Expression of aldolase-controlling genes in hybrid fish embryos. Use of thermostability as a genetic marker.

A new method based on differences in protein thermostability has been proposed for studying genetic control of protein synthesis during development. The effectiveness of this method was checked for aldolase, whose thermostability was established from the temperature required for 50% inactivation after heating for 30 min (T50%). Eggs from a relatively cryophilic species, the loach, were fertilized with sperm from warm-water aquarium fish: the danio, barb, rasbora, and goldfish. The T50% for aldolase from the hybrid embryos and fry was 1-4 degrees higher than for aldolase from the loach. The increase in T50% in the loach times danio and loach times rasbora hybrids was shown to be caused by functioning of the paternal aldolase-controlling genes, which began at the somite-formation stage and coincided with the increase in enzyme activity in the embryo. The value of T50% was increased to a greater extent and reached its maximum more rapidly in the somite tissues than in the cephalic tissues. A decrease in aldolase thermostability occurred in reciprocal danio times loach hybrids during the same developmental stages.