Methyl farnesoate plays a dual role in regulating Drosophila metamorphosis.

Di Wen,Stephen S Tobe,Crisalejandra Rivera-Perez,Ola Zyaan,Qianyu He,Jingjing Xu,Qiangqiang Jia,Subba R Palli,William G Bendena,Sheng Li,Xi Liu,Fernando G Noriega,Mohamed Abdou,Jian Wang

doi:10.1371/journal.pgen.1005038

Abstract

Corpus allatum (CA) ablation results in juvenile hormone (JH) deficiency and pupal lethality in Drosophila. The fly CA produces and releases three sesquiterpenoid hormones: JH III bisepoxide (JHB3), JH III, and methyl farnesoate (MF). In the whole body extracts, MF is the most abundant sesquiterpenoid, followed by JHB3 and JH III. Knockout of JH acid methyl transferase (jhamt) did not result in lethality; it decreased biosynthesis of JHB3, but MF biosynthesis was not affected. RNAi-mediated reduction of 3-hydroxy-3-methylglutaryl CoA reductase (hmgcr) expression in the CA decreased biosynthesis and titers of the three sesquiterpenoids, resulting in partial lethality. Reducing hmgcr expression in the CA of the jhamt mutant further decreased MF titer to a very low level, and caused complete lethality. JH III, JHB3, and MF function through Met and Gce, the two JH receptors, and induce expression of Kr-h1, a JH primary-response gene. As well, a portion of MF is converted to JHB3 in the hemolymph or peripheral tissues. Topical application of JHB3, JH III, or MF precluded lethality in JH-deficient animals, but not in the Met gce double mutant. Taken together, these experiments show that MF is produced by the larval CA and released into the hemolymph, from where it exerts its anti-metamorphic effects indirectly after conversion to JHB3, as well as acting as a hormone itself through the two JH receptors, Met and Gce.

Highlights

Juvenile hormones (JHs) are members of a family of sesquiterpenoid compounds synthesized primarily by the corpus allatum (CA) of insects
The potential role of Methyl farnesoate (MF) as a JH in arthropods has been an issue of a long-standing debate
These studies showed that jhamt1 and jhamt2 are null alleles

Summary

Introduction

Juvenile hormones (JHs) are members of a family of sesquiterpenoid compounds synthesized primarily by the corpus allatum (CA) of insects. Several forms of JH have been identified, including JH 0, JH I, 4-methyl JH I, JH II, JH III, JH bisepoxide (JHB3) and JH skipped bisepoxide. JHB3 is unique to higher Diptera, such as the fruit fly, Drosophila melanogaster [2], and JH skipped bisepoxide has been described in Heteroptera [3]. Methyl farnesoate (MF) is the major sesquiterpenoid identified in the hemolymph of crustaceans, in which it might play the role of a JH [4]. The potential role of MF as a true JH in insects has been an issue of a long-standing debate; it has JH activity in the Drosophila white puparial bioassays and is abundant in the hemolymph of several insects [5,6,7,8,9,10]

Methods

Results

Discussion

Conclusion