Study On The Role Of Horizontally Transferred Genes DapB,dapF And LysA With Bacterial Origin In Lysine Synthesis Of The Whitefly Bemisia Tabaci

During the evolution of the symbiont in Bemisia tabaci,many essential genes were lost in its genome,which could not fully synthesize the amino acids required for B.tabaci.But horizontal transferred genes(HTGs)can compensate for or duplicate the metabolic function of symbionts with reduced genome.This study is aimed to reveal the mechanism of how horizontal transferred genes promote the lysine synthesis in the whitefly B.tabaci by evolutionary analysis,protein location,functional complementation of E.coli auxotrophs,RNA interference,amino acid level determination and so on.1.DapB,dapF and lysA in multiple B.tabaci species have the same evolutionary originMultiple B.tabaci species contain horizontal transferred genes dapB,dapF and lysA with high sequence identity.DapB,DapF and LysA from all B.tabaci species we investigated clustered in the same evolutionary branch of Rickettsia,Pantoea and Planctomycetes,respectively,indicating that they have a common evolutionary origin and these horizontal transferred genes may have convergent functions.2.Elimination of Hamiltonella induced expression of horizontal transferred genesThere was no significant difference of the lysine content between B.tabaci harboring and lacking Hamiltonella.While the expression levels of dapB,dapF and lysA were significantly up-regulated in Hamiltonella-eliminated whiteflies.It appears that Hamiltonella may provide some amount of lysine to the host or not,or even consume the lysine synthesized by the host.In the absence of the Hamiltonella,the increased expression of horizontal transferred genes may compensate for the lysine synthesized by Hamiltonella,or the horizontal transferred genes may be induced by the changes of lysine content.These results suggest that horizontal transferred genes may play an important role in the lysine synthesis of B.tabaci MEAM1.3.Proteins encoded by horizontal transferred genes are enriched in bacteriocytesDapB,DapF and LysA are located in the cytoplasm and cell membrane of bacteriocytes,and are different from the location of Hamiltonella.The different localization patterns indicate that DapB,DapF and LysA are not encoded by Hamiltonella.DapB,DapF and LysA may perform important metabolic functions in bacteriocytes.4.Horizontal transferred genes can functionally compensate for auxotrophic E.coliHomologous gene knockout mutants of E.coli BW25113 dapB,dapF and lysA prepared by lambda recombination method failed to grow normally in LB medium and M9 medium.The functional replacement of homolog E.coli genes by the whitefly horizontal transferred genes rescued the growth of E.coli BW25113 mutation.The results demonstrated that horizontal transferred genes dapB,dapF and lysA in whiteflies may have the function of synthesizing lysine.5.RNA interference of lysA reduced the lysine content and decreased the egg production of B.tabaciSilencing lysA by dsRNA injection reduced the lysine content in B.tabaci MEAM1 by27.77%,indicating that lysA is related to the synthesis of lysine.Meanwhile,gene silencing caused significant decrease of the fecundity of B.tabaci MEAM1.This study demonstrated that the horizontal transferred genes dapB,dapF and lysA are involved in the synthesis of lysine in whiteflies.The findings of this study not only provide more insight into the mechanism of coevolution and interaction between insects and symbiont,but also provide new avenues and strategies for effective control of whiteflies in the agriculture.