Amino Acid Incorporation in Developing Fucus Embryos

The incorporation of (14)C-leucine and (14)C-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 mug/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 (14)C-leucine into the trichloroacetic acid-soluble and -insoluble 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 minutes 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 (14)C-leucine into protein. The rate of this incorporation increases dramatically in newly fertilized eggs with a maximum rate at 3.5 hours, a period of cell wall formation and increasing metabolic rates. Thereafter, the rate of incorporation declines until approximately 15 to 17 hours when it increases again concurrently with the onset of rhizoid initiation and cell division.