Group leader: Dr. Horváth Ferenc

I. The role of nitric oxide in membrane transport and photosynthesis

Nitric oxide (NO), gaseous free radical, is a recently identified component of the response to abiotic stress in plans. Its signalization pathway and mechanism is only partly elucidated. NO has been shown to be involved in regulation of cell division and cell death as well as response to pathogens and drought stress. The research group focuses on investigating the role of NO in photosynthesis and membrane transport processes with a special emphasis on guard cells.

We measured QA- reoxidation kinetics of intact leaves treated with NO donors and revealed that NO slows down primary charge separation in PSII in vivo through binding to the QAFe2+QB complex. Experiments carried out in the presence of DCMU show that NO inhibits charge separation between QA- and the S2 state of the water-oxidizing complex and also interacts with the YD˙ tyrosine residue of PSII. Out aim is to investigate the role of NO in guard cell photosynthesis which differs from mesophyll cell photosynthesis.

The signaling role NO during stomatal closure – experiments with Shaker-channels in heterologous expression system.

Guard cells are specialized plant cells which influence the rate of water and gas exhange by changing their turgor. The rapid opening and closure of stomata is mediated by ion channels which allow the passage of potassium across the plasma membrane. The mechanisms regulating the gating of ion channels are complex, depending on environmental factors as well as the physiological status of the plant. Drought stress leads to elevated levels of abscisic acid, which in turn induce stomatal closure via three signal transduction pathways. NO is involved in the Ca-dependent pathway: it increases the level of intracellular CS thus inactivates the Ca-dependent, inward rectifying potassium current.

NO has been shown to directly regulate Shaker-channels in animal systems through S-nitrosylation of the cystein residue of the channel protein. Our goal is to examine the effects of a potential nitrosylation of homo- and heterotetramer Shaker-channels in a HEK293 heterologous expression system.

II. THE ROLE OF STOMATAL REGULATION IN THE PLANT IMMUNE RESPONSE

OTKA Project (2010-2014)

Elements of the signal transduction pathway leading to stomatal closure are of special importance, gaining as much interest in plant science as the role of abiotic factors. The aim of the present study is to explore how microbe-associated molecular patterns (MAMPs) and endogenous elicitors (DAMPs) cause stomatal closure and thus takes part in basal resistance (BR); and how guard cell (GC) photosynthesis and membrane transport contribute to this signalling pathway.

Based on our previous results we suspect that the MAMP and DAMP chemicals to be tested in this study inhibit linear photosynthetic electron transport via inducing nitric oxide synthesis. Certain virulence factors are capable of reopening the stomata and thus facilitate the penetration of pathogens, therefore interaction between the BR and the specific resistance signalling pathways of GCs will also be investigated. Reactive oxygen species of the signalling pathway are identified by using fluorescent sensors in the GCs of receptor- and signalling-mutants of Arabidopsis with confocal laser scanning microscopy. Photosynthetic activity of single GCs are measured with a microscopy-pulse-amplitude modulation chlorophyll fluorometer (Microscopy-PAM). Membrane transport of GC protoplasts are patch clamped in the conventional whole-cell mode.

Group members

Dr. Horváth Ferenc PhD
Dr. Wodala Barnabás PhD
Ördög Attila, PhD student
Gábor Fábián, MSc student

Conference abstracts

F Horváth, A Ördög, T Rózsavölgyi, B Wodala. Nitric oxide modulates guard cell photosynthesis. (2010) 3rd Plant NO Club International Meeting July 15-16 2010, Olomouc, Czech Republic, Abstract L8 p. 17. ISBN 978-80-903545-0-0 (invited speaker)

A Ördög, T Rózsavölgyi, B Wodala, Zs Deak, I Tari, F Horváth. Effect of chitosan on guard cell photosynthesis. (2010) XVII Congress of the Federation of European Societies of Plant Biology (FESPB) 4-9 July 2010, Valencia, Spain, Book of Abstracts P17-024 p. 186. (poster)

Relevant publications

Wodala B, Ordog A, Horvath F. The cost and risk of using sodium nitroprusside as a NO donor in chlorophyll fluorescence experiments. (2010) Journal of Plant Physiology, 167(13): 1109-1111. IF 2.437

Wodala, B., Deák, Zs., Vass, I., Erdei, L., Altorjay, I., Horváth, F. In vivo target sites of NO in photosynthetic electron transport as studied by chlorophyll fluorescence in pea leaves (2008) Plant Physiology, 146 (4):1920-1927. IF 6.11

A Ördög, B Wodala, F Horváth Investigating the role of potassium channel KAT1 in NO mediated stomatal closure.  Acta Biol Szeged 2008, 52(1):163-165

T Rózsavölgyi, F Horváth Effect of pyrethroid insecticides on the photosynthetic activity of pea mesophyll protoplasts. Acta Biol Szeged 2008, 52(1):233-235.

B Wodala, F Horváth The effect of exogenous NO on PSI photochemistry in intact pea leaves. Acta Biol Szeged 2008, 52(1):243-245

Hertel, B., Horváth, F., Wodala, B., Hurst, A., Moroni, A., Thiel, G. KAT1 inactivates at sub-millimolar concentrations of external potassium (2005) Journal of Experimental Botany, 56 (422), Pages 3103-3110. Cited 5 times. IF: 3.336.

Horváth, F., Erdei, L., Wodala, B., Homann, U., Thiel, G. K+ outward rectifying channels as targets of phosphatase inhibitor deltamethrin in Vicia faba guard cells (2002) Journal of Plant Physiology, 159 (10), Pages 1097-1103. Cited 1 time. IF 0.941

Moroni, A., Viscomi, C., Sangiorgio, V., Pagliuca, C., Meckel, T., Horvath, F., Gazzarrini, S., (...), Thiel, G. The short N-terminus is required for functional expression of the virus-encoded miniature K+ channel Kcv (2002) FEBS Letters, 530 (1-3), Pages 65-69. Cited 17 times. IF 3.912

Scientific partners

Biological Research Center, Institute of Plant Biology, Molecular Stress- and Photobiology Group (Dr. Éva Hideg and Dr. Imre Vass) Szeged, Hungary

Darmstadt University of Technology, Institute of Botany, Membrane Biophysics (Prof. Gerhard Thiel) Darmstadt, Germany