Plant growth promoting rhizobacteria modulates the antioxidant defense and the expression of stress-responsive genes providing Pb accumulation and tolerance of grass pea

Abstract

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 signi cant positive effect of bacterial inoculation was reproduced in various parameters. Results indicated that inoculation of PGPR signi cantly increased the concentration of Pb by 20%, 66%, 43% and 36%, in roots and by 46%, 55%, 37%, 46% in shoots, respectively after 3, 6, 9 and 14 days of metal exposure as compared to the uninoculated plants. The metal accumulation in grass pea plants triggered a signi cant 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 at 6 and 9 d. Nevertheless, Pb treatment signi cantly increased oxidative stress and membrane damage in leaves with the highest hydrogen peroxide (H 2 O 2 ) production and tissue malondialdehyde (MDA) concentration recorded in uninoculated plants. Further, the inoculation alleviated the oxidative stress, improved plant tolerance and modulated the activities of antioxidant enzymes (SOD, CAT, APX, GR, DHAR and MDHAR). Similary, the expression patterns of LsPCS, LsGCN, LsCNGC, LsGR and LsGST through qRT-PCR demonstrated that bacterial inoculation signi cantly induced gene expression levels in leaves 6 d after Pb treatment, indicating that PGPR act as regulators of stress responsive genes.The ndings suggest the key role of PGPR (R. leguminosarum (M5) + Pseudomonas uorescens (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.

Epigenetic Control of Plant Response to Heavy Metals

“…As for genes related to the PTE-induced oxidative stress, inoculation with strains of Bacillus pumilus and Bacillus firmus improved the tolerance of Solanum tuberosum to Zn by enhancing the expression of a variety of ROS-scavenging enzymes (e.g., APX , SOD , CAT , DHAR , and GR ) [ 103 ]. Similar results were reported when inoculating Lathyrus sativus with a PGPB consortium prior to the application of excess Pb [ 104 ]. PGPBs can also increase the phytoextraction capacity by modulating the expression of specific genes in hyperaccumulator species.…”

Identification of Conserved Pathways in Bacillus Strains Known for Plant Growth-Promoting Behavior Using a Multifaceted Computational Approach

“…Various bacterial species, including Bacillus, Burkholderia, Azospirillum, Azotobacter, Rhizobium, and Pseudomonas, have been identified as PGPR, with Bacillus, Rhizobium, and Pseudomonas being the most prominent [2][3][4][5][6][7][8][9]. PGPR has been applied to a diverse range of plants, including chickpeas [10], maize [11], peas [12], peanuts [13], rice [14], soybeans [15], sugarcane, wheat [16], and sugarbeets [17]. Their positive impact on plant growth makes them valuable allies in sustainable agriculture practices.…”