The Main Pigment Accumulation Pattern Of Different Yellow-red Cocoons Strains In Bombyx Mori

Recently, there are two kinds of chromatic silkworm cocoons:yellow-red cocoon strains, and green cocoon strains which were preserved in China. Yellow-red cocoon strains include straw yellow, golden yellow, flesh, red, rusty and so on. The formation mechanism of yellow cocoon has been identified that the pigment material, carotenoids are transported from the midgut, though the blood, to the middle silk gland, and bind with sericin. The process is regulated by gene Y, I and C. In the past, the transportation mechanism of carotenoids in yellow cocoons was researched mainly. There are varieties of colorful strains in yellow-red cocoon strains.The main pigment of them come from mulberry leaves,but the color is significantly defferent. It is still unclear why is the chromatic difference between strains.In order to study the chromatic difference in different kinds of yellow-red cocoon strains, it is first clear that how many types and contents there are in cocoons, what the major pigments are, how they varies in silkworm body, which tissue and period the change of chromatic difference. We studied about these issues. The main results are followed.1. Optimization of the carotene extraction methods. The carotenoids in tissuse of silkworm are extracted by two common methods, after that, ether was used to further extract in order to select effect extractants. The results show that:after extracting the sample by extractant B (Hexane:Ethanol:Actone= 2:1:1),low-phase was extracted again with ether (the fourth method) and become colorless,that is the fourth method is completely obtained the carotenoids from the sample.2. The cocoon color is mainly determined by the types of coloration pigments. The carotenoids were isolated and identified in the mulberry leaves and a variety of cocoons by reversed-phase high-performance liquid chromatography. It is resulted that there are all kinds of carotenoids in the mulberry leaves and cocoon silk, but the main coloration pigments of them are same, they are violaxanthin, lutein, and p-carotenoid.3. The accumulation pattern of the coloration pigments in silkworm's tissues. We detected the major coloration pigments in the midgut, blood and silk gland of four types of cocoon color, eight strains of 5th instar larvae. We found:with the growth of instar. Except from Xiafang and 03-210, in the other six strains, the midgut and blood absorbing the carotenoids basically follow the rule: lutein> violaxanthin>β-carotenoid>α-carotenoid. The Silk gland of different strains selectedly accumulate someone carotenoids:the contens of lutein are the highest in golden cocoons, the lower isβ-carotenoid and and violaxanthin; the contents ofβ-carotenoid are the highest in red cocoons, the lower is lutein and violaxanthin; Although rusty cocoons are inclined to accumulateβ-carotenoid, it is less than the latter. The contents of carotenoids in different tissues gradually increase. This accords with dieting law. With the growth of instar, the contents silkworm ate mulberry leaves increased. The law applies to any one of silkworm varieties.4. The silk gland wall is the primary barriers of the metabolic process on different carotenoids. Through the statistical analysis of absorption and transfer to different tissues in the same strain of some pigment. We know that the silk gland wall is the primary barriers of the metabolic process on different carotenoids. The silk gland selectedly absorbs different carotenoids mainly lead to the difference of the cocoon coloration.The differences of pigment varieties are not obvious among the different color cocoons.But it is sharply different about the pigment contents and relative ratio of all kinds of colorful cocoons.It is slightly different about the pigment contents and relative proportion of different silkworm varieties with the same color.