Reactive oxygen species detoxification by catalase is a major determinant of fecundity in the mosquito Anopheles gambiae

doi:10.1073/pnas.0608407104

Reactive oxygen species detoxification by catalase is a major determinant of fecundity in the mosquito Anopheles gambiae

*Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Rockville, MD 20852-8132; and
^†Department of Microbiology, Immunology, and Pathology, Colorado State University, 1619 Campus Delivery, Ft. Collins, CO 80523

Edited by John H. Law, University of Georgia, Athens, GA, and approved December 28, 2006 (received for review September 25, 2006)

Abstract

The mosquito Anopheles gambiae is a primary vector of Plasmodium parasites in Africa. The effect of aging on reproductive output in A. gambiae females from three strains that differ in their ability to melanize Plasmodium and in their systemic levels of hydrogen peroxide (H₂O₂), a reactive oxygen species (ROS), was analyzed. The number of eggs oviposited after the first blood meal decreases with age in all strains; however, this decline was much more pronounced in the G3 (unselected) and R (refractory to Plasmodium infection) strains than in the S (highly susceptible to Plasmodium) strain. Reduction of ROS levels in G3 and R females by administration of antioxidants reversed this age-related decline in fecundity. The S and G3 strains were fixed for two functionally different catalase alleles that differ at the second amino acid position (Ser2Trp). Biochemical analysis of recombinant proteins revealed that the Trp isoform has lower specific activity and higher K _m than the Ser isoform, indicating that the former is a less efficient enzyme. The Trp-for-Ser substitution appears to destabilize the functional tetrameric form of the enzyme. Both alleles are present in the R strain, and Ser/Ser females had significantly higher fecundity than Trp/Trp females. Finally, a systemic reduction in catalase activity by dsRNA-mediated knockdown significantly reduced the reproductive output of mosquito females, indicating that catalase plays a central role in protecting the oocyte and early embryo from ROS damage.

Footnotes

^‡To whom correspondence should be addressed at:
Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases/National Institutes of Health, MSC 8132, Twinbrook III, Room 2E-20, Bethesda, MD 20892-8132.
E-mail: cbarillas{at}niaid.nih.gov
Author contributions: R.J.D., A.M.-C., and C.B.-M. designed research; R.J.D., L.M.M., A.M.-C., L.G., and S.K. performed research; R.J.D. analyzed data; and R.J.D. and C.B.-M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS direct submission.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. DQ980199–DQ980210 and DQ986315).
This article contains supporting information online at www.pnas.org/cgi/content/full/0608407104/DC1.
Abbreviations:

AT,

3-amino-1,3,4-triazole;

DAB,

diaminobenzidine;

PBM,

post-blood meal;

PE,

post-emergence;

ROS,

reactive oxygen species;

SOD,

superoxide dismutase.