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United States Department of Agriculture

Agricultural Research Service

Title: Clocks That don't Work in the Cold, Chilling Delays Cricadian Pattern of Sucrose Pattern of Sucrose Phosphate Synthase and Nitrate Reductase Activity in Tomato

item Ort, Donald

Submitted to: Workshop on Crop Development for Cool and Wet Climate of Europe
Publication Type: Abstract Only
Publication Acceptance Date: October 21, 1998
Publication Date: N/A

Technical Abstract: Overnight low-temperature exposure reduces photosynthesis in chilling-sensitive species, such as tomato and cucumber, by as much as 60 percent. We have shown that one intriguing effect of low temperature on chilling sensitive plants is to stall the endogenous rhythm controlling transcription of certain nuclear-encoded genes causing the synthesis of the corresponding transcripts and proteins to be mistimed when the plant is rewarmed. In addition, we found that the circadian rhythm controlling the activity of sucrose phosphate synthase (SPS) and nitrate reductase (NR), key control points of carbon and nitrogen metabolism in plant cells, is delayed in tomato by chilling treatments. Using specific protein kinase and phosphatase inhibitors, we further demonstrate that the chilling-induced delay in SPS and NR activity is the result of corresponding delays in the pattern of the phosphorylation status of the proteins. The sensitivity of the pattern in SPS activity to specific inhibitors of transcription and translation indicate that the chilling-induced delay in SPS phosphorylation status is caused by an effect on expression of the gene coding for SPS phosphatase. In contrast, the chilling-induced delay in NR activity does not appear to arise from effects at the level of gene transcription. It is likely that the mistiming in the regulation of SPS and NR, and perhaps other key metabolic enzymes, underlies the chilling sensitivity of photosynthesis in these plant species.

Last Modified: 4/22/2015
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