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Updated: Sep 30, 2026

An Induction System for Clustered Stomata by Sugar Solution Immersion Treatment in Arabidopsis thaliana Seedlings
Published on: February 15, 2019
Sucrose-mediated transcriptional regulation of sucrose symporter activity in the phloem
Matthew W Vaughn1, Gregory N Harrington, Daniel R Bush
1Program in Physiological and Molecular Plant Biology, University of Illinois at Urbana-Champaign, Urbana IL, 61801, USA.
Abstract:
A proton-sucrose symporter mediates the key step in carbon export from leaves of most plants. Sucrose transport activity and steady-state mRNA levels of BvSUT1, a sugar beet leaf sucrose symporter, are negatively regulated specifically by sucrose. Results reported here show that BvSUT1 mRNA was localized to companion cells of the leaf's vascular system, which supports its role in the systemic distribution of photoassimilate. Immunoblot analysis showed that decreased transport activity was caused by a reduction in the abundance of symporter protein. RNA gel blot analysis of the leaf symporter revealed that message levels also declined, and nuclear run-on experiments demonstrated that this was the result of decreased transcription. Further analysis showed that symporter protein and message are both degraded rapidly. Taken together, these data show that phloem loading is regulated by means of sucrose-mediated changes in transcription of a phloem-specific sucrose symporter gene in a regulatory system that may play a pivotal role in balancing photosynthetic activity with resource utilization.
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