Expression and persistence of a lacZ reporter gene at various stages of tilapia (Oreochromis niloticus)

Abstract

An Escherichia coli lacZ gene linked to the 4.6 kb carp ~-actin promoter/
enhancer was microinjected into the fertilised eggs of til apia COreochromis
niloticus) at a concentration of 5xl05 copies per egg. The embryos grown from
the injected eggs were homogenised at day 8 and day 14 after fertilization and
half of the homogenate was used for assaying ~-galactosidase activity by a
fluorometric method using 4-methyl-umbelliferyl ~ D Galactoside as a
substrate. DNA from the other half of the homogenate was analysed by
Southern Blotting. The incidence of expression of the trans gene was 41.6 and
25.0% for the 8-days old embryo and 14 days old fry respectively. All the
expressing individuals were positive for carrying the transgene in different
concatemeric forms. Out of eight tissues analysed from a six-month old adult
fish by X-Gal staining, only certain cells of the brain were found to be positive
for express.on of the lacZ gene although the DNA was present in all the tissues
when anal:{sed by Southern Blotting.