The thiol-disulfide exchange activity of AtPDI1 is involved in the response to abiotic stresses

Background Arabidopsis protein disulfide isomerase 1 (AtPDI1) has been demonstrated to have disulfide isomerase activity and to be involved in the stress response. However, whether the anti-stress function is directly related to the activities of thiol-disulfide exchange remains to be elucidated. Results In the present study, encoding sequences of AtPDI1 of wild-type (WT) and double-cysteine-mutants were transformed into an AtPDI1 knockdown Arabidopsis line (pdi), and homozygous transgenic plants named pdi-AtPDI1, pdi-AtPDI1(m1) and pdi-AtPDI1(m2) were obtained. Compared with the WT and pdi-AtPDI1, the respective germination ratios of pdi-AtPDI1(m1) and pdi-AtPDI1(m2) were significantly lower under abiotic stresses and exogenous ABA treatment, whereas the highest germination rate was obtained with AtPDI1 overexpression in the WT (WT- AtPDI1). The root length among different lines was consistent with the germination rate; a higher germination rate was observed with a longer root length. When seedlings were treated with salt, drought, cold and high temperature stresses, pdi-AtPDI1(m1), pdi-AtPDI1(m2) and pdi displayed lower survival rates than WT and AtPDI1 overexpression plants. The transcriptional levels of ABA-responsive genes and genes encoding ROS-quenching enzymes were lower in pdi-AtPDI1(m1) and pdi-AtPDI1(m2) than in pdi-AtPDI1. Conclusion Taken together, these results clearly suggest that the anti-stress function of AtPDI1 is directly related to the activity of disulfide isomerase.

Automated summary

The study demonstrated that the anti-stress function of AtPDI1 in Arabidopsis is directly related to its disulfide isomerase activity. Mutant plants with altered cysteine residues showed significantly lower germination rates under stress conditions compared to wild-type and overexpressing lines. The transcriptional levels of stress-responsive genes were also lower in the mutant plants, indicating the importance of AtPDI1 in stress response.