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Three guanylyl cyclases in the green shore crab, carcinus maenas: cDNA cloning and effects of molt stage on expression in molting gland (Y-organ)




Gunderson, Jennifer L., author
Mykles, Donald L., advisor
Reddy, Anireddy N., committee member
Tjalkens, Ronald B., committee member

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YO ecdysteroidogensis is suppressed by molt-inhibiting hormone (MIH) and the pleiotropic neuropeptide crustacean hyperglycemic hormone (CHH) with these neuropeptides being produced in the X-organ of the eyestalk (ES) ganglia. CHH signaling is mediated by a membrane receptor guanylyl cyclase (GC), while MIH signaling may involve a soluble NO-sensitive GC. Here we report the cloning of cDNA sequences encompassing the catalytic domain of the~ subunit of a soluble NO-sensitive GC ( Cm-GC-I ß), membrane receptor GC ( Cm-GC-II), and soluble NO-insensitive GC (Cm-GC-III) from the European green crab, Carcinus maenas, using RT-PCR and RACE. Adult C. maenas occur as two color morphs that differ in growth traits; the "green" morphs molt more frequently than the "red" morphs. These data suggest that YOs in red morphs are less active than the YOs in green morphs, and that the red morphs are refractory to molt induction by eyestalk ablation (ESA). We tested the effects of ESA on the expression of NO synthase ( Cm-NOS), Cm-GC-I ß, Cm-GC-II, and Cm-GC-III in the YOs from green and red morphs using quantitative PCR. Elongation factor-2 (Cm- EF2) served as a constitutively expressed control. ESA caused a small, transient increase in hemolymph ecdysteroid titers in both morphs, with the increase occurring at 3 days post-ESA in green morphs and at 14 days post-ESA in red morphs. ESA had no significant effect on the expression of Cm-EF2, Cm-NOS, Cm-GC-II, and Cm-GC-III, which were not correlated with hemolymph ecdysteroid titers. ESA caused a significant decrease in Cm-GC-I ß expression in red morphs, but had no significant effect in green morphs. Expression was also quantified in green morphs undergoing spontaneous natural molting. There was no significant difference in the expression of Cm-EF2, Cm-NOS, Cm- GC-II, and Cm-GC-II in YOs from intermolt, premolt, and postmolt animals. By contrast, Cm-GC-III mRNA was about 2-fold greater in YOs from postmolt animals than in intermolt and premolt animals. The results show that both color morphs are resistant to ESA and that molting has little effect on NOS and GC expression.


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Mares -- Reproduction


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