Stimulus-reversible Co-repression in Regulation of a Plant bZIP Factor

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Biotic and industrial activities result in the environmental accumulation of organic toxins. Cellular protection against such "xenobiotic stress" agents is afforded by increasing the rate of transcription of nuclear detoxification genes, through changes in the activity of basic/leucine-zipper (bZIP) transcription factors. Key structural and regulatory features of xenobiotic-responsive bZIP factors of animals and yeast have been elucidated. By comparison, less is known about their functional counterparts in plants. The long-term goal of this research is to understand how transcription involving a tobacco bZIP factor termed TGA1a is regulated by cellular and stress cues. Recently it has been shown that xenobiotic stress induced by 2,4-dichlorophenoxyacetic acid can stimulate DNA-binding and trans-activation functions of TGA1a. A nuclear TGA1a-binding protein termed p120, with properties of a co-repressor, is strongly implicated in stress-responsive regulation of these transcription activities. The PI's laboratory will investigate the mode of action of the p120 co-repressor, through in vivo functional studies with its cloned gene. TGA1a and its cognate as-1-type cis-elements have been implicated in the regulation of a number of plant detoxification and host-defense genes. Thus, elucidating the molecular basis of this transcriptional response pathway is important for advancing basic knowledge of cellular detoxification processes, and for developing effective genetic strategies to manipulate natural protective genes of plants. Because xenobiotic toxins accumulate in crop plants and retain significant latent activity, research aimed at understanding plant transcriptional control of detoxification pathways may have important implications for human health.