| Experimental animal is an important part of the modern life sciences research, and also the important foundation and support of modern life science research. More than one hundred years has the silkworm been used as the genetics experimental animal. With the establishment and perfection of the silkworm-related database, the silkworm, as a model insect of Lepidoptera, gets an increasing attention. The silkworm has an abundant of genetic resources, a clear genetic background and a medium body size which makes it easily to be operated. Up to now, the researches of silkworm have made a great breakthrough on lots of fields, such as gene function, developmental biology, genetics, cellular biology, bacterial infection, and the genetic resources utilization etc. And all of these mentioned above make the silkworm as a experiment animal with an increasingly extensive application.Longevity has always been the dream pursued by people, which make the lifespan to be a research focus in the life science field. Since "the lamp aging theory" presented in the thirteenth Century, lots of lifespan regulation theories have been raised and some genes and signaling pathways have also been found. Aging is a complex scientific problem, therefore it still need further research. The Rhodiola is a new anti-aging medicine discovered recently. For its multiple advantages, the Rhodiola has awalys been a research focus. But the basic mechanism of the medicine to prolong life is still not very clear yet, and more researches need to be performed..Herein, we treated the silkworm by the Rhodiola extract to investigate whether the silkworm can be used as an experimental animal for lifespan research. In this study, we observed the changes of the lifespan, growth and physiological aspects of silkworm affected by Rhodiola Extract. We also investigated the changes of the activity of anti-oxidase and the expression level of lifespan related genes in tissues of the silkworm after treatment with Rhodiola Extract, and based on which the molecular mechanism that Rhodiola Extract extend the silkworm lifespan was preliminarily analyzed and speculated. The main results are as follows:1. The effect of Rhodiola Extract on lifespan and physiological indexes of silkwormThe length of different developmental stages and several physiological indexes of the silkworm treated with the Rhodiola extract were compared with that of the untreated. The results showed that the mean time of larvae stage, pupa stage, moth stage, the whole growth period, and the highest life expectancy of female and male silkworm treated with Rhodiola Extract were significantly longer than that of the untreated group. However, the average weight, food intake, fecundity of the treated group were similar with control. Therefore, we termed the observed effect the Rhodiola Extract-mediated lifespan increases which will not influence the weight and food intake of the silkworm, and not reduce the fecundity to reduce energy consumption.2. The effect of the Rhodiola Extract on stress resistance of silkworm.We investigated the stress resistance of silkworm treated with the Rhodiola Extract, including heat stress (38℃) and hunger. The results showed that both the anti-heat and anti-starvation ability of the silkworm treated with the Rhodiola Extract markedly increased, which indicated that the extract can also increase the stress resistance of the silkworm besides the lifespan extension.3.The effects of Rhodiola extract on antioxidant enzyme activity of silkworm.The antioxidant enzyme activity in the tissues of the5th instar larvae of the Rhodiola Extract treated group and the control were assayed. The results showed that the content of GSH and the activity of CAT and GST in fat body, midgut, blood, and whole silkworm of the5th instar larvae increased after Rhodiola treatment, and the content of MDA decreased compared with the control group indicating that the Rhodiola extract induced an increase in activity of antioxidant enzymes in silkworm, which make the ability of antioxidant defense in silkworm enhancing.4. The effect of Rhodiola extract on lifespan-related genes expression of silkworm.We have determined the effect on the transcription levels of lifespan-related genes induced by Rhodiola Extract in multiple life period after4instar of the silkworm. The results showed that Rhodiola Extract increased the transcription levels of BmFoxo in the larval stage, but decreased that in the pupa stage. The transcription levels of BmPI3K and BmAMPK of silkworm treated with Rhodiola Extract significantly lowered in the whole period than that of the control group. The transcription levels of BmAKT in4st instar molting, Day1of5th instar, Oh,24h,48h after spinning initiation, Day1and Day2at the pupal stage, Day1at the Moth stage of female, Day2at the pupal stage and Day1at the Moth stage of male were lower in treated than control group. We Speculated that the IGF-1pathway may mediate the silkworm lifespan extension induced by Rhodiola extract, and the AMPK gene may involve in the regulatory pathway.In this research, we investigated the changes of silkworm lifespan, associated physical and chemical indexes and gene expression of silkworm treated by Rhodiola, and the results suggested that the silkworm can be an experimental animal to study lifespan. This can not only provide a new experimental material for the life research, but also provide a theoretical reference for study of life mechanism. |
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