ORIGINAL ARTICLE Iron deficiency cause changes in photochemistry, thylakoid organization, and accumulation of photosystem II proteins in Chlamydomonas reinhardtii Elsin Raju Devadasu 1 • Sai Kiran Madireddi 1 • Srilatha Nama 1 • Rajagopal Subramanyam 1 Received: 25 January 2016 / Accepted: 13 June 2016 / Published online: 21 June 2016 Ó Springer Science+Business Media Dordrecht 2016 Abstract A trace element, iron (Fe) plays a pivotal role in photosynthesis process which in turn mediates the plant growth and productivity. Here, we have focused majorly on the photochemistry of photosystem (PS) II, abundance of proteins, and organization of supercomplexes of thylakoids from Fe-depleted cells in Chlamydomonas reinhardtii. Confocal pictures show that the cell’s size has been reduced and formed rosette-shaped palmelloids; however, there is no cell death. Further, the PSII photochemistry was reduced remarkably. Further, the photosynthetic efficiency analyzer data revealed that both donor and acceptor side of PSII were equally damaged. Additionally, the room-tem- perature emission spectra showed the fluorescence emis- sion maxima increased due to impaired energy transfer from PSII to PSI. Furthermore, the protein data reveal that most of the proteins of reaction center and light-harvesting antenna were reduced in Fe-depleted cells. Additionally, the supercomplexes of PSI and PSII were destabilized from thylakoids under Fe-deficient condition showing that Fe is an important element in photosynthesis mechanism. Keywords Blue native gel electrophoresis Á Fe deficiency Á Light-harvesting complexes Á Photochemistry Á Photosystem II Á Thylakoid organization Introduction Iron is a relatively abundant micronutrient in the earth’s crust, which often chronically limits to photosynthesis in the ocean and on land also. Iron is present predominantly in the poor form of insoluble complexes, such as Fe(III) ferric oxides in oxygen-rich surface water and neutral to alkaline soil. The soluble form of Fe(II) is very limited in soil, and the low bioavailability of iron complexes creates a major obstacle for photosynthetic organisms (Glaesener et al. 2013). Fe deficiency in photosynthetic organisms is evident by the development of chlorosis (loss of chlorophyll), which is accompanied by loss of photosynthetic machinery and inhibition of photosynthetic electron transport reac- tions (Spiller and Terry 1980). It is well known that Fe is a cofactor in photosystem (PS) II, PSI, the cytochrome (Cyt) b6/f complex, and Cyt c6 (Yadavalli et al. 2011, 2012a). Since PSI is the prime target because of its relatively high Fe content (12 Fe per PSI) and for instance, changes from 4:1 ratio of PSI:PSII to 1:1 under Fe deficiency in cyanobacteria (Straus 2004). Further, Fe deficiency causes a decrease in the number of PSI complex, resulting in a bottleneck in the photosynthetic electron flow (Strzepek and Harrison 2004). Most of the cyanobacteria species express the auxiliary light-harvesting proteins which increase the cross section of PSI to balance a similar level of electron throughput with a smaller Fe investment to avoid the oxidative stress in the cell (Chau- han et al. 2011). In cyanobacteria, the alteration in the pigment–protein complex and appearance of an additional pigment–protein complex around PSII (IdiA: Iron defi- ciency induced protein) protect PSII at the acceptor side against damage (Michel et al. 1996; Michel and Pistorius 2004) and formation of an iron stress-induced protein A (IsiA) (Boekema et al. 2001; Chauhan et al. 2011). Fe Electronic supplementary material The online version of this article (doi:10.1007/s11120-016-0284-4) contains supplementary material, which is available to authorized users. & Rajagopal Subramanyam srgsl@uohyd.ernet.in 1 Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad 500046, India 123 Photosynth Res (2016) 130:469–478 DOI 10.1007/s11120-016-0284-4