Roles of guanylyl cyclase system in adaptation to the environment

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We demonstrated that binding of a protein with 17 kDa, which is a medaka fish homologue of mammalian co-activator "PC4", to the nucleotides (AGACCTTTGC) between-90 and -81 in the 5'-flanking region of the OIGC6 gene are essential for transcription of the OlGC6 gene in medaka fish intestine. In European eel, it has been demonstrated that expression of the GC-C2 transcript in the intestine was increased by 100% following the transfer of yellow fresh water-acclimated eels to sea water, while no changes in expression of OlGC9 were seen when adult medaka fish individuals were transferred to 500/0 sea water. Expression of neuronal NO synthase gene (nNOS), three different subunit genes (OlGCS-α_1, OlGCS-α_2, and OlGCS-β_1) of soluble GC, and three PKG genes (PKG 1α ; PKG 1β, and PKG II) were examined during embryogenesis of medaka fish with or without morpholino antisense oligonucleotide of respective gene. nNOS and OlGCS-β_1 were expressed matemally and OlGCS-α_1, OlGCS-α_2, PKG I, and PKG II were expressed zygotically. The zygotic expression of OlGCS-α_1 was detected at stage 19, while that of OlGCS-a2 was detected at stage 16. The Hong Kong-originated medaka fish Oryzias curvinotus expresses nine genes (OcGC1-OcGC8 and OcGC-R2) for membrane GCs and three genes (OcGCS-_1 OcGCS-_2, and OcGCS-_1) for soluble GC subunits. O. curvinotus was able to produce the hybrids with O. latipes irrespective of the direction of crossing and the resulting hybrids expressed both the matemal and patemal soluble GC subunit genes almost equally, suggesting the possibility of the formation of chimeric heterodimer in the hybrids.