Expression of RXR, EcR, E75 and VtG mRNA levels in the hepatopancreas and ovary of the freshwater edible crab, Oziothelphusa senex senex (Fabricius, 1798) during different vitellogenic stages

Apr 4, 2015Die Naturwissenschaften

Levels of RXR, EcR, E75, and VtG gene activity in the liver-like organ and ovaries of the freshwater edible crab during egg development stages

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Abstract

Expression levels of retinoid X receptor (RXR), ecdysone receptor (EcR), and ecdysone inducible gene (E75) vary significantly during vitellogenesis in female Oziothelphusa senex senex.

RXR and EcR levels significantly increased in the ovaries during vitellogenic stage I.
E75, EcR, and vitellogenin (VtG) levels in the hepatopancreas significantly elevated during vitellogenic stages I and II.
RXR levels in the hepatopancreas increased only during vitellogenic stage I.
During vitellogenic stage III, RXR, EcR, and VtG levels in the hepatopancreas significantly decreased.
VtG was present in haemolymph, hepatopancreas, and ovary extracts from females, but absent in males.
RXR, EcR, and E75 may regulate VtG synthesis in the hepatopancreas and uptake in the ovary.

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The objective of the present study was to investigate the expression profile of retinoid X receptor (RXR), ecdysone receptor (EcR) and ecdysone inducible gene (E75) in the hepatopancreas and ovary of Oziothelphusa senex senex during different vitellogenic stages. RXR, EcR and E75 complementary DNAs (cDNAs) were isolated from the ovaries, while vitellogenin (VtG) cDNA was isolated from the hepatopancreas of vitellogenic female crab. Deduced amino acid sequence of the messenger RNAs (mRNAs) of RXR, EcR and E75 showed more than 80% identity with their respective mRNAs of other brachyurans. VtG mRNA was not detected in the ovary throughout vitellogenic stages. RXR and EcR were significantly increased in the ovaries during vitellogenic stage I. The levels of EcR, E75 and VtG in the hepatopancreas elevated significantly during vitellogenic stages I and II, whereas the levels of RXR elevated only in vitellogenic stage I. During vitellogenic stage III, the levels of RXR, EcR and VtG in the hepatopancreas were significantly decreased. Immunoprecipitation analysis revealed the presence of VtG in the haemolymph, hepatopancreas and ovary extracts from the females but absent in haemolymph and hepatopancreas extract of males. It can be inferred that RXR, EcR and E75 are involved in the regulation of synthesis of VtG in hepatopancreas, whereas in ovary, it is hypothesized that they play an important role in the uptake of VtG from the haemolymph, probably by regulating the levels of vitellogenin receptor. These are the first data showing an association between the expression levels of RXR, EcR and E75 and vitellogenesis and provide an alternative molecular intervention mechanism to the traditional eyestalk ablation to induce vitellogenesis and ovarian maturation in crustaceans.

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Expression of RXR, EcR, E75 and VtG mRNA levels in the hepatopancreas and ovary of the freshwater edible crab, Oziothelphusa senex senex (Fabricius, 1798) during different vitellogenic stages

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