Project Details


Sulfate assimilation is the pathway by which inorganic sulfate (SO42-) is reduced for cysteine synthesis. Cysteine is an important amino acid with many different functions. This proposal focuses on its role as the precursor of glutathione an important antioxidant in plants.

The enzyme APS reductase, which produces sulfite (SO32-) from 5-adenylylsulfate (APS), catalyzes an essential step in sulfate assimilation. Experimental evidence has been obtained that APS reductase is activated by oxidation. The proposal hypothesis is that APS reductase plays a key role in regulation of glutathione synthesis under conditions of oxidative stress. Therefore, it may be an important component in the plant response to oxidative stress.

In the work proposed the project hypothesis will be tested by exploring the mechanism and physiological effect of APS reductase regulation. APS reductase genes have been cloned from several different plant species. Each will be studied for the ability to be regulated by oxidative conditions. It is believed that the mechanism of APS reductase regulation relies on two cysteine residues in the protein that can form a disulfide bond. The state of the cysteine residues of the enzyme will be analyzed. Finally, the physiological effect of bypassing the APS reductase step by expressing bacterial homologs in transgenic plants will also be studied.

This work will provide new insight into an important facet of plant response to oxidative stress, the mechanism for regulation of glutathione synthesis. APS reductase is one of a small group of enzymes that are activated by oxidative stress conditions. The novelty of this system and the connection with oxidative stress are compelling reasons for further study of APS reductase.

Effective start/end date9/1/998/31/03


  • National Science Foundation: $310,000.00


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