Meeting Abstract

P3.132  Jan. 6  Salinity-related mRNA expression of Crustacean Hyperglycemic Hormone isoforms in the euryhaline crab Pachygrapsus marmoratus SPANINGS-PIERROT, C.*; TOULLEC, J.-Y.; SERRANO, L.; TOWLE, D.W.; Univ. Montpellier II, France; UPMC Paris, France; Auburn Univ., AL; MDIBL, ME, USA celine.spanings-pierrot@univ-montp2.fr

Two CHH isoforms were characterized in neuroendocrine organs of the crab Pachygrapsus marmoratus, one form more specific of the X-organ/sinus gland complex (SG-CHH) and the second one mainly expressed in the pericardial organs (PO-CHH). Both complete cDNAs were sequenced. The preprohormones are composed of identical sequences for the signal peptide, the crustacean hyperglycemic hormone precursor and the first 40 amino acids in the N-terminal region. A splicing event in the SG-CHH mRNA results in different C-terminal sequences. Both isoforms are present in the XO/SG complex while only the unspliced form has been found in the PO. The potential regulatory role of CHH with respect to osmotic and ionic regulation in crustaceans prompted us to examine whether CHH mRNA expression might change with salinity acclimation. Real-time quantitative PCR results indicated a 2.5-fold and a 7-fold increase in PO-CHH expression 4 h and 6 h after transfer to low salinity respectively. Two days after transfer, the level returned to the base line value. CHH abundance in hemolymph is known to vary according to a daily cycle but mRNA expression of the CHH unspliced form (PO-CHH) was relatively stable during a circadian cycle in seawater. On the other hand, SG-CHH mRNA expression increased 2 h and 4 h after transfer in diluted seawater, but it exhibited a similar daily variation in crabs maintained in seawater which even continued to increase at 6 h. These results support the hypothesis of the involvement of the CHH unspliced isoform in short-term adaptation to osmotic stress while the other isoform seems mostly implicated in glycemia regulation. Supported by NSF IBN-0340622 and MDIBL NIA