Epsilon Archive for Student Projects

Abstract

Barley is one of the most important cereals cultivated in the Nordic countries. Climate change brings warmer and moisture climate which favors fungal diseases. In the cropland barley can be seriously infested with hard fungus attack. Since it is important that the yield bears a high quality it is of great importance to find varieties more resistant to attacks.
Pathogenesis-related (PR) proteins are stress proteins induced in the plant in response to infection and abiotic stress (van Loon, 1997). PRs are shown to have antimicrobial activity differing between bacteria, fungi and oomycetes (Tandrup Poulsen, 2001). Among the 17 PR-families (van Loon et al., 1994, 2006) PR-5 is one of the most abundant ones in barley (Tandrup Poulsen, 2001, van Loon et al., 2006).
Studies have shown that PR-5 exists naturally in the ground tissue of leaves, but not in the epidermis (Gregersen et al., 1997). In the epidermal cell walls an epidermis-specific promoter for PR-5 has been placed in front of the gene encoding PR-5, this to achieve a more resistant cultivar of barley. Enhanced resistance has been demonstrated, but it is not confirmed that this resistance is due to expression of PR-5 in epidermis (Santén et al., unpublished, Tandrup Poulsen, 2001). In the modified lines, preliminary studies have shown irregular structure of epidermis (Santén et al., unpublished).
The aim of the study was to establish whether there were structural differences between regular and modified barley, and to localize PR-5 in epidermis. Counterstaining was used to be able to study the leaf structure in microscope, and immunocytochemistry was used to localize PR-5.
Results showed irregular cell structure in epidermis, and in a few cases even in the ground tissue, of modified barley. Due to failure in method, unspecific binding of the antibody visualizer occurred and no confident result could be established regarding the localization of PR-5. Nothing indicates an existence of PR-5 in epidermal cell walls of modified barley. This could be a result of a non-working method, undetectable levels of PR-5 or that the gene encoding PR-5 is expressed as mRNA but not translated to protein.
Occurrence of PR-5 has been demonstrated in epidermal cells of infected material. This detection could be due to the fact that the gene needs an infection to be
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expressed as the protein. More studies are necessary to establish whether the showed enhanced resistance is due to expression of PR-5 in epidermis.