Institute of Molecular Biology and Biotechnology, Bahauddin Zakariya University, Multan, Pakistan.
Department of Bioinformatics and Biotechnology, Government College University, Faisalabad, Pakistan.
Plant Signal Behav. 2024 Dec 31;19(1):2318513. doi: 10.1080/15592324.2024.2318513. Epub 2024 Mar 25.
Plant growth-promoting rhizobacteria (PGPRs) have been utilized to immobilize heavy metals, limiting their translocation in metal contaminated settings. However, studies on the mechanisms and interactions that elucidate how PGPRs mediate Nickel (Ni) tolerance in plants are rare. Thus, in this study we investigated how two pre-characterized heavy metal tolerant isolates of (ABT9 and ABT3) improve Ni stress tolerance in Arabidopsis while enhancing its growth and yield. Arabidopsis seedlings were grown for five weeks in control/Ni contaminated (control, 1.5 mM and 2.5 mM) potted soil, in the presence or absence of PGPRs. Plant growth characteristics, quantum yield, and antioxidative enzymatic activities were analyzed to assess the influence of PGPRs on plant physiology. Oxidative stress tolerance was quantified by measuring MDA accumulation in Arabidopsis plants. As expected, Ni stress substantially reduced plant growth (shoot and root fresh weight by 53.25% and 58.77%, dry weight by 49.80% and 57.41% and length by 47.16% and 64.63% over control), chlorophyll content and quantum yield (by 40.21% and 54.37% over control). It also increased MDA content by 84.28% at higher (2.5 mM) Ni concentrations. In contrast, inoculation with led to significant improvements in leaf chlorophyll, quantum yield, and Arabidopsis biomass production. The mitigation of adverse effects of Ni stress on biomass observed in -inoculated plants was attributed to the enhancement of antioxidative enzyme activities compared to Ni-treated plants. This upregulation of the antioxidative defense mechanism mitigated Ni-induced oxidative stress, leading to improved performance of the photosynthetic machinery, which, in turn, enhanced chlorophyll content and quantum yield. Understanding the underlying mechanisms of these tolerance-inducing processes will help to complete the picture of PGPRs-mediated defense signaling. Thus, it suggests that PGPRs candidate can potentially be utilized for plant growth promotion by reducing oxidative stress via upregulating antioxidant defense systems in Ni-contaminated soils and reducing Ni metal uptake.
植物促生根际细菌（PGPR）已被用于固定重金属，限制其在重金属污染环境中的迁移。然而，关于阐明 PGPR 如何介导植物对镍（Ni）耐受性的机制和相互作用的研究很少。因此，在这项研究中，我们研究了两种预先确定的耐重金属的 （ABT9 和 ABT3） 分离株如何在提高拟南芥 Ni 胁迫耐受性的同时促进其生长和产量。在有或没有 PGPR 的情况下，将拟南芥幼苗在对照/Ni 污染（对照，1.5 mM 和 2.5 mM）盆栽土壤中生长五周。分析植物生长特性、量子产量和抗氧化酶活性，以评估 PGPR 对植物生理学的影响。通过测量拟南芥植物 MDA 积累来量化氧化应激耐受性。正如预期的那样，Ni 胁迫极大地降低了植物的生长（地上部和根部鲜重分别减少了 53.25%和 58.77%，干重分别减少了 49.80%和 57.41%，长度分别减少了 47.16%和 64.63%）、叶绿素含量和量子产量（分别减少了 40.21%和 54.37%）。它还使 MDA 含量在较高（2.5 mM）Ni 浓度下增加了 84.28%。相比之下，接种 导致叶片叶绿素、量子产量和拟南芥生物量产量显著提高。与 Ni 处理植物相比，在 -接种植物中观察到减轻 Ni 胁迫对生物量的不利影响归因于抗氧化酶活性的增强。这种抗氧化防御机制的上调缓解了 Ni 诱导的氧化应激，从而提高了光合作用机构的性能，进而提高了叶绿素含量和量子产量。了解这些诱导耐受过程的潜在机制将有助于完成 PGPR 介导的防御信号的全貌。因此，这表明 候选 PGPR 可以通过在 Ni 污染土壤中通过上调抗氧化防御系统来减少氧化应激并减少 Ni 金属吸收，从而有可能通过促进植物生长来利用。
