title: Loss of function of the yellow-e gene causes dehydration-induced mortality of adult Tribolium castaneum.
abstract: Yellow protein (dopachrome conversion enzyme, DCE) is involved in the melanin biosynthetic pathway that significantly accelerates pigmentation reactions in insects. Recent studies have suggested that the insect yellow genes represent a rapidly evolving gene family generating functionally diverse paralogs, but the exact physiological functions of several yellow genes are still not understood. To study the function(s) of one of the yellow genes, yellow-e (TcY-e), in the red flour beetle, Tribolium castaneum, we performed real-time PCR to analyze its developmental and tissue-specific expression, and utilized immunohistochemistry to identify the localization of the TcY-e protein in adult cuticle. Injection of double-stranded RNA for TcY-e (dsTcY-e) into late instar larvae had no effect on larval-pupal molting or pupal development. The pupal cuticle, including that lining the setae, gin traps and urogomphi, underwent normal tanning. Adult cuticle tanning including that of the head, mandibles and legs viewed through the translucent pupal cuticle was initiated on schedule (pupal days 4-5), indicating that TcY-e is not required for pupal or pharate adult cuticle pigmentation in T. castaneum. The subsequent pupal-adult molt, however, was adversely affected. Although pupal cuticle apolysis and slippage were evident, some of the adults (~25%) were unable to shed their exuvium and died entrapped in their pupal cuticle. In addition, the resulting adults rapidly became highly desiccated. Interestingly, both the failure of the pupal-adult molt and desiccation-induced mortality were prevented by maintaining the dsTcY-e-treated insects at 100% relative humidity (rh). However, when the high humidity-rescued adults were removed from 100% rh and transferred to 50% rh, they rapidly dehydrated and died, whereas untreated beetles thrived throughout development at 50% rh. We also observed that the body color of the high humidity-rescued dsTcY-e-adults was slightly darker than that of control animals. These results support the hypothesis that TcY-e has a role not only in normal body pigmentation in T. castaneum adults but also has a vital waterproofing function.
authors.affiliation: Department of Applied Biology, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Mi Young
authors.initials: MY
authors.lastname: Noh
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Manhattan, KS 66506, USA.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Kramer
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Manhattan, KS 66506, USA.
authors.forename: Subbaratnam
authors.initials: S
authors.lastname: Muthukrishnan
authors.affiliation: Department of Entomology, Kansas State University, Waters Hall, Manhattan, KS 66506, USA.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Beeman
authors.affiliation: Department of Biochemistry and Molecular Biophysics, Manhattan, KS 66506, USA.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Kanost
authors.affiliation: Department of Applied Biology, Chonnam National University, Gwangju 500-757, Republic of Korea. Electronic address: arakane@chonnam.ac.kr.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Arakane
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016000:Cluster Analysis; D003681:Dehydration / Q000201:enzymology* / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental / Q000235:genetics / Q000502:physiology*; D006813:Humidity; D007150:Immunohistochemistry; D019746:Intramolecular Oxidoreductases / Q000378:metabolism*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010858:Pigmentation / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D060888:Real-Time Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014231:Tribolium / Q000201:enzymology* / Q000254:growth & development
chemical_list: D019746:Intramolecular Oxidoreductases; C042501:dopachrome isomerase
keywords: Dehydration; Dopachrome conversion enzyme; Pigmentation; RNA interference (RNAi); Tribolium castaneum; Yellow