Inoculation with abscisic acid (ABA)-catabolizing bacteria can improve phytoextraction of heavy metal in contaminated soil

Evolution of Abscisic Acid Signaling for Stress Responses to Toxic Metals and Metalloids

“…ABA-deficient Higher Cd concentration in the roots (Pompeu et al, 2017) induced by exogenously applied ABA or ABA-generating bacteria. The elevated IRT1 transcription was diminished in snrk2.2/2.3 mutant but further enhanced in the roots of ABAsensitive triple PP2Cs mutant abi1/hab1/abi2 lines, suggesting the involvement of AIT1, ABI5, SnRK2s, and PP2Cs in Cd absorption mediated by IRT1 (Fan et al, 2014;Xu et al, 2018;Pan et al, 2019;Zhang P. et al, 2019;Lu et al, 2020a). Additionally, ABI5 can be directly phosphorylated by SnRK2.2/2.3 and inactivated via dephosphorylation of ABI1/ HAB1/ABI2 (Fujii et al, 2009;Skubacz et al, 2016).…”

“…Application of low concentrations of ABA (0.1~1.0 mM) or inoculation with ABA-generating bacteria strains decreased Cd uptake through inhibiting transcription of IRT1 and thereby alleviating Cdinduced growth inhibition (Fan et al, 2014;Zhang P. et al, 2019;Pan et al, 2020). By contrast, an increase was observed in expression level of IRT1 and its homologous genes such as ZIP1 (Zinc Regulated Transporter/IRT-like Protein 1) and ZIP4 with Cd transporting-activity in the roots inoculated with ABAcatabolizing bacteria (Xu et al, 2018;Pan et al, 2019;Lu et al, 2020a). These positive effects were reduced in the ABA-Importing Transporter 1 (AIT1)-deficient mutant ait1 but enhanced in the AIT1-overexpressing transgenic plants (Pan et al, 2020).…”

“…ZEP, zeaxanthin epoxidase; NCEDs, 9-cisepoxycarotenoid dioxygenase; SDRs, short-chain alcohol dehydrogenase/reductases; AAOs, abscisic aldehyde oxidases; MOCOs, molybdenum cofactor sulfurase; BGLUs, b-glucosidases; ABCs, ATP-binding cassette transporters; NPFs, Nitrate Transporter 1/Peptide Transporter; DTXs, DTX/Multidrug and Toxic Compound Extrusion (MATE); bZIPs, Basic region/leucine zipper proteins; MYBs, MYB transcriptional factors; bHLHs, basic helix-loop-helix transcriptional factors; WRKYs, WRKY transcriptional factors; C 2 H 2 s, Cysteine-2/Histidine-2 type zinc-finger transcriptional factors; ZIPs, Zinc Regulated Transporter/Iron Regulated Transporter-like Proteins; HIPPs, Heavy metal-associated Isoprenylated Plant Proteins; PHTs, Phosphate transporters; NIPs, Nodulin 26-like Intrinsic membrane Proteins; GSHs, glutathione synthetases; PCSs, Phytochelatin synthetases. its homologs, ZIP1 and ZIP4 (Lu et al, 2020a). IRT1 is a member of the ZIP family with board substrates including iron (Fe), zinc (Zn), cobalt, manganese (Mn), and Cd (Rogers et al, 2000;Vert et al, 2002).…”

“…Moreover, in Cd-contaminated soil, greater biomass and lower Cd concentrations were determined in Arabidopsis and Brassica chinensis inoculated with ABA-generating bacteria, Azospirillum brasilense or Bacillus subtilis ( Xu et al, 2018 ; Pan et al, 2019 ). By contrast, decreasing the endogenous ABA amount by inoculation with an ABA-catabolizing bacteria, Rhodococcus qingshengii , significantly increased Cd content in Arabidopsis shoots by 47% ( Lu et al, 2020a ). Compared to the wild type, higher root Cd concentration was detected in ABA-deficient Slsit tomato mutant ( Table 1 ) ( Pompeu et al, 2017 ).…”

“…In addition, some members belonging to NRAMPs also transport free Cd ions ( Clemens and Ma, 2016 ; Zhang et al, 2018 ). For instance, the expression of HMA3 , Nramp1 , Nramp3 , and Nramp4 were upregulated in Arabidopsis incubation with ABA-catabolizing bacteria ( Lu et al, 2020a ), but overexpression of MhNCED3 in Arabidopsis inhibited the expression of IRT1 , Nramp1 , and HMA2 , leading to reduced Cd uptake and root-to-shoot translocation ( Zhang W. et al, 2019 ). Application of ABA promotes Cd resistance and mobility from root to shoot in the Cd-hyperaccumulating ecotype (HE) of Sedum alfredii by inducing the transcription of SaHMA2 , SaHMA3 , and SaHMA4 ( Lu et al, 2020b ).…”