|Jones, Tamara - UNIV OF ILLINOIS, URB|
Submitted to: Photosynthesis International Congress Symposium Proceedings and Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: June 28, 1995
Publication Date: N/A
Technical Abstract: In chilling-sensitive species such as tomato, low temperature stalls 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. 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 the 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. Our findings suggest that the "inappropriate" phosphorylation state caused by the low temperature-induced mistiming of the transcription of SPS-phosphatase underlies the chilling-sensitivity of photosynthesis in tomato.