Metabolomics Analysis Reveals The Basis For Metabolic Adaptation To High Royal Jelly Production

High royal jelly producing bees(HRJBs),a stock of honeybees selected from Italian bees(ITBs),have developed stronger ability to produce royal jelly than ITBs without changing the non-volatile components and proteins in royal jelly.However,the volatile components and its odor quality remains unknown,which affects the overall evaluation of royal jelly quality.Royal jelly is the secretion of hypopharyngeal and mandibular gland,the function of which is regulated by brain.Therefore,these three tissues are closely related to royal jelly yield,but their metabolic regulation basis is still not clear.It restricts the development and utilization of this excellent germplasm resource.In view of the above scientific problems,this paper compares the volatile components of royal jelly produced by ITBs and HJBs,and compares the metabolic profile of brain,hypopharyngeal and mandibular gland of ITBs and HRJBs newly emerged bees(NEBs),nurse bees(NBs)and forager bees(FBs).The volatile metabolic profile difference between royal jelly produced by ITBs and HRJBs is mainly reflected by the content of volatile components rather than the overall composition.A total of 37 differential volatile components are identified and several of them are discovered in royal jelly for the first time.There is no statistical difference in odor quality between royal jelly produced by ITBs and HRJBs.Compared to ITBs,the odor quality of royal jelly produced by HRJBs doesn't change significantly with the increase of yield,indicating that the increase of yield doesn't change its original flavor.A total of 248 metabolites,including amino acids,fatty acids,adenosine and other metabolites,are identified in brain,hypopharyngeal and mandibular gland of ITBs(including NEBs,NBs and FBs).The result reveals that the developmental stage mainly affects choline,amino acids,organic acids and fatty acids in tissues and most of them show the highest content in tissues of NEBs.Pathway analysis shows that several metabolic pathways,including amino acid metabolism,aminoacyl-t RNA biosynthesis,glycerophospholipid metabolism,sphingolipid metabolism and TCA cycle,are affected the most by different developmental stages.The most affected pathways are those related to energy metabolism.Similar with ITBs,the metabolic profile of brain,hypopharyngeal,mandibular of RJBs are significantly different among three developmental stages of RJBs.The differential metabolites are mainly amino acids,fatty acids,adenosine and organic acids.Compared to NEBs and FBs,the most up-regulated metabolites in tissues of NBs are acetylcholine,UDP,N-acetyl valine,UDPGA and so on.The result of metabolic pathway analysis shows that NBs of HRJBs provides support for high royal jelly yield by enhancing signal transduction,amino acid metabolism and fatty acid metabolism.In order to adapt to the high royal jelly yield,the metabolic profile of brain,hypopharyngeal,mandibular gland of HRJBs are reshaped,and the content of some fatty acids,amino acids and choline increase.The result of metabolic pathway analysis shows that pathways related to energy metabolism,amino acid metabolism,fatty acids synthesis and aminoacyl-t RNA biosynthesis in HRJBs are enhanced,constituting the metabolic basis for the improvement of royal jelly but the maintenance of good quality.In this study,we analyze the difference of metabolic profile of brain,hypopharyngeal and mandibular gland of ITBs and HRJBs in different developmental stages,and reveals that the metabolic adaption characteristic and regulatory basis of high royal jelly yield of HRJB,providing the basis for further development and utilization of germplasm resource of HRJBs.