Proliferating cell nuclear antigen (PCNA) as a marker of cell proliferation in the marine dinoflagellate Prorocentrum donghaiense Lu and the green alga Dunaliella salina Teodoresco

Proliferating cell nuclear antigen (PCNA) was detected in Prorocentrum donghaiense Lu and Dunaliella salina Teodoresco by enhanced chemiluminescence techniques with one mono-antibody. The observed band detected on western blots of P. donghaiense and D. salina had a molecular weight of 36-33 kDa rather than a PCNA-like protein with a size of 55 kDa reported in the dinoflagellates Crypthecodinium cohnii Biecheler and Gymnodinium catenatum Brav. The abundance of PCNA proteins was growth-stage dependent. Whole-cell immunoflurescence labeling showed that the PCNA antibody specifically stained the target proteins in P. donghaiense and D. salina, and PCNA is only present in the nucleus during the cell cycle. Synchronized cells of P. donghaiense show a cell cycle specific expression pattern with the highest expression in S phase and little expression in the G(1) and G(2)/M phases. The results demonstrated that the PCNA-like proteins could be a marker for the estimation of marine phytoplankton growth rates. The different sizes of the PCNA-like proteins observed in dinoflagellates could be related to the variety of dinoflagellate chromosomal structure.