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ARS Home » Research » Publications at this Location » Publication #115600
Title: REGULATION OF GENE EXPRESSION: SUCROSE REGULATION OF A PROTRON-SUCROSE SYMPORTER

Author
item VAUGHN, MATTHEW - PLANT BIOLOGY UOFI URBANA
item RANSOM-HODGKINS, WNEDY - PLANT BIOLOGY UOFI URBANA
item BUSH, DANIEL

Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/19/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: A proton-sucrose symporter mediates the key transport step in plants that utilize apoplastic phloem loading. We have described a previously unknown pathway in which sucrose acts as a signaling molecule in a pathway that appears to regulate the activity of the sucrose symporter in sugar beet. Kinetic analysis of sucrose uptake suggested that this regulation in activity was caused by changes in the abundance of symporter protein. Recent Western analysis of symporter abundance supports that conclusion. RNA gel blot analysis of the leaf symporter showed that symporter message decreased. Nuclear run-off experiments showed that this was the result of decreased transcriptional activity. Reduced sink strength is predicted to cause repression of symporter activity, accumulation of photoassimilate in source tissues and, ultimately, reduced photosynthetic activity. In beets where sink demand was decreased by chilling, source leaf sucrose concentrations increased and sucrose uptake declined by an average of 20 percent. Taken together, these results support our working hypothesis that this response pathway regulates assimilate partitioning and photosynthetic activity by modulating phloem loading in response to changing levels of "sink demand."