Chen, Y. Rensselaer Polytechnic Institute, cheny6@rpi.edu
Dominic, B. Rensselaer Polytechnic Institute, dominb@rpi.edu
Zehr, J. P. Rensselaer Polytechnic Institute, zehrj@rpi.edu

 
CIRCADIAN CONTROL OF THE PHOTOSYNTHETIC APPARATUS IN THE NITROGEN FIXING CYANOBACTERIUM TRICHODESMIUM
 
Trichodesmium spp. are marine nonheterocystous cyanobacteria which fix nitrogen aerobically during the day, and are important in oceanic carbon and nitrogen cycling in subtropical and tropical waters. We have recently shown that the nitrogen fixation apparatus is regulated through a circadian rhythm. Little is known about how photosynthesis is regulated in relation to the nitrogen fixation apparatus. We found that the photosynthetic apparatus is also under circadian control, although offset from the cycle of nitrogenase (nif) transcription. Furthermore, transcription of genes for PSII (psbA) are offset from that of PSI (psaA). Thus, the transcripts of psbA, psaA, and nifHDK are cyclic, but offset in phase, with nif transcription initiated prior to the light period, followed by psbA and finally psaA transcription. Interestingly, psaA transcription peaks near the end of the light period. Short-term increases in light intensity enhances psbA transcription and nitrogenase activity, but does not affect psaA or nifHDK transcript levels. The results indicate that there are striking differences in the patterns of nitrogenase and photosynthesis gene regulation. The different patterns of gene transcription in relation to light may have implications for photosynthesis and nitrogen fixation during vertical movement through the water column.
 
Day: Thursday, Feb. 4
Time: Poster
Location: Sweeney Center
 
Code: CS62TH0527S