Overall objective: To understand and distinguish the roles of mesophyll, bundle sheath and stomata guard cells in a holistic approach to plant defence and acclimatory responses.
Group focus: We would like to characterize excess light induced systemic acquired acclimation (SAA) versus pathogen induced systemic acquired resistance (SAR). We are testing pathogen related mutants (lsd1, eds1, pad4, cpr1, 5, 6, ein2 and sid2 and others) in acclimatory responses to high and excess light. Similarly, we are analysing photooxidative stress tolerant and sensitive mutants (cao, gpx7, rax1-2, cry1, npl1, pot1, pot2, pot3 cry1), in response to pathogen infection. We are using a combination of genetic, molecular, biochemical and biophysical approaches to understand how these proteins perform their respective roles in plant defence and acclimatory mechanisms, and discover which cellular processes they alter.
Research projects, which are undertaken, will have an impact on knowledge concerning plants' disease rezistance and acclimatory mechanisms to harsh environmental conditions (e.g. photooxidative stress caused by low temperature and high light). This knowledge is necessarily for development of novel methods for improvement of abiotic and biotic stress tolerance in plants without compromising growth and development. Successful strategies for the improvement of broad spectrum of stress tolerance in plants will enable swedish seed companies, plant breeding companies, plant improvement institutions and horticultural institutes. Such successful strategies will also lead to more-environment friendly agriculture and enhanced plant health and therefore to potentially enhanced nutritional value of importance for consumer. The research projects in the group are supported by Swedish and EU Foundations.
Figure 1. Systemic transmission of excess light signals in bundle sheath cells.
A: Systemic induction of APX1 expression in both root and shoot after illumination of a part of the rosette (white ellipse) with µE. APX1 expression was visualized by a transgenic promoter-luciferase fusion. False colours give relative luminescence units. SAA = systemic acquired acclimation (Karpinski et al., ) is associated with changes in plasmamembrane hyperpolaryzation, photo- and non-photochemical quenching, and levels of ethylene H2O2, and ABA. B: Visualization of systemic APX2induction specifically in the vascular tissue of a mature leaf after 30 min illumination with excess light. C: Staining of H2O2 in the bundle sheath cells of the vascular tissue with H2DCF-DA (yielding green fluorescence after reaction with H2O2) in a mature leaf after pathogen infection. Similar, but slightly weaker signals were observed in both local and systemic leaves after treatment with excess light. Note the overlapping patterns of H2O2 accumulation and APX2 expression. D: Hyperpolarization of the membrane potential of bundle sheath cells during 800 ms pulses of excess light ( µE). Orange arrows indicate start, black arrows indicate stop of light pulses.
Slesak, I., Karpinska, B., Surówka, E., Miszalski, Z. and Karpinski, S. () Redox changes in the chloroplast and hydrogen peroxide are essential for regulation of C3-CAM transition and photooxidative stress responses in the facultative CAM plant Mesembryanthemum crystallinum L. Plant Cell Phys. 6: in press.
Karpinski, S., Gabrys, H., Karpinska, B. and Mullineaux, P. () Light perception in plant disease defence mechanisms. Curr. Op. Plant Biol. 6: in press.
Fryer, M.J., Ball, L., Oxborough, K., Karpinski, S., Mullineaux, P.M. and Baker, N.R. . Control of Ascorbate peroxidase 2 expression by hydrogen peroxide and leaf water status during excess light stress reveals a functional organisation of Arabidopsis leaves. Plant J. 33: 691-705.
Mullineaux, P. and Karpinski, S. () Signal transduction in response to excess light: getting out of the chloroplast. Cur. Op. Plant Biol. 5: 43-48.
Mullineaux, P., Ball, L., Escobar, C., Karpinska, B., Creissen, G. and Karpinski, S. () Are diverse signalling pathways integrated in the regulation of Arabidopsis antioxidant defence gene expression in response to excess excitation energy? Phil. Trans. R. Soc. Lond. 355: .
Karpinska, B. Wingsle, G. and Karpinski, S. () Antagonistic effects of hydrogen peroxide and glutathione on acclimation to excess excitation energy in Arabidopsis. IUBMB Life 50: 21-26.
Karpinski, S., Reynolds, H., Karpinska, B., Creissen, G., Wingsle, G. and Mullineaux, P. () Systemic signalling and acclimation in response to excess excitation energy in Arabidopsis. Science 284: 654-657.
Mullineaux, P.M., Karpinski, S., Jimenéz, A., Cleary, S.P., Robinson, C. and Creissen, G. () Identification of cDNAs encoding plastid-targeted glutathione peroxidase. Plant J. 13: 375-379.
Karpinski, S., Escobar, C., Karpinska, B., Creissen, G. and Mullineaux, P. () Photosynthetic electron transport regulates the expression of cytosolic ascorbate peroxidase genes in Arabidopsis during excess light stress. Plant Cell 9: 627-640.
