Abstract: Porella glacialis was discovered from the Antarctic land-fast sea ice and Arctic water column. Recently, P. glacialis-like genotypes were found in temperate waters. The dinoflagellate Rubisco and PCNA antibodies detected specific bands of ~53kDa and ~55kDa in P. glacialis. As shown by the gradient temperature experiment, the diel expression of Rubisco protein maintained nearly stable in the 4℃ culture. The diel expression of PCNA closely related with the %S peak. P. glacialis continued to grow after the cell density increased to 1.1×105cells.ml^-1. When the temperature rose up to 15 and 20℃, the dinoflagellate was stressed with fast reducing cell density, altered cell cycle, inactive cell division or even stopped, and greatly reduced abundances and altered diel expression patterns of Rubisco and PCNA. The culture was stressed by 20℃ more. However, the cell density of P. glacialis did not quickly decrease when moved to 15℃. And the cell cycle pattern and the reserved expressing rhythm of the indicative proteins indicated possible cell division of a small part of cells. We concluded that as a polar dinoflagellate, P. glacialis might exist for a long time in the relatively long and gradual process of warming in the polar region. And it was not surprised for the presence of the P. glacialis-like genotypes in temperate waters.

Key words: Polarella glacialis, cell cycle, Rubisco, PCNA