SRO1 regulates heavy metal mercury stress response in Arabidopsis thaliana

Heavy metals in the environment are harmful limiting factors for the normal growth and development of plants. Here, we isolated and identified an Arabidopsis thaliana T-DNA insertion mutant, named sro1-1, which showed a hyper-sensitive response to HgCl₂. The SRO1 protein contains a WWE domain that mediates protein-protein interactions. Under HgCl₂ treatment, when compared with the wild-type plants, the growth of sro1-1 was repressed dramatically and the number of true leaves was reduced and etiolated. The electrolyte leakage rates showed that cell membrane integrity in sro1-1 was damaged more severely than in the wild type. DAB (3,5-diaminobenzidine) staining and confocal microscopy showed that Hg²⁺ stress induced more hydrogen peroxide accumulation in sro1-1 than in the wild type. The qRT-PCR results indicated that the expression of some abiotic stress-induced genes, such as L-ascorbate peroxidase (APX1), was reduced under oxidative or Hg²⁺ stress. Transgenic plants containing a GFP::SRO1 fusion protein showed that SRO1 was localized in the nucleus of the cells. SRO1 was shown to be expressed in various tissues, and was most highly expressed in the vigorous tissues. Our results suggest that SRO1 may play an important role in the stress response of A. thaliana to heavy metals.