Abstract
In order to better understand the consequences of Fe stress for algal photosynthesis and the cell division cycle, Dunaliella tertiolecta was grown in batch cultures under high and low Fe (−Fe) conditions, and several physiological, cytological, and biochemical parameters were measured. Results showed characteristics typical of iron stress in the −Fe cultures, viz. chlorosis and marked reduction in photochemical efficiency. The maximal proliferating nuclear antigen (PCNA) index (fPCNA: the percentage of cells containing proliferating cell nuclear antigen), cell division rate, and cell size were all slightly but significantly reduced under iron stress. In contrast, the total cellular content of Rubisco and the light harvesting protein complex, the cellular localization of PCNA, and the duration of the PCNA-containing phase of the cell cycle all appeared to be unaffected by Fe stress. More strikingly, Fe stress disrupted the diel pattern of the PR index (the percentage of cells containing distinct pyrenoid-Rubisco units) that is typically observed for nutrient replete cultures. Although growth rates of Fe-stressed cultures decreased as a consequence of reduced fPCNA maxima, the accuracy of the PCNA method for estimating growth rate did not seem to be affected by iron stress. Upon addition of iron-replete medium, the typical diel pattern of the PR index was restored and physiological damage imposed by Fe stress was repaired within 24 h. The results suggest that (1) iron stress reversibly impairs the mechanism by which cells under iron-replete condition respond to light–dark variation through relocating Rubisco between the pyrenoid and the stroma and (2) the effects of iron stress on the cell cycle probably do not affect the relationship between the growth rate of this phytoplankter and fPCNA and thus will probably allow the use of the PCNA method for in situ growth rate estimation in iron-limiting areas of the world's oceans.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
