| Heterosis, or hybrid vigor were widely applied in the production of livestocks. However, the researches for molecular mechanisms underlying the phenomenon are inadequate in the animals and not well understood. When using the liverstock to do reseach we had to under restrictions of spend, test cycle, population quantum and some other factors. Therefore, we examined heterosis for body weight and reproduction in model organisms-Drosophila melanogaster by performing RNA-seq analyses in order to explain the causes of heterosis, heterosis related pathways and candidate genes and the research methods of heterosis for livestock and poultry.This study used six drosophila strains for 6 x 6 complete diallel cross experiment, heterosis rate were calculated and tested.3 groups, including ♂WT*♀eyw,♂W1118*♀Wt and ♂eyw*♀WT, in 30 cross combinations with the heterosis for both body-weight and reproductive traits were selected. Fl hybrids and their parental inbred lines of these 3 groups were applied for sequencingWe compared the mRNA profiles of the parental and hybrid lines using high-throughput RNA-seq. A total of 5877 differentially expressed genes (DEGs) were found. The method of function classification was used in each hybrid and its parents, and carbohydrate metabolism, fat synthesis pathway were enriched in the results. In addition, insect hormone synthesis pathway were enriched in multiple groups, and DEGs which in this pathway were Juvenile hormone epoxide hydrolase (JHEH) that acted in the process of juvenile hormone (JH) catabolism.In order to understand the role of JH in heterosis, we added pyriproxyfen, juvenile hormone analogues (JHA), to the medium. As shown in the results, when the concentration were 100ng/L and 200ng/L the Drosophila could develop into pupa, but unabled to feather. At the same time, the size of pupa were significantly increased. By measuring the length, while width and weight of the pupa, we found that no significant change in the length, width increased significantly and weight showed a trend of increase; when the concentration were 10ng/L and 20ng/L Drosophila can feather normal. All the pure lines had significant changes compared to the control, and in hybrid on the contrary. There were no change regularity in the results of quantitation PCR detection for JHEH 1,2,3 and Juvenile hormone esterase (JHE). Then we speculated that maybe whole optimization occurring in the process of JH metabolism.Classification analysis for the DEGs which identified by RNA-seq were completed, and about 92% of these exhibited parental expression level dominance were functionally characterized. The analysis for dominance DEGs in each groups associated with crucial processes in all three crosses, such as growth, development and reproduction. Functional assignments involving aminoglycan metabolism, starch and sucrose metabolism, and galactose metabolism are significantly overrepresented amongst the 215 common dominance DEGs. Total of 18 genes were identified, which can be used as candidate genes to Drosophila heterosis for body-weight and reproduction traits.The results for gene expression bias analysis found that some genes occurred expression bias, and the number of male bias and female bias were similar. Comparing the two reciprocal cross combinations we found that the number of same strains bias was more than the same gender bias. Then we conducted function enrichment analysis for the same bias genes and found that Hippo signaling pathway may play an important role for heterosis of Drosophila. In addition, fat gene as a candidate gene were identified in this pathway. After that, new genes which expressed in hybrid but not expressed in inbrid were picked out, and 19 genes met the requirement in the three groups at the same time may have important effects on heterosis, especially for FBgn026358 and FBgn0262367genes. The results above can provide the basis for study of heterosis of Drosophila, and may establish new ideas for the heterosis research of livestock. |
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