About this project
The expression of the genes for the tetrameric Short-chain Alcohol Dehydrogenase-like proteins (SAD proteins) in plants, which were discovered by our research group about 15 years ago, increases dramatically by low intensity ultraviolet-B (UV-B) radiation (280–315 nm) and by a number of other abiotic stresses, both in leaf epidermal and mesophyll cells. UV-B treatment also leads to an increase in SAD protein content. The SADs belong to the short-chain dehydrogenase/reductase (SDR) superfamily of proteins, which is one of the largest known protein families and comprises thousands of members found in species ranging from bacteria to humans.
The physiological substrates of the SAD proteins have remained elusive but the SAD-C enzyme has been shown to reduce (non-physiological) one- or two-ring-membered quinones lacking long hydrophobic hydrocarbon tails. Immunohistochemical staining using a specific antiserum against the protein showed that high local concentrations of SAD are present in the protoderm of the seed cotyledonary axis in pea plants. Also, rows of cells in the ovary and the placental surface facing the ovule exhibited considerable SAD staining. Therefore, the different localization patterns of SAD, under normal conditions and under stress, suggest functions both in development and in responses to environmental stimuli.
At present, our efforts are concentrated to two biochemical issues of the SAD proteins:
- Determination of the three-dimensional structure of the SAD proteins by X-ray crystallography and NMR for later elucidation of the reaction mechanism of the chemical reaction that the SADs catalyze.
- Determination of the physiological substrate for SAD proteins in plants and their role in stress and development.
This project is also connected to the project: "Ultraviolet radiation as an environmental stimuli in biological systems: perception, signalling, molecular responses and morphogenesis".
Scherbak, N., Ala-Häiväla, A., Böwer, N., Strid, H., Grahn, E., Brosché, M., Eriksson, L.A., Gittins, J.R. & Strid, Å. (2011) The pea SAD short chain dehydrogenase/reductase: quinone reduction, tissue distribution, and heterologous expression. Plant Physiol. 155, 1839-1850.
Scherbak, N., Ala-Häivälä, A., Strid, H., Brosché, M., Öhrfelt, A., Nilsson, F. & Strid, Å. (2009) Expression of Pisum sativum SAD polypeptides in production hosts and in planta: tetrameric organization of the protein. Prot. Expr. Purif. 63, 18–25.
Gittins, J.R., Schuler, M.A. & Strid, Å. (2002) Identification of a novel nuclear factor-binding site in the Pisum sativum sad gene promoters. Biochim. Biophys. Acta 1574, 231-244.
Kalbin, G., Hidema, J., Brosché, M., Kumagai, T., Bornman, J.F. & Strid Å. (2001) UV-B-induced DNA damage and expression of defence genes under UV-B stress: tissue-specific molecular marker analysis in leaves. Plant Cell Environ. 24, 983-990.
Brosché, M. & Strid, Å. (1999) Cloning, expression and molecular characterisation of a stress-regulated cDNA encoding a short chain alcohol dehydrogenase. Plant Physiol. 121, 479-487.