title: Suppression of Laccase 2 severely impairs cuticle tanning and pathogen resistance during the pupal metamorphosis of Anopheles sinensis (Diptera: Culicidae).
abstract: BACKGROUND
  Phenol oxidases (POs) catalyze the oxidation of dopa and dopamine to melanin, which is crucial for cuticle formation and innate immune maintenance in insects. Although, Laccase 2, a member of the PO family, has been reported to be a requirement for melanin-mediated cuticle tanning in the development stages of some insects, whether it participates in cuticle construction and other physiological processes during the metamorphosis of mosquito pupae is unclear.
  
  
  METHODS
  The association between the phenotype and the expression profile of Anopheles sinensis Laccase 2 (AsLac2) was assessed from pupation to adult eclosion. Individuals showing an expression deficiency of AsLac2 that was produced by RNAi and their phenotypic defects and physiological characterizations were compared in detail with the controls.
  
  
  RESULTS
  During the dominant expression period, knockdown of AsLac2 in pupae caused the cuticle to be unpigmented, and produced thin and very soft cuticles, which further impeded the eclosion rate of adults as well as their fitness. Moreover, melanization immune responses in the pupae were sharply decreased, leading to poor resistance to microorganism infection. Both the high conservation among Laccase 2 homologs and a very similar genomic synteny of the neighborhood in Anopheles genus implies a conservative function in the pupal stage.
  
  
  CONCLUSIONS
  To our knowledge, this is the first study to report the serious phenotypic defects in mosquito pupae caused by the dysfunction of Laccase 2. Our findings strongly suggest that Laccase 2 is crucial for Anopheles cuticle construction and melanization immune responses to pathogen infections during pupal metamorphosis. This irreplaceability provides valuable information on the application of Lacccase 2 and/or other key genes in the melanin metabolism pathway for developing mosquito control strategies.
authors.affiliation: Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China.
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Du
authors.affiliation: Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China.
authors.forename: Zheng-Wen
authors.initials: ZW
authors.lastname: Yan
authors.affiliation: Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China.
authors.forename: You-Jin
authors.initials: YJ
authors.lastname: Hao
authors.affiliation: Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China.
authors.forename: Zhen-Tian
authors.initials: ZT
authors.lastname: Yan
authors.affiliation: Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China.
authors.forename: Feng-Ling
authors.initials: FL
authors.lastname: Si
authors.affiliation: Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China. bin.chen@cqnu.edu.cn.
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.affiliation: Chongqing Key Laboratory of Vector Insects; Institute of Entomology and Molecular Biology; College of Life Sciences, Chongqing Normal University, Chongqing, 401331, China. qiaoliangswu@163.com.
authors.forename: Liang
authors.initials: L
authors.lastname: Qiao
mesh_terms: D000818:Animals; D000852:Anopheles / Q000201:enzymology* / Q000276:immunology*; D060467:Disease Resistance; D020869:Gene Expression Profiling; D020868:Gene Silencing; D034582:Integumentary System / Q000502:physiology*; D042845:Laccase / Q000172:deficiency*; D011679:Pupa / Q000201:enzymology / Q000276:immunology; D034622:RNA Interference; D017422:Sequence Analysis, DNA; D013633:Tanning
chemical_list: D042845:Laccase
keywords: Anopheles sinensis; Cuticle tanning; Immunity; Laccase 2; Melanization; Phenol oxidases; Pupal metamorphosis