smaller individuals suitable for laboratory rearing. B. mori has formed with multiple quality variety resources in long-term artificial selection, especially the new species that produce high silk yield,greatly improving the raw silk production. However, their feed efficiency is generally low,affecting their promotion and application in production.Nano materials are widely used in biology due to their unique properties, having certain biological activities, safety and non-toxic, and used as feed additive that can promote the protein degradation and absorption. Nano Ti O2(Titanium dioxide nanoparticles, Ti O2 NPs), whose structure size was between 1 and 100 nm, and because the particle size decreases the surface energy of nano Ti O2 can increase sharply, makes a small size effect, surface effect and quantum size effect and so on. Ti O2 NPs has already applied to pigment, paint, antibacterial and cosmetics additive, but has not been reported as silkworm feed additive.In order to study whether Ti O2 NPs can improve the feed efficiency of B. mori, thus increasing the amount of silk production, this article used "Suju×Minghu" as material to study the influence of Ti O2 NPs(5 mg/L) on the feed efficiency of B. mori, using digital gene expression profiling(Digital Gene Expression Profiling, DGE) technology to analysis the reason of feed efficiency changes, the main results are as follows:1 Effects of Ti O2 NPs on the feed efficiency of B. moriThrough the investigation of the feed efficiency on B. mori(the amount of ingested food, the amount of digestion, percentage of ingested food), the cocoon quality(cocoon mass, cocoon shell mass and ratio of cocoon shell) and silk quality(average cocoonfilament length, reliability, size of raw silk and neatness) data, presented the effects of Ti O2NPs(5 mg/L) on the feed efficiency of B. mori. The results showed that, after being treated by Ti O2 NPs, all number were increasing, including the amount of ingested food which was increased by 3.254%, percentage of ingested food by 16.373%, the instar by 6.756 h,the body mass of mature silkworm by 11.231%, cocoon mass by 5.601%, cocoon shell mass by 9.318% and the ratio of cocoon shell by 3.521%. Additionally, average cocoon filament length, reelability and neatness were increased by 3.152%, 17.574% and 1.717%,respectively, whereas the cocoon filament size was decreased by 0.192%, showed that feeding Ti O2 NPs can not only improve the feed efficiency of silkworm, increase the cocoon yield, but also improve the silk quality.2 Analysis of DGE data in the midgut of B. mori after Ti O2 NPs treatmentIn order to investigate the reasons why Ti O2 NPs would improve the feed efficiency of B. mori, midgut of B. mori at fifth instar in the third day were used as the materials for DGE analysis. Through transcription and expression profile data to analysis the molecular mechanism of Ti O2 NPs improve the feed efficiency of B. mori. The DGE results showed that 4 011 genes were detected, 127 genes were differentially expressed including 57 genes whose expression was up-regulated and 70 genes whose expression was down-regulated,and these genes were classified through GO and KEGG comments. This study used Real Time PCR to verify the expression levels of 6-phosphogluconate dehydrogenase, serine protease precursor, 35 K protease, glutamate dehydrogenase and ATP synthase, showed the same results with DGE. The activities of three major digestive enzymes in midgut were also assayed, presented that the activities of trehalase, protease and lipase in Ti O2 NPs group were increased by 42.553%, 78.125% and 33.333% respectively. The results of this study showed that Ti O2 NPs enhanced the activity of enzymes associated with digestion,increased the digestion and absorption of the midgut to mulberry leaves, eventually increased the amount of ingested food, the amount of digestion, as well as the body mass.This study showed that, feeding B. mori with Ti O2 NPs can improve the activity of digestive enzymes in midgut, improve the feed efficiency of silkworm, increase the cocoon yield, and have a certain reference value to improve the economic benefits of sericulture. |
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