Functional Roles of Hypertrehalosemic Hormone Related to Reproduction and Antioxidative Stress Responses in the German cockroach Blattella germanica (L.)
Date Issued
2011
Date
2011
Author(s)
Huang, Jia-Hsin
Abstract
A hypertrehalosemic hormone (HTH) peptide has been identified in the adipokinetic hormone (AKH) family to induce mobilization of carbohydrate in many insects. The aim of this study was to investigate the functions of hypertrehalosemic hormone in relation to reproduction and antioxidative stress response in the German cockroach Blattella germanica. I have isolated the Blage-HTH and its receptor (Blage-HTHR) genes, and thus studied their function through RNA interference (RNAi) to knockdown their expressions. The conventional role of HTH mediating trehalose homeostasis was observed in both sexes, in which the hemolymph trehalose was significantly reduced by RNAi-mediated knockdown of either Blage-HTH or Blage-HTHR genes. Especially, Blage-HTH regulated the increase of hemolymph trehalose in parallel with the ovarian development in the virgin females. Furthermore, Blage-HTH would assist the oviposition process because the ootheca production was delayed in the virgin females with either Blage-HTH or Blage-HTHR silenced.
In addition, I have unveiled another function of Blage-HTH against oxidative stress in B. germanica. Paraquat (PQ), a bipyridilium herbicide used in this study to elicit oxidative stress, causes a detrimental effect on the lifespan of 10-day-old adult males. Co-injection of synthetic HTH peptides at 10, 40, and 80 pmol concentrations significantly reduced the speed of mortality increase, with median survival time attained about 7 days in contrast to 4 days without HTH injection. However, PQ treatment caused a rapid mortality increase, with median survival time attained on 2 days, in the male adults whose Blage-HTH and Blage-HTHR were silenced simultaneously. I further examined the lipid peroxidation as an indicator of oxidative stress in the hemolymph after PQ treatment. Results showed that co-injeciton of HTH peptide maintained a normal level of lipid peroxidation, but it was not rescued by HTH in Blage-HTH and Blage-HTHR knockdown specimens. Finally, Blage-HTH also stimulated the expression of COXI (cytochrome c oxidase subunit I) and CYP4G19 (cytochrome P4504G19) in the fat body under oxidative stress elicited by PQ. The mechanism how Blage-HTH potentiates antioxidant protection has been discussed in the present study.
Subjects
Adipokinetic hormone
Trehalose
Oviposition
Oxidative stress
Hypertrehalosemic hormone receptor
RNA interference
Paraquat
Type
thesis
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