JBIC Journal of Biological Inorganic Chemistry

, Volume 20, Issue 8, pp 1229–1238

Mitochondrial iron supply is required for the developmental pulse of ecdysone biosynthesis that initiates metamorphosis in Drosophila melanogaster

Original Paper

DOI: 10.1007/s00775-015-1302-2

Cite this article as:
Llorens, J.V., Metzendorf, C., Missirlis, F. et al. J Biol Inorg Chem (2015) 20: 1229. doi:10.1007/s00775-015-1302-2

Abstract

Synthesis of ecdysone, the key hormone that signals the termination of larval growth and the initiation of metamorphosis in insects, is carried out in the prothoracic gland by an array of iron-containing cytochrome P450s, encoded by the halloween genes. Interference, either with iron-sulfur cluster biogenesis in the prothoracic gland or with the ferredoxins that supply electrons for steroidogenesis, causes a block in ecdysone synthesis and developmental arrest in the third instar larval stage. Here we show that mutants in Drosophila mitoferrin (dmfrn), the gene encoding a mitochondrial carrier protein implicated in mitochondrial iron import, fail to grow and initiate metamorphosis under dietary iron depletion or when ferritin function is partially compromised. In mutant dmfrn larvae reared under iron replete conditions, the expression of halloween genes is increased and 20-hydroxyecdysone (20E), the active form of ecdysone, is synthesized. In contrast, addition of an iron chelator to the diet of mutant dmfrn larvae disrupts 20E synthesis. Dietary addition of 20E has little effect on the growth defects, but enables approximately one-third of the iron-deprived dmfrn larvae to successfully turn into pupae and, in a smaller percentage, into adults. This partial rescue is not observed with dietary supply of ecdysone’s precursor 7-dehydrocholesterol, a precursor in the ecdysone biosynthetic pathway. The findings reported here support the notion that a physiological supply of mitochondrial iron for the synthesis of iron-sulfur clusters and heme is required in the prothoracic glands of insect larvae for steroidogenesis. Furthermore, mitochondrial iron is also essential for normal larval growth.

Keywords

Development Insect Mitochondria Mitoferrin Cholesterol 

Abbreviations

7DHC

7-dehydrocholesterol

20E

20-hydroxyecdysone

BPS

Bathophenanthroline disulfonate

dfh

Drosophila frataxin

dib

disembodied

dmfrn

Drosophila mitoferrin

E74A

Ecdysone-induced protein 74EF

FAC

Ferric ammonium citrate

Fer1HCH

Ferritin 1 heavy chain homolog

GFP

Green fluorescent protein

Gp93

Glycoprotein 93

Hsc20

Heat shock protein cognate 2

MRS3/4

Yeast mitoferrins

RNAi

RNA interference

Rp49

Ribosomal protein L32

sad

shadow

Tb

Tubby

Funding information

Funder NameGrant NumberFunding Note
Vetenskapsrådet
  • 621-2011-5155
Carl Tryggers Stiftelse för Vetenskaplig Forskning
  • CTS12:281 and KF14:4
Consejo Nacional de Ciencia y Tecnología of Mexico
  • #179835

Copyright information

© SBIC 2015

Authors and Affiliations

  1. 1.Department of Comparative PhysiologyUppsala UniversityUppsalaSweden
  2. 2.Heidelberg University Biochemistry Center (BZH)University of HeidelbergHeidelbergGermany
  3. 3.Departamento de Fisiología, Biofísica y NeurocienciasCentro de Investigación y de Estudios AvanzadosMexico CityMexico

Personalised recommendations