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Title: PROTEIN PHOSPHORYLATION MEDIATES A KEY STEP IN SUCROSE-REGULATION OF A PROTON-SUCROSE SYMPORTER

Author
item RANSOM-HODGKINS, WENDY - PLANTBIO UI URBANA
item VAUGHN, MATTHEW - PLANTBIO UI URBANA
item BUSH, DANIEL

Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 8/8/2002
Publication Date: 12/20/2003
Citation: RANSOM-HODGKINS, W., VAUGHN, M., BUSH, D.R. PROTEIN PHOSPHORYLATION MEDIATES A KEY STEP IN SUCROSE-REGULATION OF A PROTON-SUCROSE SYMPORTER. PLANT PHYSIOLOGY SUPPLEMENT. 2003. v. 218. p. 121-130.

Interpretive Summary:

Technical Abstract: Assimilate partitioning is the term used to describe the process of distributing organic nutrients from source to sink tissues. Recent research in this field has strived to identify key steps in this process that regulate the balance between source production and sink demand of photo assimilates. An important advance in this area was the recent discovery that proton-sucrose transport activity in sugar beet leaf tissue is modulated by dynamic changes in sucrose concentration in the phloem. Sucrose transport activity measured in plasma membrane vesicles isolated from leaves fed with sucrose decrease in activity compared to water fed controls. There is a parallel drop in symporter message abundance and recent results showed that this decrease is the result of diminished rates of symporter transcription. Here we show that protein phosphates inhibitors decrease transport activity and the transcription rate of the symporter. In contrast, protein kinase inhibitors had no effect or increased both transcription and transport activity. Furthermore, pre-feeding leaves with kinase inhibitors before feeding with sucrose blocked the sucrose-dependent decrease in symporter activity and expression. To investigate transcriptional regulation in more detail, we have cloned 1.2 kb of the promoter region of the sugar beet proton/sucrose symporter to identify regulatory elements associated with sucrose regulation. These data provide a basis for a model where phosphorylation/dephosphorylation of components of a sucrose-signaling pathway regulate the capacity for sucrose transport between source and sink tissues in the plant.