Changes in ecdysteroid levels and expression patterns of ecdysteroid-responsive factors and neuropeptide hormones during the embryogenesis of the blue crab, Callinectes sapidus

Aug 8, 2014General and comparative endocrinology

Changes in molting hormones and related signals during blue crab embryo development

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Abstract

Maternal levels of the ecdysone receptor and retinoid X receptor in C. sapidus ovaries are 10-50 times higher than in embryos at the yolk stage.

Ecdysteroids are known to positively control the first molt during crustacean embryogenesis.
Expression levels of maternal ecdysteroid-responsive factors suggest their potential role at the initiation of embryogenesis.
Changes in total ecdysteroids and levels of ecdysone and retinoid X receptors during embryogenesis are similar to those seen in juvenile molts.
The expression patterns of molt-inhibiting hormone and crustacean hyperglycemic hormone resemble the changes in ecdysteroid levels.
The timing of neuropeptide expression appears to be influenced by ecdysteroids.
Ecdysteroid levels during embryogenesis may correlate with the timing of Y-organ development and activity.

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Embryogenesis requires the involvement and coordination of multiple networks of various genes, according to a timeline governing development. Crustacean embryogenesis usually includes the first molt, a process that is known to be positively controlled by ecdysteroids. We determined the amounts of ecdysteroids, as well as other related factors: the ecdysone receptor (CasEcR), the retinoid X receptor (CasRXR), the molt-inhibiting hormone (CasMIH), and crustacean hyperglycemic hormone (CasCHH) during the ovarian and embryonic developments of Callinectes sapidus. In summary, the ovaries at stages 1-4 have expression levels of maternal CasEcR and CasRXR 10-50 times higher than levels seen in embryos at the yolk stage. This large difference in the amount of the these factors in C. sapidus ovaries suggests that these maternal ecdysteroid-responsive factors may be utilized at the initiation of embryogenesis. During embryogenesis, the changes in total ecdysteroids and levels of CasEcR and CasRXR expression are similar to those observed in juvenile molts. The full-length cDNA sequence of the C. sapidus BTB domain protein (CasBTBDP) initially isolated from Y-organ cDNA, contains only Broad-Complex, Tramtrack, and Bric a brac (BTB) domains. The levels of CasBTBDP are kept constant throughout embryogenesis. The expression profiles of CasMIH and CasCHH are similar to the titers of ecdysteroids. However, the timing of their appearance is followed by increases in CasEcRs and CasRXRs, implying that the expressions of these neuropeptides may be influenced by ecdysteroids. Moreover, the ecdysteroid profile during embryogenesis may track directly with the timing of organogenesis of Y-organs and their activity. Our work reports, for first time, the observed expression and changes of ecdysteroid-responsive factors, along with CasCHH and CasMIH, during embryogenesis in the crustacean C. sapidus.

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Changes in ecdysteroid levels and expression patterns of ecdysteroid-responsive factors and neuropeptide hormones during the embryogenesis of the blue crab, Callinectes sapidus

Abstract

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