Expression Profiling,Functional Verification And Potential Regulation Of Vitellogenin Gene During Ovary Development In An Invasive Pest Octodonta Nipae

Octodonta nipae is an important pest of palm trees,strong reproductive capacity is a prerequisite for its successful colonization.Vitellogenin is one of the most important precursors of yolk protein that synthesized mainly in fat body,secreted into hemolymph and finally sequestered by competent oocytes by receptor-mediated endocytosis,deposited as vitellin(Vt)in oocytes as the main source of nutrients for developing embryos.Vg Plays an important role in insect reproduction.However,the synthesis mechanism of Vg in O.nipae is not well know,and the further studies on molecular regulation mechanism of Vg are important for effective control of this pest.Therefore,this study investigated the dynamic expression of Vg during ovarian development and the effect of Vg on ovarian development,studied the regulation of juvenile hormone(JH)on the synthesis of Vg.The main results are outlined below.(1)Virgin female adults at 0,5,10,15 and 20 d after eclosion were collected and dissected,their ovary development level were evaluated based on related parameters.The ovaries of O.nipae were gradually developed after emergence,and egg yolk began to accumulate in the ovary;RT-qPCR and ELISA showed that with the development of ovaries,the expression level of Vg in the whole body gradually increased,and Vg was continuously enriched in the ovary;the Vg knockdown by RNAi caused a significant decrease in ovariole width and ovarian cross-sectional area but not ovariole length,indicating that Vg affect ovarian morphological development.(2)JH plays an important role in regulating the expression of Vg.The expression profile of juvenile hormone acid methyl transferase(JHAMT),which is involved in JH synthesis,is similar to Vg expression,besides,knockdown of JHAMT changed the level of Vg mRNA,indicate JHAMT is related to the expression of Vg,suggesting that JH participates in the transcription of Vg gene.Interesting,the relative expression level of Methoprene-tolerant(Met),which is a receptor of JH is stable,and RNAi of Met did not reduce the relative expression of Vg but changed the relative expression of Kruppel-homolog 1(kr-hl),which participate in metamorphosis,speculating that Met may not or partially participate in the regulation of Vg transcription by JH in the O.nipae.In conclusion,Vg is an important storage protein in O.nipae that can promote the ovarian development,and JHAMT regulates the expression of Vg by participating in the synthesis of JH.However,the role of Met in the regulatory process remains to be further studied.