What Stimulates GST Levels in Plants?

Transcriptional Regulation

• Regulation of gene expression is complex and can take place at multiple levels. As with other genes, expression of GSTs is regulated by transcription factors: proteins that act like switches to turn expression of a given gene on or off. As noted in a 2002 review in the journal Genome Biology, it's currently believed that regulation of GST expression takes place primarily at the level of transcription, although many of the pathways involved are still poorly understood and remain a subject of current research.

Differentiation

• Different tissues in plants show different patterns of GST expression and thus different levels of these proteins. According to the 2002 review in Genome Biology, pollen in one inbred maize line was been found to contain only one kind of GST protein, while some other parts of the plant contained multiple kinds. Scientists have found it possible, however, to override these differences by treating the plants with chemicals like herbicide safeners.

Treatment

• Herbicide safeners are chemicals that help protect a non-target species like a crop plant from the deleterious effects of a herbicide. Safeners work by promoting production of enzymes, like certain GSTs, that detoxify herbicides and other chemicals that threaten the plant's survival. Exposure to herbicides can also increase levels of GSTs in many cases, although this effect may be due to the injury caused the plant rather than any specific action of the herbicide itself.

Other Factors

• Levels of several GSTs rise sharply during cell division and following exposure to certain plant hormones like auxins and cytokinins. Infection with plant pathogens also tends to increase GST levels, as does osmotic stress -- a condition where increasing soil salt content makes it more difficult for the plant to take up water. In some instances, these stresses can actually cause plant cells to produce a different variant of a given GST through a process called alternate splicing.