Abdelkrim Souhir, Abid Ghassen, Chaieb Oumaima, Taamalli Wael, Mannai Khediri, Louati Faten, Jebara Moez, Jebara Salwa Harzalli
Laboratory of Legumes and Sustainable Agro-systems, Center of Biotechnology of Borj Cedria, BP 901, 2050, Hammam Lif, Tunisia.
National Agronomic Institute of Tunisia, University of Carthage, Tunis, Tunisia.
Environ Sci Pollut Res Int. 2023 Jan;30(4):10789-10802. doi: 10.1007/s11356-022-22874-4. Epub 2022 Sep 9.
To ensure the success of phytoremediation, it is important to consider the appropriate combination of plants and microorganisms. This study was conducted to get a better insight into the underlying molecular and biochemical mechanism of grass pea (Lathyrus sativus L.) induced by plant growth promoting rhizobacteria (PGPR), when exposed for 3, 6, 9, and 14 days to 1 mM Pb in a hydroponic system. The significant positive effect of bacterial inoculation was reproduced in various parameters. Results indicated that inoculation of PGPR significantly increased the accumulation of Pb by 20%, 66%, 43%, and 36% in roots and by 46%, 55%, 37%, and 46% in shoots, respectively after 3, 6, 9, and 14 days of metal exposure compared to the uninoculated plants. The metal accumulation in grass pea plants triggered a significant elevation in the synthesis of non-protein thiols (NPT), particularly in inoculated plant leaves where it was about 3 and 2-fold higher than the uninoculated set on the 6 and the 9 day. Nevertheless, Pb treatment significantly increased oxidative stress and membrane damage in leaves with the highest hydrogen peroxide (HO) production and tissue malondialdehyde (MDA) concentration recorded in uninoculated plants. Furthermore, the PGPR inoculation alleviated the oxidative stress, improved significantly plant tolerance, and modulated the activities of antioxidant enzymes (SOD, CAT, APX, GR, DHAR, and MDHAR). Similarly, the expression patterns of LsPCS, LsGCN, LsCNGC, LsGR, and LsGST through qRT-PCR demonstrated that bacterial inoculation significantly induced gene expression levels in leaves 6 days after Pb treatment, indicating that PGPR act as regulators of stress-responsive genes. The findings suggest the key role of PGPR (R. leguminosarum (M5) + Pseudomonas fluorescens (K23) + Luteibacter sp. + Variovorax sp.) in enhancing Pb accumulation, reducing metal toxicity, strengthening of the antioxidant system, and conferring higher Pb tolerance to grass pea plants. Hence, the association Lathyrus sativus-PGPR is an effective tool to achieve the goal of remediation of Pb contaminated sites.
为确保植物修复的成功，考虑植物与微生物的适当组合很重要。本研究旨在更深入了解在水培系统中，当鹰嘴豆（草香豌豆，Lathyrus sativus L.）暴露于1 mM铅3天、6天、9天和14天时，植物促生根际细菌（PGPR）诱导的潜在分子和生化机制。细菌接种在各种参数上都产生了显著的积极影响。结果表明，与未接种的植物相比，在金属暴露3天、6天、9天和14天后，接种PGPR分别使根部铅积累显著增加20%、66%、43%和36%，地上部铅积累分别增加46%、55%、37%和46%。鹰嘴豆植株中的金属积累引发了非蛋白硫醇（NPT）合成的显著升高，特别是在接种植物的叶片中，在第6天和第9天，其含量比未接种组分别高出约3倍和2倍。然而，铅处理显著增加了叶片中的氧化应激和膜损伤，未接种植物中过氧化氢（HO）产量和组织丙二醛（MDA）浓度最高。此外，PGPR接种减轻了氧化应激，显著提高了植物耐受性，并调节了抗氧化酶（超氧化物歧化酶、过氧化氢酶、抗坏血酸过氧化物酶、谷胱甘肽还原酶、脱氢抗坏血酸还原酶和单脱氢抗坏血酸还原酶）的活性。同样，通过qRT-PCR对LsPCS、LsGCN、LsCNGC、LsGR和LsGST的表达模式分析表明，铅处理6天后，细菌接种显著诱导了叶片中的基因表达水平，表明PGPR作为应激反应基因的调节因子发挥作用。研究结果表明PGPR（豆科根瘤菌（M5）+荧光假单胞菌（K23）+黄杆菌属+贪铜菌属）在增强铅积累、降低金属毒性、强化抗氧化系统以及赋予鹰嘴豆植株更高的铅耐受性方面发挥关键作用。因此，鹰嘴豆-PGPR组合是实现铅污染场地修复目标的有效工具。
