Control of mosquitoes and the Asian citrus psyllids using RNAi targeting JH biosynthetic pathway

In mosquitoes and the Asian citrus psyllids Juvenile Hormone (JH) plays an important role in larval and nymphs developmental stages and in adult mosquitoes egg development.  The enzyme that methylates JH III acid (JHA III) into JH III in Aedes aegypti is Juvenile Hormone Methyl Transferase (JHAMT); the ultimate enzyme in the JH biosynthetic pathway.  On the other hand, in the Asian citrus psyllid JH is synthesized from Farnesoic Acid (FA) by FA-o- methyl transferase (FA-o-MT), which was first purified by us from Hemiptera with preferred biological activity for FA and not JHA III.  Thus, both JHAMT and FA-o-MT play pivotal roles in the JH biosynthetic pathway of these insects.  To stop JH biosynthesis in  mosquitoes and psyllids we used  RNAi approach by: a). expressed long hair pin (LHP) RNA against Aedes aegypti JHAMT in transgenic Pichia pastoris yeast cells and then fed the cells to mosquito larvae or, b). expressed dsRNA in citrus tristeza virus (CTV) that replicates in the phloem of citrus, the site were the Asian citus psyllids (Diaphorina citri) feed and then allowed psyllids infected with Liberibacter asiaticus to feed on these trees. In mosquito larvae that fed transgenic Pichia pastoris cells expressing LHP RNA, adult eclosion was delayed by 3 weeks with high mortality.  A marked decrease in the number of the surviving adults was noted after feeding D. citri on citrus harboring CTV that produce dsRNA against FA-o-MT transcript as compared with feeding on control citrus trees that did not express dsRNA.  All surviving adults that were assayed by PCR were negative for L. asiaticus indicating that expressing dsRNA molecules in citrus prevents JH biosynthesis and can be highly effective against the spread of L. asiaticus by D. citri. A practical approach to control mosquito larvae and the Asian citrus psyllids will be discussed.