Responsiveness and Adaptation to Salt Stress of the REDOX-RESPONSIVE TRANSCRIPTION FACTOR 1 (RRTF1) Gene are Controlled by its Promoter

The REDOX-RESPONSIVE TRANSCRIPTION FACTOR 1 (RRTF1) gene encodes a member of the ERF/AP2 transcription factor family involved in redox homeostasis. The RRTF1 gene shows tissue-specific responsiveness to various abiotic stress treatments including a response to salt stress in roots. An interesting feature of this response is an adaptation phase that follows its activation, when promoter levels revert to a base line level, even if salt stress is maintained. It is unclear if adaption is controlled by a switch in promoter activity or by changes in transcript levels. Here we show that the RRTF1 promoter is sufficient for the control of both activation and adaptation to salt stress. As constitutive expression of RRTF1 turned out to be detrimental to the plant, we propose that promoter-regulated adaptation evolved as a protection mechanism to balance the beneficial effects of short-term gene activation and the detrimental effects of long-term gene expression.