ORIGINAL ARTICLE Synechocystis mutants defective in manganese uptake regulatory system, ManSR, are hypersensitive to strong light Anna Zorina 1 • Maria A. Sinetova 1 • Elena V. Kupriyanova 1 • Kirill S. Mironov 1 • Irina Molkova 1 • Lyudmila V. Nazarenko 2 • Vladislav V. Zinchenko 3 • Dmitry A. Los 1 Received: 10 November 2015 / Accepted: 18 December 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract High affinity transport of manganese ions (Mn 2? ) in cyanobacteria is carried by an ABC-type transporter, encoded by the mntCAB operon, which is derepressed by the deficiency of Mn 2? . Transcription of this operon is negatively regulated by the two-component system consisting of a sen- sory histidine kinase ManS and DNA-binding response reg- ulator ManR. In this study, we examined two Synechocystis mutants, defective in ManS and ManR. These mutants were unable to grow on high concentrations of manganese. Fur- thermore, they were sensitive to high light intensity and unable to recover after short-term photoinhibition. Under standard illumination and Mn 2? concentration, mutant cells revealed the elevated levels of transcripts of genes involved in the formation of Photosystem II (psbA, psbD, psbC, pap- operon). This finding suggests that, in mutant cells, the PSII is sensitive to high concentrations of Mn 2? even at relatively low light intensity. Keywords Synechocystis Á Cyanobacteria Á Ions Á Manganese Á Sensors Á Stress Á Transcription factor Á Transporter Abbreviations Hik Histidine kinase Rre Response regulator ORF Open reading frame PS II Photosystem II RC Reaction center Introduction Manganese (Mn 2? ) is a cofactor for many enzymes such as Mn-dependent superoxide dismutase, catalase, Mn-depen- dent pyruvate carboxylase, phosphoenolpyruvate carboxy- lase, and some other enzymes (Larson and Pecoraro 1992). Four Mn 2? atoms form a Mn 4 CaO 5 cluster of oxygen evolving complex of the photosystem II (PSII) (Umeno et al. 2011). Manganese plays an important role in regulation and protec- tion of the photosynthetic apparatus from the effects of various stressors, such as strong UV radiation or high temperatures (Hou and Hou 2013). Thus, Mn 2? transport in photoau- totrophic organisms is, in fact, an important stage of cellular regulatory events—from the operation of PSII to changes in the activity of Mn-dependent enzymes. Cyanobacteria serve as a convenient model for studying the molecular mechanisms of functioning of the photo- synthetic apparatus. Mn 2? ions enter into the cells of cyanobacteria through the ABC-type transporter (Davidson et al. 2008), which is encoded by the mntCAB operon (Bartsevich and Pakrasi 1995). In sea or fresh water with low Mn 2? content, the cyanobacterial operon mntCAB is active. It produces three transmembrane transporter pro- teins that pump Mn 2? into cells (Bartsevich and Pakrasi 1996). Cells of the cyanobacterium Synechocystis sp. strain PCC 6803 (hereafter, Synechocystis) determine the Mn 2? Guest Editor: Suleyman Allakhverdiev. & Dmitry A. Los losda@ippras.ru 1 Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya Street 35, Moscow, Russia 127276 2 Moscow City Teacher Training University, 2nd Agricultural Passage 4, Moscow, Russia 129226 3 Department of Genetics, Faculty of Biology, Moscow State University, Moscow, Russia 123 Photosynth Res DOI 10.1007/s11120-015-0214-x