The SLIM1 transcription factor is required for arsenic resistance in Arabidopsis thaliana

Abstract

The transcriptional regulators of arsenic-induced gene expression remain largely unknown. Sulfur assimilation is tightly linked with arsenic detoxification. Here, we report that mutant alleles in the SLIM1 transcription factor are substantially more sensitive to arsenic than cadmium. Arsenic treatment caused high levels of oxidative stress in the slim1 mutants, and slim1 alleles were impaired in both thiol accumulation and sulfate accumulation. We further found enhanced arsenic accumulation in roots of slim1 mutants. Transcriptome analyses indicate an important role for SLIM1 in arsenic-induced tolerance mechanisms. The present study identifies the SLIM1 transcription factor as an essential component in arsenic tolerance and arsenic-induced gene expression. Our results suggest that the severe arsenic sensitivity of the slim1 mutants is caused by altered redox status.

Keywords: Arabidopsis thaliana; arsenic; sulfur limitation; transcription factor.

Figure 1.. Root growth inhibition of slim1 mutants grown on cadmium or arsenic-containing media.

The slim1–1 and slim1–2 mutant alleles were compared to wild-type controls (WT) grown on control minimal media and media containing 30 μM Cd or 10 μM As(III) for 7 days (A - D). Root growth was quantified using ImageJ (one-way ANOVA, Tukey HSD).

Figure 2.. slim1 mutants accumulate arsenic in roots and have high antioxidant activity when exposed to arsenic.

slim1 mutants grown on arsenic-containing media accumulate arsenic in the shoots when grown on As(V) (A) but accumulate arsenic in the roots when grown on As(III) (B). Growth on arsenic-containing media caused an increase in superoxide dismutase (C) enzyme and peroxidase dismutase enzyme (D) activities in both the slim1–1 and slim1–2 mutants compared to WT controls.

Figure 3.. Thiol accumulation of slim1 mutants grown on arsenic.

Total shoot cysteine levels in slim1–1 and slim1–2 compared to WT (A). Total root cysteine levels in slim1–1 and slim1–2 compared to WT (B). Total shoot glutathione levels for slim1–1 and slim1–2 compared to WT (C). Total root glutathione levels for WT, slim1–1, and slim1–2 (D).

Figure 4.. Anion accumulation in slim1 mutants grown on arsenic.

Total shoot phosphate levels in slim1–1 and slim1–2 compared to WT (A). Total root phosphate levels in slim1–1 and slim1–2 compared to WT (B). Total shoot sulfate levels for slim1–1 and slim1–2 compared to WT (C). Total root sulfate levels for WT, slim1–1, and slim1–2 (D).