Multiple regulation of Arabidopsis AtGST11 gene expression by four transcription factors under abiotic stresses.

The Arabidopsis thaliana glutathione S-transferase (GST; E.C. 2.5.1.18) gene, AtGST11, is regulated by a number of environmental stresses, including metal toxicities, oxidative stress and extremes of temperature. To clarify the mechanisms of this regulation, two transcription factors [(TFs), P1-1 and P1-3] were isolated by yeast one-hybrid (Y1H) analysis and characterized. These TFs encoded a putative bZIP TF (AtbZIP30) and ethylene-response element-binding factor 2 (AtERF2), respectively. Y1H and electrophoresis mobility shift assay (EMSA) showed that both proteins bound to the 5'-upstream region of the AtGST11 gene. Promoter activity assays indicated that both TFs upregulate AtGST11. In addition, another two previously isolated TFs (#13 and #43), encoding C3 HC4 -type RING finger (DAL1) and Homeobox protein 6 (AtHB6), respectively, were found to downregulate. Expression of the AtGST11 gene in a wild-type line (Col-0) was increased by Cd, Cu and Al, but decreased by cold, heat and diamide treatment. To determine how each TF relates to the environmental regulation of the AtGST11 gene, quantitative real-time polymerase chain reaction was performed using RNA samples derived from two disrupted mutant lines (ΔDAL1 and ΔAtHB6) or an over-expression line (oxAtERF2) under various stresses. The results indicated that DAL1 and AtHB6 downregulated the expression of AtGST11 under, most of the stresses tested as, repressors and AtERF2 upregulated the expression under heat stress as inducer.

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