High REDOX RESPONSIVE TRANSCRIPTION FACTOR1 Levels Result in Accumulation of Reactive Oxygen Species in Arabidopsis thaliana Shoots and Roots.

Redox Responsive (RRTF1) in Arabidopsis is rapidly and transiently upregulated by H2O2, as well as biotic- and abiotic-induced redox signals. RRTF1 is highly conserved in angiosperms, but its physiological role remains elusive. Here we show that inactivation of RRTF1 restricts and overexpression promotes reactive oxygen species accumulation in response to stress. Transgenic lines overexpressing RRTF1 are impaired in root and shoot development, light sensitive, and susceptible to Alternaria brassicae infection. These symptoms are diminished by the beneficial root endophyte Piriformospora indica, which reduces accumulation locally in roots and systemically in shoots, and by antioxidants and duanyu1670 inhibitors that scavenge More than 800 genes were detected in mature leaves and seedlings of transgenic lines overexpressing RRTF1; ∼ 40% of them have stress-, redox-, defense-, cell death- and senescence-related functions. Bioinformatic analyses and in vitro DNA binding assays demonstrate that RRTF1 binds to GCC-box-like sequences in the promoter of RRTF1-responsive genes. Upregulation of RRTF1 by stress stimuli and H2O2 requires WRKY18/40/60. RRTF1 is co-regulated with the phylogenetically related RAP2.6, which contains a GCC-box-like sequence in its promoter, but transgenic lines overexpressing RAP2.6 do not accumulate higher duanyu1670 levels. RRTF1 also stimulates systemic duanyu1670 accumulation in distal non-stressed leaves. We conclude that the elevated levels of the highly conserved RRTF1 induce duanyu1670 accumulation in response to duanyu1670 and abiotic and biotic stress signals.

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