title: Embryonic desiccation resistance in Aedes aegypti: presumptive role of the chitinized serosal cuticle.
abstract: BACKGROUND
  One of the major problems concerning dengue transmission is that embryos of its main vector, the mosquito Aedes aegypti, resist desiccation, surviving several months under dry conditions. The serosal cuticle (SC) contributes to mosquito egg desiccation resistance, but the kinetics of SC secretion during embryogenesis is unknown. It has been argued that mosquito SC contains chitin as one of its components, however conclusive evidence is still missing.
  
  
  RESULTS
  We observed an abrupt acquisition of desiccation resistance during Ae. aegypti embryogenesis associated with serosal cuticle secretion, occurring at complete germ band extension, between 11 and 13 hours after egglaying. After SC formation embryos are viable on dry for at least several days. The presence of chitin as one of the SC constituents was confirmed through Calcofluor and WGA labeling and chitin quantitation. The Ae. aegypti Chitin Synthase A gene (AaCHS1) possesses two alternatively spliced variants, AaCHS1a and AaCHS1b, differentially expressed during Ae. aegypti embryonic development. It was verified that at the moment of serosal cuticle formation, AaCHS1a is the sole variant specifically expressed.
  
  
  CONCLUSIONS
  In addition to the peritrophic matrix and exoskeleton, these findings confirm chitin is also present in the mosquito serosal cuticle. They also point to the role of the chitinized SC in the desiccation resistance of Ae. aegypti eggs. AaCHS1a expression would be responsible for SC chitin synthesis. With this embryological approach we expect to shed new light regarding this important physiological process related to the Ae. aegypti life cycle.
authors.affiliation: Laboratório de Fisiologia e Controle de Artrópodes Vetores, Instituto Oswaldo Cruz, FIOCRUZ and Laboratório de Entomologia, Instituto de Biologia do Exército, Rio de Janeiro, Brazil. rezendeg@ioc.fiocruz.br
authors.forename: Gustavo Lazzaro
authors.initials: GL
authors.lastname: Rezende
authors.forename: Ademir Jesus
authors.initials: AJ
authors.lastname: Martins
authors.forename: Carla
authors.initials: C
authors.lastname: Gentile
authors.forename: Luana Cristina
authors.initials: LC
authors.lastname: Farnesi
authors.forename: Marcelo
authors.initials: M
authors.lastname: Pelajo-Machado
authors.forename: Alexandre Afrânio
authors.initials: AA
authors.lastname: Peixoto
authors.forename: Denise
authors.initials: D
authors.lastname: Valle
mesh_terms: D000330:Aedes / Q000737:chemistry / Q000196:embryology* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D002686:Chitin / Q000737:chemistry / Q000502:physiology*; D002687:Chitin Synthase / Q000096:biosynthesis / Q000235:genetics; D003715:Dengue / Q000635:transmission; D003890:Desiccation; D004527:Egg Proteins / Q000737:chemistry / Q000235:genetics; D005260:Female; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics; D008969:Molecular Sequence Data; D010063:Ovum / Q000737:chemistry / Q000254:growth & development*; D012326:RNA Splicing; D013997:Time Factors
chemical_list: D004527:Egg Proteins; D019476:Insect Proteins; C047663:cuticle proteins, insects; D002686:Chitin; D002687:Chitin Synthase
references.citation: Bull Entomol Res. 1949 Mar;39(Part 4):467-88
references.pmid: 18117674
references.citation: Dev Genes Evol. 2000 Apr;210(4):167-79
references.pmid: 11180819
references.citation: Proc Natl Acad Sci U S A. 1996 Aug 6;93(16):8479-84
references.pmid: 8710895
references.citation: Annu Rev Biochem. 1973;42(0):541-74
references.pmid: 4599386
references.citation: Dev Genes Evol. 1999 Mar;209(3):145-54
references.pmid: 10079357
references.citation: J Comp Physiol B. 2006 Jan;176(1):1-15
references.pmid: 16075270
references.citation: Cryobiology. 1996 Feb;33(1):149-62
references.pmid: 8812094
references.citation: Dev Biol. 2004 Nov 15;275(2):435-46
references.pmid: 15501229
references.citation: Tissue Cell. 2003 Apr;35(2):101-12
references.pmid: 12747932
references.citation: Dev Growth Differ. 2001 Dec;43(6):725-33
references.pmid: 11737153
references.citation: Development. 2007 Jul;134(13):2415-24
references.pmid: 17522157
references.citation: Insect Mol Biol. 2006 Jun;15(3):363-72
references.pmid: 16756555
references.citation: Insect Biochem Mol Biol. 2006 Sep;36(9):712-25
references.pmid: 16935220
references.citation: Science. 2007 Jun 22;316(5832):1718-23
references.pmid: 17510324
references.citation: Curr Genet. 2002 Sep;41(6):367-78
references.pmid: 12228806
references.citation: J Insect Physiol. 1999 Oct;45(10):915-922
references.pmid: 12770284
references.citation: Tissue Cell. 2001 Dec;33(6):580-95
references.pmid: 11827102
references.citation: Dev Cell. 2005 Sep;9(3):423-30
references.pmid: 16139230
references.citation: Insect Biochem Mol Biol. 2002 Nov;32(11):1497-506
references.pmid: 12530217
references.citation: J Insect Physiol. 1999 Aug;45(8):701-708
references.pmid: 12770300
references.citation: Dev Biol. 2005 Sep 15;285(2):330-9
references.pmid: 16098962
references.citation: Curr Biol. 2005 Apr 12;15(7):R245-7
references.pmid: 15823522
references.citation: Development. 2006 Jan;133(1):163-71
references.pmid: 16339194
references.citation: J Insect Physiol. 1965 Mar;11:337-45
references.pmid: 14330765
references.citation: Curr Biol. 2005 Apr 12;15(7):624-36
references.pmid: 15823534
references.citation: J Bacteriol. 1995 Mar;177(6):1419-24
references.pmid: 7883697
references.citation: Mol Biol Evol. 1999 Dec;16(12):1675-86
references.pmid: 10605110
references.citation: Insect Biochem Mol Biol. 2005 Jul;35(7):789-98
references.pmid: 15894194
references.citation: Insect Biochem Mol Biol. 2004 Mar;34(3):291-304
references.pmid: 14871625
references.citation: Cryobiology. 1996 Feb;33(1):142-8
references.pmid: 8812093
references.citation: J Morphol. 2005 Jun;264(3):339-62
references.pmid: 15838850
references.citation: Dev Biol. 2006 Apr 1;292(1):226-43
references.pmid: 16460723
references.citation: Mem Inst Oswaldo Cruz. 2002 Jun;97(4):589-96
references.pmid: 12118297
references.citation: Proc Natl Acad Sci U S A. 2002 Jan 8;99(1):274-9
references.pmid: 11773616
references.citation: Infect Immun. 1975 Nov;12(5):987-92
references.pmid: 1104488
references.citation: J Morphol. 2005 Apr;264(1):117-30
references.pmid: 15747378
references.citation: Genetics. 2002 May;161(1):171-82
references.pmid: 12019232
references.citation: Insect Mol Biol. 2005 Oct;14(5):453-63
references.pmid: 16164601
references.citation: Insect Biochem Mol Biol. 2005 Jun;35(6):529-40
references.pmid: 15857759
references.citation: Insect Mol Biol. 2004 Feb;13(1):19-24
references.pmid: 14728663
references.citation: Insect Biochem Mol Biol. 2006 Dec;36(12):954-64
references.pmid: 17098170
references.citation: Insect Biochem Mol Biol. 2007 Dec;37(12):1249-61
references.pmid: 17967344
references.citation: J Bacteriol. 1988 Apr;170(4):1950-4
references.pmid: 3280554
references.citation: Dev Genes Evol. 2000 Jul;210(7):373-6
references.pmid: 11180843
references.citation: J Mol Biol. 1984 Sep 5;178(1):91-104
references.pmid: 6548265
references.citation: FEBS Lett. 2006 Mar 20;580(7):1846-52
references.pmid: 16513115
references.citation: J Exp Biol. 2003 Dec;206(Pt 24):4393-412
references.pmid: 14610026
references.citation: Insect Biochem Mol Biol. 2000 Dec;30(12):1213-22
references.pmid: 11044667
references.citation: Mem Inst Oswaldo Cruz. 2005 Oct;100(6):545-7
references.pmid: 16302065
references.citation: Gene. 2005 Apr 11;349:87-95
references.pmid: 15777697