Amino Acid Incorporation in Developing Fucus Embryos

Abstract

The incorporation of 14C-leucine and 14C-amino acid mixture into protein in unfertilized eggs and developing embryos of the brown alga Fucus vesiculosus L. was studied. Bacterial contamination was initially a problem, but it was found that the addition of 40 [mu]g/ml chloramphenicol to the incubation medium would inhibit bacterial protein synthesis without affecting early development of the Fucus embryos. The kinetics of uptake and incorporation of 14C-leucine into the trichloroacetic acid-soluble and -inosluble fractions indicated that the exogenous precursor did not equilibrate with the main soluble leucine pool before incorporation into protein. Uptake and incorporation of leucine by embryos 90 to 175 min. old were proportional to exogenous leucine concentration over the range 5 x 10-6 M to 5 x 10-3 M. Unfertilized eggs will incorporate 14C-leucine into protein. The rate of this incorporation increases dramatically in newly fertilized eggs with a maximum rate at 3.5 hr., a period of cell wall formation and increasing metabolic rates. Thereafter, the rate *of incorporation declines until approximately 15-17 hr. when it increases again concurrently with the onset of rhizoid initiation and cell division.