Walter S. Leal

Walter Leal

Position Title
Distinguished Professor

Department of Molecular and Cellular Biology, College of Biological Sciences

1117 Surge III

Research Interests

Biochemical and molecular basis of insect olfaction

Research in my lab is aimed at unraveling the molecular mechanisms that make the insect’s olfactory system so sensitive and selective. Insect prominence among other animals is due in large part to a key physiological element for their survival and reproduction - a refined olfactory system. Olfaction is orchestrated at various levels starting with reception of odorants at the periphery, processing and integration of olfactory and other sensory modalities in the brain, and ultimately translation of olfactory signal into behavior. Thus, the cornerstone of a sophisticated olfactory system is the ability of the insect’s peripheral system to selectively detect and rapidly inactivate minute amounts of odorants. Reception of odorants is mainly mediated by three olfactory proteins, namely, odorant-binding proteins (OBPs or PBPs when the odorant is a pheromone), odorant receptors (ORs), and odorant-degrading enzymes (ODEs). OBPs are involved in the uptake, transport and delivery of odorants to ORs. In collaboration with structural biologists, including Drs. Kurt Wuthrich (Scripps), Jon Clardy (Harvard), David Wilson (UC Davis), Glaucius Oliva (University of Sao Paulo), and James Ames (UC Davis), we determined the 3D structures of various PBPs and OBPs from moths and mosquitoes, and unraveled their mode of action. Using stopped-flow fluorescence, our laboratory determined the kinetics of odorant binding and release by PBPs. With recombinant and native enzymes (i.e., isolated from insect antennae), we demonstrated that ODEs are involved in the rapid inactivation of chemical signals in insect antennae. By using bioinformatics, molecular approaches, RNAi, transgenic flies, and sensory physiology techniques (e.g., the Xenopus oocyte recording system; single sensillum recordings), we have identified ORs from moths, mosquitoes, and other insects, and investigated how they contribute to the selectivity of the insect’s olfactory system. One of these receptors, CquiOR136, was isolated from the southern house mosquito, Culex quinquefasciatus, and is involved in the reception of DEET as a spatial repellent (odorant). We are currently investigating other receptors that might be involved in the reception of DEET as a spatial and contact (tastant) repellent.    

Grad Group Affiliations

  • AgCHEM: Agricultural and Environmental Chemistry
  • Biochemistry, Molecular, Cellular and Developmental Biology


  • BIS 102 Struc-Func Biomolecules


  • Leal Lab
    • Pingxi Xu, Thiago Franco, Xiaolan Wen, WeiYu (James) Lu, Kaiming Tan, Justin Hwang, Xiang Meng

Honors and Awards

  • 2016: Distinguished Professor of Biochemistry, Department of Molecular and Cellular Biology; 2015: Elected a Fellow of the California Academy of Sciences; 2015: Elected Honorary Fellow of Royal Entomological Society (Hon. F.R.E.S.); 2013: Inducted into the Brazilian Academy of Sciences; elected in 2012; 2012: Silver Medal, International Society of Chemical Ecology; 2011: Fellow, Royal Entomological Society; 2011: Nan Yao Su Award for Innovation and Creativity in Entomology, ESA; 2011: National Chemical Ecology Prize Prof. Jose Tercio Barbosa Ferreira, Brazil; 2011: Guest Speaker, Advanced School of Natural Products, São Paulo, Brazil; 2011: Sawicki Lecture Honored Speaker, Rothamsted Research, United Kingdom; 2010: Guest Speaker, American Philosophical Society (Autumn Meeting); 2010: C. W. Woodworth Award, Pacific Branch-ESA; 2009: Fellow, Entomological Society of America; 2008: Recognition Award in Insect Physiology, Biochemistry, and Toxicology, ESA; 2008: Medal of Science “Mérito em Ciência,” Brazilian Society of Entomology; 2007: Silverstein-Simeone Award, International Society of Chemical Ecology; 2007: Robert L. Patton Lecture, Cornell University, Department of Entomology; 2006: Scudder Lecture Award, University of British Columbia, Canada; 2006: Gamma Sigma Delta Honor Society of Agriculture; 2005: Fellow, American Association for the Advancement of Science (AAAS); 2003: Gary Simmons Distinguished Memorial Lecture, Michigan State University, Entomology; 2002: Recognition Award in Insect Physiology, Biochemistry, and Toxicology, PB-ESA; 1998: Award of the Japanese Society of Applied Entomology and Zoology; 1995: Medal of Achievement, Entomological Society of Brazil; 1994: Technology Prize (Gijitsusho), Japan Society for Bioscience, Biotech. and Agrochemistry

Professional Societies

  • Entomological Society of America; International Society for Chemical Ecology; Japan Society for Bioscience, Biotechnology, and Agrochemistry; Japan Society of Applied Entomology and Zoology
  • American Association for the Advancement of Science (AAAS)
  • American Chemical Society
  • Royal Entomological Society


  • 1982 BS Chemical Engineering Universidade Federal de Pernambuco, Recife-PE, Brazil
  • 1987 MS Agricultural Chemistry Mie University, Tsu-Mie, Japan
  • 1990 PhD Biochemistry Tsukuba University, Tsukuba-Ibaraki, Japan -


Lu W, Hwang JK, Zeng F, Leal WS. DEET as a feeding deterrent. PLoS One. 2017;12(12):e0189243. Epub 2017/12/15. doi: 10.1371/journal.pone.0189243. PubMed PMID: 29240785.

Leal WS. Reverse chemical ecology at the service of conservation biology. Proc Natl Acad Sci U S A. 2017;114(46):12094-6. Epub 2017/11/03. doi: 10.1073/pnas.1717375114. PubMed PMID: 29093161.

Guedes DR, Paiva MH, Donato MM, Barbosa PP, Krokovsky L, Rocha S, Saraiva K, Crespo MM, Rezende TM, Wallau GL, Barbosa RM, Oliveira CM, Melo-Santos MA, Pena L, Cordeiro MT, Franca RFO, Oliveira AL, Peixoto CA, Leal WS, Ayres CF. Zika virus replication in the mosquito Culex quinquefasciatus in Brazil. Emerg Microbes Infect. 2017;6(8):e69. Epub 2017/08/10. doi: 10.1038/emi.2017.59. PubMed PMID: 28790458; PMCID: PMC5583667.

Oliveira DS, Brito NF, Nogueira FCS, Moreira MF, Leal WS, Soares MR, Melo ACA. Proteomic analysis of the kissing bug Rhodnius prolixus antenna. J Insect Physiol. 2017;100:108-18. Epub 2017/06/14. doi: 10.1016/j.jinsphys.2017.06.004. PubMed PMID: 28606853.

Paiva MHS, Guedes DRD, Leal WS, Ayres CFJ. Sensitivity of RT-PCR method in samples shown to be positive for Zika virus by RT-qPCR in vector competence studies. Genet Mol Biol. 2017;40(3):597-9. Epub 2017/05/24. doi: 10.1590/1678-4685-GMB-2016-0312. PubMed PMID: 28534930; PMCID: PMC5596374.

Carvalho WJ, Fujimura PT, Bonetti AM, Goulart LR, Cloonan K, da Silva NM, Araujo ECB, Ueira-Vieira C, Leal WS. Characterization of antennal sensilla, larvae morphology and olfactory genes of Melipona scutellaris stingless bee. PLoS One. 2017;12(4):e0174857. Epub 2017/04/20. doi: 10.1371/journal.pone.0174857. PubMed PMID: 28423045; PMCID: PMC5396885.

Hughes DT, Pelletier J, Rahman S, Chen S, Leal WS, Luetje CW. Functional and Nonfunctional Forms of CquiOR91, an Odorant Selectivity Subunit of Culex quinquefasciatus. Chem Senses. 2017;42(4):333-41. Epub 2017/03/24. doi: 10.1093/chemse/bjx011. PubMed PMID: 28334229.

Leal WS, Barbosa RM, Zeng F, Faierstein GB, Tan K, Paiva MH, Guedes DR, Crespo MM, Ayres CF. Does Zika virus infection affect mosquito response to repellents? Sci Rep. 2017;7:42826. Epub 2017/02/17. doi: 10.1038/srep42826. PubMed PMID: 28205633; PMCID: PMC5311973.

Leal WS. Zika mosquito vectors: the jury is still out. F1000Res. 2016;5:2546. Epub 2016/11/18. doi: 10.12688/f1000research.9839.1. PubMed PMID: 27853521; PMCID: PMC5105876.

Nikbakhtzadeh MR, Buss GK, Leal WS. Toxic Effect of Blood Feeding in Male Mosquitoes. Front Physiol. 2016;7:4. Epub 2016/02/10. doi: 10.3389/fphys.2016.00004. PubMed PMID: 26858651; PMCID: PMC4726748.

Nikbakhtzadeh MR, Buss GK, Leal WS. Toxic Effect of Blood Feeding in Male Mosquitoes. Front Physiol. 2016;7:4. Epub 2016/02/10. doi: 10.3389/fphys.2016.00004. PubMed PMID: 26858651; PMCID: PMC4726748.

Choo YM, Buss GK, Tan K, Leal WS. Multitasking roles of mosquito labrum in oviposition and blood feeding. Front Physiol. 2015;6:306. Epub 2015/11/19. doi: 10.3389/fphys.2015.00306. PubMed PMID: 26578978; PMCID: PMC4625056.

Xu P, Zhu F, Buss GK, Leal WS. 1-Octen-3-ol - the attractant that repels. F1000Res. 2015;4:156. Epub 2015/11/07. doi: 10.12688/f1000research.6646.1. PubMed PMID: 26543554; PMCID: PMC4623779.

Pelletier J, Xu P, Yoon KS, Clark JM, Leal WS. Odorant receptor-based discovery of natural repellents of human lice. Insect Biochem Mol Biol. 2015;66:103-9. Epub 2015/10/24. doi: 10.1016/j.ibmb.2015.10.009. PubMed PMID: 26494014; PMCID: PMC4663167.

Leal WS. Snapshot of insect-fungus arms race. Proc Natl Acad Sci U S A. 2015;112(28):8519-20. Epub 2015/07/01. doi: 10.1073/pnas.1510615112. PubMed PMID: 26124139; PMCID: PMC4507252.

Yin J, Choo YM, Duan H, Leal WS. Selectivity of odorant-binding proteins from the southern house mosquito tested against physiologically relevant ligands. Front Physiol. 2015;6:56. Epub 2015/03/17. doi: 10.3389/fphys.2015.00056. PubMed PMID: 25774136; PMCID: PMC4343023.

Franco TA, Oliveira DS, Moreira MF, Leal WS, Melo AC. Silencing the odorant receptor co-receptor RproOrco affects the physiology and behavior of the Chagas disease vector Rhodnius prolixus. Insect Biochem Mol Biol. 2016;69:82-90. Epub 2015/03/10. doi: 10.1016/j.ibmb.2015.02.012. PubMed PMID: 25747010.

Leal GM, Leal WS. Binding of a fluorescence reporter and a ligand to an odorant-binding protein of the yellow fever mosquito, Aedes aegypti. F1000Res. 2014;3:305. Epub 2015/02/12. doi: 10.12688/f1000research.5879.2. PubMed PMID: 25671088; PMCID: PMC4309172.

Leal WS. The enigmatic reception of DEET - the gold standard of insect repellents. Curr Opin Insect Sci. 2014;6:93-8. Epub 2014/12/23. doi: 10.1016/j.cois.2014.10.007. PubMed PMID: 25530943; PMCID: PMC4269249.

Xu P, Choo YM, De La Rosa A, Leal WS. Mosquito odorant receptor for DEET and methyl jasmonate. Proc Natl Acad Sci U S A. 2014;111(46):16592-7. Epub 2014/10/29. doi: 10.1073/pnas.1417244111. PubMed PMID: 25349401; PMCID: PMC4246313.

Ueira-Vieira C, Kimbrell DA, de Carvalho WJ, Leal WS. Facile functional analysis of insect odorant receptors expressed in the fruit fly: validation with receptors from taxonomically distant and closely related species. Cell Mol Life Sci. 2014;71(23):4675-80. Epub 2014/05/13. doi: 10.1007/s00018-014-1639-7. PubMed PMID: 24816944; PMCID: PMC4231014.

Vasquez GM, Syed Z, Estes PA, Leal WS, Gould F. Specificity of the receptor for the major sex pheromone component in Heliothis virescens. J Insect Sci. 2013;13:160. Epub 2014/04/30. doi: 10.1673/031.013.16001. PubMed PMID: 24773407; PMCID: PMC4015405.

Figueira-Mansur J, Ferreira-Pereira A, Mansur JF, Franco TA, Alvarenga ES, Sorgine MH, Neves BC, Melo AC, Leal WS, Masuda H, Moreira MF. Silencing of P-glycoprotein increases mortality in temephos-treated Aedes aegypti larvae. Insect Mol Biol. 2013;22(6):648-58. Epub 2013/08/29. doi: 10.1111/imb.12052. PubMed PMID: 23980723.

Choo YM, Pelletier J, Atungulu E, Leal WS. Identification and characterization of an antennae-specific aldehyde oxidase from the navel orangeworm. PLoS One. 2013;8(6):e67794. Epub 2013/07/05. doi: 10.1371/journal.pone.0067794. PubMed PMID: 23826341; PMCID: PMC3691121.

Leal, W. S., Choo, Y. M., Xu, P., da Silva, C. B., and Ueira-Vieira, C. Differential expression of olfactory genes in the southern house mosquito and insights into unique odorant receptor gene isoforms Proc. Natl. Acad. Sci. USA, October 28, 2013, doi: 10.1073/pnas.1316059110

Leal, W. S. Healing power of honey. Proc. Natl. Acad. Sci. USA May 28, 2013 vol. 110 no. 22 8763-8764

Damberger,F. D., Michel, E., Ishida, Y., Leal, W. S., and Wüthrich, K. 2013 Pheromone discrimination by a pH-tuned polymorphism of the Bombyx mori pheromone-binding protein Proc. Natl. Acad. Sci. USA, October 24, 2013, doi: 10.1073/pnas.1317706110

Zhu F, Xu P, Barbosa RM, Choo YM, Leal WS. RNAi-based demonstration of direct link between specific odorant receptors and mosquito oviposition behavior. Insect Biochem Mol Biol. 2013 Oct;43(10):916-23. doi: 10.1016/j.ibmb.2013.07.008. Epub 2013 Aug 2. PubMed PMID: 23911547.

Xu P, Leal WS. Probing insect odorant receptors with their cognate ligands: insights into structural features. Biochem Biophys Res Commun. 2013 Jun 7;435(3):477-82. doi: 10.1016/j.bbrc.2013.05.015. Epub 2013 May 11. PubMed PMID: 23673297

Xu P, Choo YM, Pelletier J, Sujimoto FR, Hughes DT, Zhu F, Atungulu E, Cornel AJ, Luetje CW, Leal WS. Silent, generic and plant kairomone sensitive odorant receptors from the Southern house mosquito. J Insect Physiol. 2013 Sep;59(9):961-6. doi: 10.1016/j.jinsphys.2013.07.004. Epub 2013 Jul 19. PubMed PMID: 23876610.

Leal WS. Odorant reception in insects: roles of receptors, binding proteins, and degrading enzymes. Annu Rev Entomol. 2013;58:373-91. doi: 10.1146/annurev-ento-120811-153635. Epub 2012 Sep 27. Review. PubMed PMID: 23020622

Xu P, Garczynski SF, Atungulu E, Syed Z, Choo YM, Vidal DM, Zitelli CH, Leal WS. Moth sex pheromone receptors and deceitful parapheromones. PLoS One. 2012;7(7):e41653. doi: 10.1371/journal.pone.0041653. Epub 2012 Jul 20. PubMed PMID: 22911835; PubMed Central PMCID: PMC3401280.

Xu P, Hooper AM, Pickett JA, Leal WS. Specificity determinants of the silkworm moth sex pheromone. PLoS One. 2012;7(9):e44190. doi: 10.1371/journal.pone.0044190. Epub 2012 Sep 5. PubMed PMID: 22957053; PubMed Central PMCID: PMC3434217

Eliyahua, D., S. Nojimaa, R. G. Santangelo, S. Carpenterc, F. X. Webster, D. J. Kiemle, C. Gemeno, W. S. Leal, and Coby Schal. 2012. Unusual macrocyclic lactone sex pheromone of Parcoblatta lata, a primary food source of the endangered red-cockaded woodpecker. Proc. Natl. Acad. Sci. USA, doi: 10.1073/pnas.1111748109

Syed, Z., and W. S. Leal. 2011. Electrophysiological measurements from a moth olfactory system. J. Vis. Exp., doi: 10.3791/2489, 2011

E. Michel, F. F. Damberger, Y. Ishida, F. Fiorito, D. Lee, W. S. Leal, and K. Wuthrich. 2011. Dynamic conformational equilibria in the physiological function of the Bombyx mori pheromone-binding protein. J. Mol. Biol.,vol. 408, pp.922-931,,doi:10.1016/j.jmb.2011.03.008

Mao, Y., X. Xu, W. Xu, Y. Ishida, W. S. Leal, J. B. Ames, and J. Clardy. 2010. Crystal and solution structures of an odorant-binding protein from the southern house mosquito complexed with an oviposition pheromone. Proc. Natl. Acad. Sci. USA, doi: 10.1073/pnas.1012274107

Leal WS. Behavioural neurobiology: The treacherous scent of a human. Nature. 2010 Mar 4;464(7285):37-8. doi: 10.1038/464037a. PubMed PMID: 20203594

Syed, Z., A. Kopp, D. A. Kimbrell, and W. S. Leal. 2010. Bombykol receptors in the silkworm moth and the fruit fly. Proc. Natl. Acad. Sci. USA, vol. 107, pp. 9436-9439, 2010.

Syed, Z., and W. S. Leal. 2009. Acute olfactory response of Culex mosquitoes to a human- and bird-derived attractant. Proc. Natl. Acad. Sci. USA, vol. 106, pp. 18803-18808, 2009.

Syed, Z. and W. S. Leal. 2008. Mosquitoes smell and avoid the insect repellent DEET. Proc. Natl. Acad. Sci. USA, 105:13598-13603.

Wogulis, M., T. I. Morgan, Y. Ishida, W. S. Leal, and D. K. Wilson. The crystal structure of an odorant binding protein from Anopheles gambiae: Evidence for a common ligand release mechanism. Biochem. Biophys. Res. Commun. 339: 157-164, 2006.

Leal, W. S., R. M. R. Barbosa, W. Xu, Y. Ishida, Z. Syed, N. Latte, A. M. Chen, T. I. Morgan, A. J. Cornel, and A. Furtado. 2008. Reverse and conventional chemical ecology approaches for the development of oviposition attractants for Culex mosquitoes. PLoS ONE, 3(8): e3045. doi:10.1371/journal.pone.0003045.

Ishida, Y. and W. S. Leal. 2008. Chiral discrimination of the Japanese beetle sex pheromone and a behavioral antagonist by a pheromone-degrading enzyme. Proc. Natl. Acad. Sci. USA 105: 9076-9080.

Syed, Z., and W. S. Leal. 2007. Maxillary Palps Are Broad Spectrum Odorant Detectors in Culex quinquefasciatus. Chem. Senses 32:727–738.

Syed, Z., Y. Ishida, K. Taylor, D. A. Kimbrell and W. S. Leal. 2006. Pheromone reception in fruit flies expressing a moth’s odorant receptor. Proc. Natl. Acad. Sci. USA 103:16538-16543.

Ishida, Y. and W. S. Leal. 2005. Rapid inactivation of a moth pheromone. Proc. Natl. Acad. Sci. USA 102:14075-14079. PNAS Cover Article:

Leal, W. S., A. M. Chen, Y. Ishida, V. P. Chiang, M. L. Erickson, T. I. Morgan, and J. M. Tsuruda. 2005. Kinetics and molecular properties of pheromone binding and release. Proc. Natl. Acad. Sci. USA 102:5386-5391.

Leal, W. S., P. H. G. Zarbin, H. Wojtasek, S. Kuwahara, M. Hasegawa, and Y. Ueda. 1997. Medicinal alkaloid as a sex pheromone. Nature 385: 213.

Leal, W. S. 1996 Chemical communication in scarab beetles: Reciprocal behavioral agonist-antagonist activities of chiral pheromones. Proc. Natl. Acad. Sci. USA 93: 12112-12115.