Abstract
Silkworms (Bombyx mori) reared on artificial diets have great potential applications in sericulture. However, the mechanisms underlying the enhancement of metabolic utilization by altering silkworm nutrition are unclear. The aim of this study was to investigate the mechanisms responsible for the poor development and low silk protein synthesis efficiency of silkworms fed artificial diets. After multi-generational selection of the ingestive behavior of silkworms to artificial diets, we obtained two strains, one of which developed well and another in which almost all its larvae starved to death on the artificial diets. Subsequently, we analyzed the metabolomics of larval hemolymph by gas chromatography/liquid chromatography–mass spectrometry, and the results showed that vitamins were in critically short supply, whereas the nitrogen metabolic end product of urea and uric acid were enriched substantially, in the hemolymph of the silkworms reared on the artificial diets. Meanwhile, amino acid metabolic disorders, as well as downregulation of carbohydrate metabolism, energy metabolism, and lipid metabolism, co-occurred. Furthermore, 10 male-dominant metabolites and 27 diet-related metabolites that differed between male and female silkworms were identified. These findings provide important insights into the regulation of silkworm metabolism and silk protein synthesis when silkworms adapt to an artificial diet.
Highlights
Over 60% of pests that affect agriculture and forests are lepidopterans
Some urgent questions that need to be answered are: 1) what is the overall difference in nutrient absorption and utilization, as well as nutritional metabolism, between silkworms reared on artificial diets and those reared on mulberry leaves? 2) What is a reasonable explanation, at the metabolic level, why silkworms reared on artificial diets develop poorly and have low silk protein synthesis efficiencies? To answer these questions, here used disruptive selection to produce two genetically stable silkworm strains, one with a high artificial diet intake and another with a low artificial diet intake, from a domesticated silkworm production variety, and we analyzed the metabolomic differences in the hemolymph between silkworm larvae reared on mulberry leaves and those reared on an artificial diet
The larval stage of silkworms reared on the artificial diet was 12–13% longer than that of those reared on mulberry leaves, while the fifth instar was shortened by 11–14%
Summary
Over 60% of pests that affect agriculture and forests are lepidopterans. The silkworm Bombyx mori is considered an ideal lepidopteran model insect for scientific research[1]. Silkworms have not been reared on artificial diets during all-weather factory farming, as are livestock and poultry, as they are still reared widely on fresh mulberry (Morus) leaves This practice has hindered the improvement of sericulture resources in different areas. For almost all silkworm varieties bred so far, only the intake of artificial diets by larvae has been improved, while the metabolic utilization of artificial diets is still not as good as that of mulberry leaves. Issues such as weak silkworm larvae, low silk protein synthesis efficiency, and low silk yields in silkworms reared on artificial diets have not been resolved[6, 18]. Some urgent questions that need to be answered are: 1) what is the overall difference in nutrient absorption and utilization, as well as nutritional metabolism, between silkworms reared on artificial diets and those reared on mulberry leaves? 2) What is a reasonable explanation, at the metabolic level, why silkworms reared on artificial diets develop poorly and have low silk protein synthesis efficiencies? To answer these questions, here used disruptive selection to produce two genetically stable silkworm strains, one with a high artificial diet intake and another with a low artificial diet intake, from a domesticated silkworm production variety, and we analyzed the metabolomic differences in the hemolymph between silkworm larvae reared on mulberry leaves and those reared on an artificial diet
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