|Tucker, Dawn - LIFE SCIENCES UOFI URBANA|
Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 15, 2000
Publication Date: N/A
Technical Abstract: Exposures to overnight chilling episodes in chilling sensitive species such as Lycopersicon esculentum cause declines in following day photosynthetic efficiency. Previous research in our lab indicates that dark chilling in such species may, in fact, stall the endogenous rhythms that coordinate multiple important enzyme activities. Nitrate Reductase catalyzes the first and rate limiting step of nitrate assimilation and is one of the enzymes exhibiting this low temperature effect. Early observations suggest that NR activity as well as NR protein and message levels all display a robust rhythmic pattern following a roughly 24hr oscillation with minimums occurring during subjective night periods. Rhythms in both activity and enzyme level show distinctive cold-induced displacement during the following day. Northern blots indicate that a similar effect also occurs at the message level. The disturbance in transcript accumulation, however, is brief and independent of the time of day that the chill is applied, suggesting a general reaction of NR gene expression to cool temperatures rather than a specific shift in NR rhythmic behavior. Western blots have directly confirmed the existence of an endogenous rhythm at the NR protein level and synchronous sampling of protein and RNA extracts promise to more clearly define the complex relationship between dark chilling effects on NR message and subsequent protein and activity rhythms.