NanoLC-MS/MS DDA Chroococcidiopsis thermalis PCC 7203 thylkoids WL vs. FRL

Chroococcidiopsis thermalis is an extremophilic cyanobacterium that is adaptable to a widerange of environments including deserts, where it can maintain viability after desiccation. This species is also capable of photoautotrophic growth under far-red light (FRL, 750 nm) The proteomic comparison in this study, in conjunction with topographical imaging of thylakoid membranes by atomic force microscopy, supports earlier findings that FRL growth is accompanied by the synthesis of alternative photosynthesis-related proteins. Under white light (WL), a number of phycobilisome (PBS) and photosystem (PS) subunits were predominant at levels 2 - 14-fold greater compared to FRL growth. Two antenna family proteins were markedly more abundant under WL, with a fold-difference of approximately 80. While WL-associated proteins persisted at relatively low abundance under FRL, an exclusive set of PBS and PS subunit isoforms was expressed under FRL. These proteins were undetectable under WL, in many cases encoded in a discrete FRL-associated gene cluster. In line with the expected higher energy capture rate under WL, complexes associated with electron transport (eg. cytochrome b6f) and the ATP synthase were 1.2 – 3.4 times more abundant than under FRL.