|Jones, Tamara - U OF ILLINOIS, URBANA|
Submitted to: Plant Physiology Supplement
Publication Type: Proceedings
Publication Acceptance Date: June 15, 1995
Publication Date: N/A
Technical Abstract: Overnight low-temperature treatment reduces photosynthesis in chilling-sensitive species, such as tomato and cucumber, by as much as 60%. One effect of this treatment is to stall the endogenous rhythm controlling transcription of certain nuclear encoded genes causing the synthesis of the corresponding transcripts and proteins to be temporally mistimed when the plant is rewarmed. It is likely that mistiming the synthesis of proteins involved in the regulation of photosynthesis underlies the chilling sensitivity of photosynthesis in these plant species. We have shown that the activity of sucrose phosphate synthase (SPS), a key enzyme controlling the sucrose biosynthetic pathway, has both a diurnal and circadian rhythm in tomato, and that these rhythms are delayed by chilling treatments. We have further demonstrated that the SPS protein level does not vary and is unaffected by short term low temperature episodes that cause shifts in pattern of SPS activity. Using specific kinase and phosphatase inhibitors we have shown that the daily pattern of SPS activity is the result of phosphorylation and dephosphorylation of the protein. The sensitivity of the pattern in SPS activity to specific inhibitors of transcription and translation revealed expression of the gene coding for SPS phosphatase is responsible for the diurnal and circadian rhythm in SPS activity.