Functional characterization of an abiotic stress-inducible transcription factor AtERF53 in Arabidopsis thaliana
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AP2/ERF proteins play crucial roles in plant growth and development and in responses to biotic and abiotic stresses. ETHYLENE RESPONSE FACTOR 53 (AtERF53) belongs to group 1 in the ERF family and is induced in the early hours of dehydration and salt treatment. The functional study of AtERF53 is hampered because its protein expression in Arabidopsis is vulnerable to degradation in overexpressed transgenic lines. Taking advantage of the RING domain ligase1/RING domain ligase2 (rglg1rglg2) double mutant in which the AtERF53 can express stably, we investigate the physiological function of AtERF53. In this study, we demonstrate that expression of AtERF53 in wild-type Arabidopsis was responsive to heat and abscisic acid (ABA) treatment. From results of the cotransfection experiment, we concluded that AtERF53 has positive transactivation activity. Overexpression of AtERF53 in the rglg1rglg2 double mutant conferred better heat-stress tolerance and had resulted in higher endogenous ABA and proline levels compared to rglg1rglg2 double mutants. AtERF53 also has a function to regulate guard-cell movement because the stomatal aperture of AtERF53 overexpressed in rglg1rglg2 double mutant was smaller than that in the rglg1rglg2 double mutant under ABA treatment. In a global gene expression study, we found higher expressions of many stress-related genes, such as DREB1A, COR15A, COR15B, PLC, P5CS1, cpHSC70 s and proline and ABA metabolic-related genes. Furthermore, we identified several downstream target genes of AtERF53 by chromatin immunoprecipitation assay. In conclusion, the genetic, molecular and biochemical result might explain how AtERF53 serving as a transcription factor contributes to abiotic stress tolerance in Arabidopsis.
KeywordsAP2/ERF transcription factor AtERF53 Abiotic stress Chromatin immunoprecipitation assay
This work was supported by the National Science Council, Taiwan (grant no. NSC98-2311-B-002-012-MY3), and National Taiwan University (grant no. 98R0066-35). We thank Prof. Andreas Bachmair for providing the rglg1rglg2 double mutant and Prof. Ohme-Takagi for the GAL4-LUC reporter. Thanks also go to Dr. W.-H. Cheng of Academia Sinica for the technique of ABA quantification, and Dr. Keqiang Wu of National Taiwan University of ChIP assay.
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