Proteomic analysis of a toxic dinoflagellate Alexandrium catenella under different growth phases and conditions

Alexandrium is a widely spread dinoflagellate genus throughout many regions of the world, which not only causes the harmful algal blooms (HABs) but also results in the paralytic shellfish poisoning (PSP) throughout the world. This study compared protein profiles of A. catenella grown under different growth phases and conditions using a proteomic approach, and identified the differentially expressed proteins. The results showed that the expressions of proteins identified in three different regions of the gels, the groups 1, 2 and 3 proteins, varied significantly with the growth phases and conditions. Group 1 proteins and six Group 2 proteins were highly expressed at the initial, exponential and stationary growth phases, eight Group 2 proteins were highly expressed only at the initial phase, and Group 3 proteins were highly expressed at the exponential and/or stationary phases. However, all these proteins were expressed at low levels or were barely visible at the dissipation phase. The expressions of groups 1 and 2 proteins were low or barely visible in various growth conditions except in continuous darkness they were highly expressed. Group 3 proteins, on the other hand, were overexpressed in continuous illumination and expressed at low levels or barely visible in continuous darkness or under nitrate-starvation. The data from MALDI-TOF-TOF mass spectrometry demonstrated that these differentially expressed proteins were associated with macromolecular biosynthesis, photosynthesis, tRNA synthesis and DNA stability, stress response and cell division regulation. Synthetase was the major component of the altered proteins. This is one of the first comprehensive proteomic study of a dinoflagellate, A. catenella, that provides a fundamental understanding of the proteins involved in A. catenella growth and response to environmental stresses, and potential physiological indicator proteins related to growth and environmental stress have been identified.