Plant metallothioneins (MTs) are a family of low molecular weight, cysteine-rich, and metal-binding proteins, which play an important role in the detoxification of heavy metal ions, osmotic stresses, and hormone treatment. Sequence analysis revealed that the open-reading frame (ORF) of ZjMT was 225 bp, which encodes a protein composed of 75 amino acid residues with a calculated molecular mass of 7.376 kDa and a predicated isoelectric point (pI) of 4.83. ZjMT belongs to the type I MT, which consists of two highly conserved cysteine-rich terminal domains linked by a cysteine free region. Our studies showed that ZjMT was primarily localized in the cytoplasm and the nucleus of cells and ZjMT expression was up-regulated by NaCl, CdCl₂ and polyethylene glycol (PEG) treatments. Constitutive expression of ZjMT in wild type Arabidopsis plants enhanced their tolerance to NaCl stress during the germination stage. Compared with the wild type, transgenic plants accumulate more Cd²⁺ in root, but less in leaf, suggesting that ZjMT may have a function in Cd²⁺ retension in roots and, therefore, decrease the toxicity of Cd²⁺.

The aim of this study was to explore the beneficial effects of endophytic Pseudomonas poae strain S61 on medicinal plant Astragalus mongholicus. Growth and production of indoleacetic acid (IAA) of the strain was firstly characterized under stress conditions, demonstrating that the strain performance was more robust in the medium containing 20% PEG6000. Beneficial effects of the strain on host seedlings were then investigated by pouring 20% PEG6000 for 3 weeks to mimic drought stress. Among growth parameters, root biomass and root-shoot ratio were significantly enhanced by the combination of 20% PEG6000 with the strain inoculation while the individual trial had no effect. The combination trial also increased calycosin-7-O-glucoside and ononin accumulations in the roots, suggesting that the strain executed beneficial effects on A. mongholicus only when it grew under drought stress. Using MDA as lipid peroxidation parameter, our result indicated that leaf lipid peroxidation should be involved in the process.