Author
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CHIOU, TZYY-JEN - PLANT BIOLOGY UOFI URBANA |
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BUSH, DANIEL |
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Submitted to: Plant Physiology Supplement
Publication Type: Abstract Only Publication Acceptance Date: 8/6/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Chlorsulfuron is a commonly used herbicide whose primary target is acetolactate synthase (ALS), a key enzyme that catalyzes the first step in branched chain amino acid biosynthesis. In addition to the obvious consequences such inhibition will have on protein biosynthesis, several papers have reported that an early effect of chlorsulfuron is sucrose accumulation in the treated leaves, thus implicating a direct impact on phloem loading. Because of our laboratory's general interest in assimilate partitioning, we investigated the impact of chlorsulfuron on the activity and/or regulation of the proton-sucrose symporter. Detached leaves of sugar beet were treated with chlorsulfuron and transport activity was subsequently measured in vivo with leaf discs or in vitro using purified plasma membrane vesicles. Sucrose transport activity was unaltered in both assays after 24 hr treatments with 0.1 to 0.5 mM chlorsulfuron. Soluble sugar content and vanadate-sensitive ATPase were also unaffected. Nevertheless, necrotic symptoms were observed in the major and miner veins, and petioles 6 days after treatment. These results suggest chlorsulfuron does not alter the activity, expression, or regulation of the sucrose symporter. In addition, the absence of sugar accumulation in these experiments suggests sugar accumulation is not directly linked to plant mortality. |
