Vacuolar H+-ATPase (V-ATPase) is a vital protein complex involved in abiotic stress response in plants. The G subunit of Juglans regia (JrVHAG1) was previously identified as a drought tolerance-related gene involved in the ABA (abscisic acid)-signal pathway. Heavy metal stress is becoming a major detriment for plant growth, development, and production. In order to understand the role of JrVHAG1, the potential function mechanism of JrVHAG1 exposed to CdCl2 stress was confirmed in this study. Transcription of JrVHAG1 was induced by ABA and increased to 58.89-fold (roots) and 7.38-fold (leaves) and by CdCl2 to 2.65- (roots) and 11.42-fold (leaves) relative to control, respectively. Moreover, when treated simultaneously with ABA and CdCl2 (ABA+CdCl2), JrVHAG1 was up-regulated to 110.13- as well as 165.42-fold relative to control in the roots and leaves, accordingly. Compared to the wild type (WT) Arabidopsis plants, the transgenic plants with overexpression of JrVHAG1 (G2, G6, and G9) exhibited increased seed germination rate, biomass accumulation, proline content, and activities of superoxide dismutase (SOD) and peroxidase (POD) under ABA, CdCl2, and ABA+CdCl2 treatments. In contrast, the reactive oxygen species (ROS) staining, malondialdehyde (MDA) content, hydrogen dioxide (H2O2) content, as well as electrolyte leakage (EL) rates of transgenic seedlings were all lower than those of WT exposed to ABA, CdCl2 and ABA+CdCl2 stresses. Furthermore, a 1200 bp promoter fragment of JrVHAG1 was isolated by analyzing the genome of J. regia, in which the cis-elements were identified. This JrVHAG1 promoter fragment showed expression activity that was enhanced significantly when subjected to the above treatments. Yeast one-hybrid assay and transient expression analysis demonstrated that JrMYB2 specifically bound to the MYBCORE motif and shared similar expression patterns with JrVHAG1 under ABA, CdCl2 and ABA+CdCl2 stress conditions. Our results suggested that the JrVHAG1 gene functions as a CdCl2 stress response regulator by participating in ABA-signal pathway and MYB transcription regulation network. JrVHAG1 gene is a useful candidate gene for heavy metal stress tolerance in plant molecular breeding.

Our study navigated investigated the metal adsorption ability of bacterial Bacillus cereus strain HM-5 isolated from manganese ore. The effects of pH, initial metal ions concentration, biomass dose, contact time, and temperature on biosorption were studied. The results showed that the biosorption capacity of the B. cereus strain HM-5 for the metallic ions reached up to 98.9% for Mn at 600 mg/L initial metal ion concentration. The biosorptoin was most affected by pH and incubation temperature. Optimal pH and temperature were 6 and 35ºC, respectively. Optimal contact time was 5 d for biosorption by B. cereus strain HM-5. The surface chemical functional groups of B. cereus biomass identified by Fourier transform infrared (FTIR) were hydroxyl, alkyl, amide, phosphoryl, and phosphoric acid groups, which may be involved in the biosorption of heavy metals. SEM micrographs indicated that B. cereus HM-5 cells were irregular and cracked with the appearance of wrinkles and many flocs on the surface after Mn stress. The results showed that the selected bacteria had good application prospect in manganese-contaminated soil remediation.

GRAS transcription factor (TF) family is unique and numerous in higher plants with diverse functions that involving in plant growth and development processes, such as gibberellin (GA) signal transduction, root development, root nodule formation, and mycorrhiza formation. Walnut tree is exposed to various environmental stimulus that causing concern about its resistance mechanism. In order to understand the molecular mechanism of walnut to adversity response, a GRAS TF (JrGRAS2) was cloned and characterized from Juglans regia in this study. A 1500 bp promoter fragment of JrGRAS2 was identified from the genome of J. regia, in which the cis-elements were screened. This JrGRAS2 promoter displayed expression activity that was enhanced significantly by high temperature (HT) stress. Yeast one-hybrid assay, transient expression and chromatin immunoprecipitation (Chip)-PCR analysis revealed that JrDof3 could specifically bind to the DOFCOREZM motif and share similar expression patterns with JrGRAS2 under HT stress. The transcription of JrGRAS2 was induced by HT stress and up-regulated to 6.73-~11.96-fold in the leaf and 2.53-~4.50-fold in the root to control, respectively. JrGRAS2 was overexpressed in Arabidopsis, three lines with much high expression level of JrGRAS2 (S3, S7, and S8) were selected for HT stress tolerance analysis. Compared to the wild type (WT) Arabidopsis, S3, S7, and S8 exhibited enhanced seed germination rate, fresh weight accumulation, and activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and glutathione-S-transferase (GST) under HT stress. In contrast, the Evans blue staining, electrolyte leakage (EL) rates, hydrogen dioxide (H2O2) and malondialdehyde (MDA) content of transgenic seedlings were all lower than those of WT exposed to HT stress. Furthermore, the expression of heat shock proteins (HSPs) in S3, S7, and S8 was significant higher than those in WT plants. The similar results were obtained in JrGRAS2 transient overexpression walnut lines under normal and HT stress conditions. Our results suggested that JrDof3 TF contributes to improve the HT stress response of JrGRAS2, which could effectively control the expression of HSPs to enhance HT stress tolerance. JrGRAS2 is an useful candidate gene for heat response in plant molecular breeding.