Variations in the expression of photosynthesis-related proteins in field Chattonella marina cells during a harmful algal bloom

Time series variations in protein expression profiles in field Chattonella marina cells were investigated during a HAB occurred in the inner part of Ariake Sea, Japan (5-14 September, 2012). This study aimed to gather information on the molecular mechanisms underlying the physiological responses in field C. marina population during HAB. Proteomic analysis showed that the abundance of -37% protein spots (40 out of 108 detected from 2-DE gel images) significantly varied with the sampling date. Significant decreases in the abundances of proteins involved in photosystem II (LHCP 4), electron transfer chain (Cyt c553), Calvin cycle (GAPDH), and chloroplast antioxidant system (2-Cys Prx) were observed as the bloom progressed, suggesting the efficiencies of those photosynthetic pathways declined during the bloom. In addition, the abundances of the above proteins showed significant positive correlations with the F_v/F_m ratio and growth rate of C. marina and with DIN concentrations (except LHCP 4). Our findings suggested that declined expressions of those photosynthesis-related proteins presented some molecular foundation of the decreases in F_v/F_m ratio and growth rate of C. marina during the bloom, and also provided insight into mechanistic links between the external/internal factors and physiological responses of C. marina that may ultimately dictate the ecology of the bloom.