Plants, lacking a circulatory system, have developed a defense against pathogen attack based on the ability of each cell to recognize invaders. Once this initial recognition occurs, the plant has many responses to the pathogen, including local programmed cell death, removing the pathogen’s nutrient source, and increased transcription of genes coding for phytoalexins (antimicrobial molecules). The plant also increases production of reactive oxygen species, one of which is hydrogen peroxide. Hydrogen peroxide plays a varied role in plant defense, including strengthening of the cell wall around the infected area, assisting with local programmed cell death by attacking the thiol groups of proteins, and playing a poorly understood role in prompting transcription of defense genes in surrounding cells. Normally, catalase, an enzyme, would remove hydrogen peroxide before it could affect the cell. Our lab’s hypothesis is that catalase modulates plant defense response.
In order to test this hypothesis, we are trying to find a catalase clone from bean (Phaseolus vulgaris) plants, our model system. We have isolated four putative catalase clones from a lambda Zap II cDNA library, all of which have been restriction mapped, and two of which have been partially sequenced. We are working on sense/anti-sense determination for these two. One of these two has a strong potential to be a catalase gene in bean. The partial sequence came back with several catalase homologous matches from a search of a national database of 400,000 sequences.
Kari Christensen, ’99 Brush Prairie, WA
Jason Downing, ’99 Bellevue, NE
Majors: Biochemistry and Molecular Biology, Biology
Sponsor: Craig Tepper