Research - Institute of Plant Biology - Laboratory of Molecular Stress an Photobiology

scientific adviser

Péter KÓS senior research associate
István Zoltán VASS research associate
Ateeq-ur REHMAN research associate
László SASS scientific administrator
Ivy MILLACK postdoctoral researcher
Sandeesha KODRU Ph.D. student
Gábor PATYI Ph.D. student
Gabriella FLEIT laboratory assistant
Györgyi MÁNDITY laboratory assistant


Environmental factors which impose adverse effects on photosynthetic organisms include light, drought, heavy metals and oxidative agents. By using a multidisciplinary approach, we investigate the mechanisms by which abiotic stress factors and inducers of reactive oxygen species damage plants and cyanobacteria. We also study the defense and acclimation responses which are induced by these stimuli.

Electron transport in the Photosystem II complex of photosynthesis

Photosystem II (PSII) of the photosynthetic apparatus is a multisubunit pigment-protein complex in the thylakoid membrane, which performs light-induced oxidation of water and reduction of plastoquinone. We study the mechanisms of electron transport in PSII by chlorophyll fluorescence and other biophysical methods in combination with mathematical modeling approaches.


Light is not only the basic driving force of photosynthesis, but also an important damaging factor of the photosynthetic apparatus. We have developed a model of photodamage and photoprotection of the Photosystem II (PSII) complex in which charge recombination processes play a dual role by participating both in damaging reactions via 3P680 sensitized singlet oxygen formation, as well as in photoprotection via non-radiative dissipation of 3P680 precursors. Predictions of this model have been experimentally verified by modeling of PSII electron transport reactions, and 1O2 detection in intact cyanobacterial cells.

Singlet oxygen detection

TOur group has played a leading role in developing methods for detection of various reactive oxygen species in plant systems in the last 20 years. However, there were no methods available for 1O2 detection which could be applied in intact algal or cyanobacterial cells due to the inability of known 1O2 traps to penetrate through the cell wall. We achieved a breakthrough in this field by developing a His-mediated 1O2 trapping method, which was successfully applied in Syncehocystis cells and opened the way for several applications which require 1O2 detection.

Alternative electron transport routes

Besides the well studied linear and cyclic pathways of photosynthetic electron transport recent studies have reveled important alternative routes. One of them is mediated by flavodiiron proteins. We have shown in cooperation with Prof. Aro (Turku) that the Flv2/Flv4 proteins transfer electrons from PSII or from the PQ pool to stromal components in the cyanobacterium Synechocystis 6803 via a novel pathway, which provides protection against 1O2 mediated photodamage by decreasing the reduction level of the PQ pool. In another approach we have shown that Synechocystis 6803 has an active sulfide-plastoquinine oxidoreductase enzyme, which transfers electrons from sulfide compounds to the PQ pool of the thylakoid membrane and represents an alternative electron transport route under anaerobic conditions.

Modeling of electron transport pathways

Understanding the complex regulation of photosynthetic and connected respiratory electron transport components has serious limitations in intact photosynthetic systems. A powerful tool to circumvent this problem is provided by computer modeling of electron transport kinetics, which makes possible to follow any of the selected components. We have developed important modules of such a model and applied it support singlet-oxygen induced photodamage, as well as to interpret a novel phenomenon of oscillating changes in the yield of flash-induced variable Chl fluorescence. Currently we are working on modeling the whole network of the photosynthetic and respiratory electron transport.

Stress-induced defense and acclimation responses in cyanobacteria: We investigate the molecular background of various stress responses (high light, UV radiation, heavy metals, oxidative agents, oxygen availability etc.). Our recent interest includes the mechanism of heavy-metal- and 1O2-induced expression of Synechocystis 6803 genes.

Plant phenotyping

Understanding the acclimation of plants to adverse environmental stress factors requires the measurements of responses not only at the genomic, proteomic and metabolomic level, but also at the level of phenotypic changes. This approach is called plant phenotyping, which represents a rapidly growing field of plant sciences. We have developed a complex plant phenotyping platform, which allows medium-high throughput characterization of plant growth and physiological status. The platform is part of an EU-wide plant phenotyping infrastructure network (EPPN) and used to investigate the responses of various wheat and barley cultivars to stress induced by drought, nutrient limitation, salt, as well as to characterize the effect of plant growth enhancers to increase biomass of energy plants.

Selected publications

Vass, I. and Cser, K. (2009). Janus-faced charge recombinations in photosystem II photoinhibition. Trends Plant Sci. 14: 20-205.

I. Vass, Role of charge recombination processes in photodamage and photoprotection of the photosystem II complex, Physiologia Plantarum 142 (2011) 6-16.

P. Zhang, M. Eisenhut, A.-M. Brandt, D. Carmel, H. M. Silén, I. Vass, Y. Allahverdiyeva, T. A. Salminen, and E.-M. Aro, Operon flv4-flv2 provides cyanobacterial Photosystem II with flexibility of electron transfer, Plant Cell 24 (2012) 1952-1971.

Vass, I. Molecular mechanisms of photodamage in the Photosystem II complex, Biochim. Biophys. Acta (2012) 1817: 209-217.

A. U. Rehman, K. Cser, L. Sass, and I. Vass, Characterization of singlet oxygen production and its involvement in photodamage of Photosystem II in the cyanobacterium Synechocystis PCC 6803 by histidine-mediated chemical trapping, Biochim. Biophys. Acta 1827 (2013) 689-698.

Cseri, A. Sass, L. Törjék, O. Pauk, J. Vass, I., Dudits D. (2013) .Monitoring drought responses of barley genotypes with semi-robotic phenotyping platform and association analysis between recorded traits and allelic variants of some stress genes. Australian Journal of Crop Science7:1560-1570