Changes in mRNA expression of grouper (Epinephelus coioides) growth hormone and insulin-like growth factor I in response to nutritional status.
Growth hormone (GH) and insulin-like growth factor-I (IGF-I) are key links to nutritional condition and growth regulation in teleost. To understand the endocrine mechanism of growth regulation in grouper, we cloned the cDNAs for grouper GH and IGF-I and examined their mRNA expression during different nutritional status. Grouper GH cDNA is 936 base pairs (bp) long excluding the poly-A tail. It contained untranslated regions of 85 and 231bp in the 5'- and 3'-ends, respectively. It has an open reading frame of 612bp coding for a signal peptide of 17 amino acids (aa) and a mature hormone of 187aa residues. Based on the aa sequence of the mature hormone, grouper GH shows higher sequence identity (>76%) to GHs of perciforms than to GHs of cyprinids and salmonids (53-69%). Grouper preproIGF-I cDNA consisted of 558bp, which codes for 186aa. This is composed of 44aa for the signal peptide, 68aa for the mature peptide comprising B, C, A, and D domains, and 74aa for the E domain. Mature grouper IGF-I shows very high sequence identity to IGF-I of teleost fishes (84-97%) compared to advanced groups of vertebrates such as chicken, pig, and human (80%). Using DNA primers specific for grouper GH and IGF-I, the changes in mRNA levels of pituitary GH and hepatic IGF-I in response to starvation and refeeding were examined by a semi-quantitative RT-PCR. Significant elevation of GH mRNA level was observed after 2 weeks of food deprivation, and increased further after 3 and 4 weeks of starvation. GH mRNA level in fed-controls did not change significantly during the same period. Hepatic IGF-I mRNA level decreased significantly starting after 1 week of starvation until the 4th week. There was no significant change in IGF-I mRNA levels in fed-controls. One week of refeeding can restore the GH and IGF-I mRNA back to its normal levels. Deprivation of food for 1-4 weeks also resulted in cessation of growth and decrease in condition factor.
Pedroso
Fiona L
FL
Aquaculture Department, Southeast Asian Fisheries Development Center (SEAFDEC AQD), Tigbauan 5021, Iloilo, Philippines. fiona_pedroso@lycos.com
de Jesus-Ayson
Evelyn Grace T
EG
Cortado
Hanna H
HH
Hyodo
Susumu
S
Ayson
Felix G
FG
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001492:Bass / Q000235:genetics* / Q000502:physiology; D049628:Body Size / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D005247:Feeding Behavior / Q000502:physiology*; D029941:Fish Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D013006:Growth Hormone / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013217:Starvation / Q000503:physiopathology
D018076:DNA, Complementary; D029941:Fish Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone