Molecular Cloning and Antiserum Development of Cyclin Box in the Brown Tide Alga Aureococcus anophagefferens

Cyclins can be useful cell cycle markers for growth rate studies on harmful algal blooms. In this study, a gene fragment corresponding to cyclin box was cloned for the brown tide alga Aureococcus anophagefferens. This algal gene fragment, designated as Btcycl1, was most similar to cyclin B. Oligopeptides based on the deduced amino acid sequence were synthesized and used to raise an antiserum that reacted on Western blots with a protein of about 63 kDa, the same size as cyclin B in other organisms. The cyclin B–like protein recognized by this antiserum, and the messenger RNA amplified using the primers, were more abundant in exponential cultures and decreased markedly in stationary cultures. This protein also appeared to be cell cycle dependent. Immunofluorescence labeling showed that this antiserum specifically stained a protein in Aureococcus cells and had no cross-reaction with bacteria that were present in the algal culture. The Btcycl1 sequence and the antiserum will provide a useful tool for studies on regulation of in situ growth rate for this brown tide alga. Received May 22, 2000; accepted July 13, 2000.