Showing papers by "Zhanjiang Liu published in 1999"

Development of Polymorphic EST Markers Suitable for Genetic Linkage Mapping of Catfish.

Abstract: Expressed sequence tag (EST) markers are important for gene mapping and for marker-assisted selection (MAS). To develop EST markers for use in catfish gene mapping, 100 randomly picked complementary DNAs from the channel catfish (Ictalurus punctatus) pituitary library were sequenced. The EST sequences were used to design primers to amplify channel catfish and blue catfish (I. furcatus) genomic DNAs. Polymerase chain reaction products of the ESTs were analyzed to determine length polymorphism between the channel catfish and blue catfish. Eleven polymorphic EST markers were identified. Five of the 11 EST markers were from known genes and the other six were from unidentified ESTs. Seven ESTs were found to be associated with microsatellite sequences. Analysis of channel catfish gene sequences indicated highly biased codon usage, with 16 codons being preferably used. These codons were more preferably used in highly expressed ribosomal protein genes and in highly expressed pituitary hormone genes. G/C-rich codons are less used in channel catfish than those in other vertebrates suggesting AT-richness of the channel catfish genome.

Development of Amplified Fragment Length Polymorphism (AFLP) Markers Suitable for Genetic Linkage Mapping of Catfish

Abstract: Genomic research requires many molecular markers for construction of the genetic linkage map and for marker-assisted selection (MAS). Amplified fragment length polymorphism (AFLP) markers are inherited with Mendelian expectations in catfish and, thus, are suitable for use in gene mapping and MAS. To identify large numbers of AFLP markers, 64 primer combinations were tested to generate AFLP patterns between channel catfish Ictalurus punctatus and blue catfish I. furcatus. The 64 primer combinations amplified 7,871 bands, of which 3,081 were polymorphic between the two mating parents of channel catfish and blue catfish used to produce the reference families for mapping analysis. The primer combinations that produced fewer bands showed higher rates of polymorphism. Of the 64 primers, 53 primer combinations produced clean and reproducible AFLP profiles. Nine primer combinations produced fair AFLP profiles. The remaining two primers produced poor AFLP profiles with intensive background bands. The 53 e...

Effects of Seasonal Variations, Thyroid and Steroid Hormones, and Carp Pituitary Extract on the Artificial Production of Channel Catfish Ictalurus punctatus× Blue Catfish I. furcatus Hybrids

Abstract: . The primary objective was to compare thyroid hormones and levels of carp pituitary extract for the artificial production of female Ictalurus punctatus× male I. furcatus hybrid catfish. The effects of different carp pituitary extract dosage rates (5, 6, 9, and 10 mg/kg), carp pituitary extract (6 and 10 mg/kg) supplemented with the thyroid hormones thyroxine (T4) and triiodothyronine (T3), or pregnenolone (DHP) were determined for inducing ovulation of female channel catfish, fertilization of channel catfish eggs with male blue catfish sperm, and hatching rate of these embryos. Hormone treatments thyroxine and tri-iodothyronine with carp pituitary extract, carp pituitary extract alone, and pregnenolone with carp pituitary extract used to artificially produce hybrid catfish were not different in terms of ovulation rates, eggs/kg, fry/kg body weight of female channel catfish, fertilization rates, or hatching rates (P > 0.05). These findings suggest that lower amounts of carp pituitary extract may be used to induce spawn of female channel catfish for production of channel-blue catfish hybrids and the addition of thyroid and steroid hormones is ineffective at the rates used in this study.

Characterization of nonautonomous Tc1-like transposable elements of channel catfish (Ictalurus punctatus)

Abstract: Putative nonautonomous transposable elements from channel catfish (Ictalurus punctatus) were identified. They were named Tipnon elements for Tc1-like transposable elements from channel catfish that are nonautonomous. These elements were defined by their terminal repeats that share identity to members of the known Tc1/mariner transposon superfamily. They show structural similarities to Tc1-like elements, but share little sequence identity beyond the terminal inverted repeats. They do not harbor any amino acid blocks that show similarities to the Tc1-like or other transposases and thus may represent truly nonautonomous transposons in channel catfish. They are abundant in the channel catfish genome with a copy number of 32 000, having 500 base pair per copy, this family of nonautonomous transposon-like elements account for 1.6% of the channel catfish genomic DNA. Their high abundance and transposon-like terminal repeats indicate that they may play important roles in gene evolution and in genomic architecture of catfish. Similarity search for potential coding capacity of the Tipnon elements revealed that they contain sequence blocks that can potentially encode amino acid blocks similar to the para-type sodium channel proteins in cockroaches or house flies, proteins that function in the central nervous system as voltage-gated sodium transporters. Sequences surrounding the terminal inverted repeats are divergent from those used by the reconstructed Sleeping Beauty fish transposase.