Inheritance And Pigment Basis Of Larval Body Color Of Chinese Oak Silkworm,Antheraea Pernyi

Chinese oak silkworm(Antheraea pernyi)is a unique agricultural insect resource in China that can be used as silk producer(cocoons),edible resource(pupae,larvae and moths).It has already been considered a new type of ornamental insect due to the diversity of the larval body color.In production and breeding practice,larval body color has long been used as the basic morphological marker for selection.In order to analyze the genetic and pigment basis of larval body color,the pigment related genes in the larval epidermis were identified by transcriptome sequencing,the temporal and spatial changes of the total carotenoid content were detected,the genetic analysis of larval yellow and white body colors was carried out,and the carotenoid components and contents in the larval epidermis between the two types were compared by metabolomics method.The results of this study provide basic information for further exploring the regulation mechanism of the larval body color formation and genetic improvement of varieties.1.The color of the epidermis between A.pernyi and Bombyx mori showed great differences.Then,this study compared the transcriptome of the epidermis of the two silkworms to explore the genetic basis behind the difference.Based on the transcriptome data of the epidermis,a total of 8,710 differentially expressed genes were identified,which was consistent with the great difference in the epidermis.In the transcriptome data,100 and 69 pigment related genes involved in 11 pigment pathways were identified in A.pernyi and B.mori epidermis,respectively.Genes related to flavones and pteridine pathways were represented in A.pernyi larval epidermis,but not in B.mori epidermis.More genes involved in biliverdin,rhodopsin and carotene pathways were identified in A.pernyi than in B.mori.Genes related to six pigment pathways including melanin,heme,eye pigment,ommochrome,adenine and purine were almost identical between the two silkworms.The results showed that the great difference in epidermis color between the two silkworms was probably caused by the changes of five pigment pathway related genes,including flavonoids,pteridine,biliverdin,rhodopsin and carotenoid.2.The changes of the total carotenoid content in A.pernyi for four developmental stages,different tissues,and varieties with different larval body colors were determined.The results showed that all the four developmental stages were rich in carotenoids,with the highest in pupal stage(112.56 ± 4.12 μg/g)and the lowest in egg stage(53.17 ± 1.67 μg/g).The deposition and distribution of carotenoids were tissue-specific in larva,with the highest in fat body(184.73 ± 6.55 μg/g)and the lowest in silk gland(39.28 ± 2.28 μg/g);the contents between epidermis and midgut were similar,with values of 144.52 ± 11.14 μg /g and 134.76 ±4.67 μg /g respectively.The content of the total carotenoids in pupal hemolymph was also variety-specific,with the highest for green silkworm(12.49 ± 2.90 g/L)and the lowest for white silkworm(4.92 ± 1.14 g/L).The total carotenoid content also exhibited heterosis.The results provide basic information for exploring the formation mechanism of the diversity of larval body color and developing new functional food for oak silkworm industry.3.In this study,Yuda＿1(yellow body color)and Baiyihua(white body color with slightly yellow)were used to carry out the genetic analysis,and the carotenoid components and contents in the larval epidermis were also compared.The results of hybridization test showed that the larval yellow body color was completely dominant to the white color.The putative white body color genotype of Baiyihua was YYgg,and the yellow body color genotype of Yuda＿1 was YYGG(yellow when Y and G coexist).Metabonomics analysis showed that the total carotenoid content of Yuda＿1(10.259 μg/g)was much higher than that of Baiyihua(1.167 μg/g);the contents of lutein,β-carotene and zeaxanthin in the epidermis of Baiyihua were much lower than those in Yuda＿1.It is supposed that the white body color of A.pernyi larvae might be caused by the shortage of the carotenoids in the epidermis.Our study provides useful information on the genetic mechanism for the diversity of body color in A.pernyi larvae.