Dr. Becker's laboratory is interested in the regulation of nuclear genes encoding enzymes that are involved in the process of photorespiration and localized in leaf peroxisomes. The expression of these genes is organ specific, developmentally regulated, and strongly modulated by light, as studied in emerging cucumber seedlings. He has recently isolated cDNA and genomic clones for two photorespiratory enzymes, hydroxypyruvate reductase (HPR) and serine:glyoxylate aminotransferase (SGAT), and have sequenced an HPR clone containing the entire coding region plus 2.2kb of 5' flanking sequence. Here, he proposes to confirm (by nuclear run-on studies) the transcriptional regulation suggested by prior mRNA assays and transcript analyses. He then intends to use the isolated clones to assay for cis acting regulatory elements (be deletion analysis in transgenic tobacco), trans acting factors (by gel shift and foot printing assays), and possible changes in chromatin structure accompanying both developmental and light regulation. %%% The process of photorespiration is linked to but independent of photosynthesis. The function of photorespiration for the plant is to return to the Calvin cycle three out of every four carbon atoms diverted from it by the oxygenase activity of the carbon dioxide fixing enzyme of the photosynthetic cycle. This is of major metabolic importance to the plant. The regulation of the enzymes of that pathway are the topic of the current study.
