Potential of Rhizobia Nodulating Anthyllis vulneraria L. from Ultramafic Soil as Plant Growth Promoting Bacteria Alleviating Nickel Stress in Arabidopsis thaliana L.

Abstract

Rhizobia, which enter into symbiosis with legumes, can also interact with non-legumes and promote plant growth. In this paper, we explored the effects of nickel (Ni, 200 µM) on Arabidopsis thaliana (Col-0) inoculated with plant growth-promoting (PGP) rhizobia nodulating ultramafic Anthyllis vulneraria. The isolated PGP strains tolerant to Ni were identified as Rhizobium sp. and Bradyrhizobium sp. The isolates highly differed in their PGP abilities and Ni resistance. Without Ni-stress, the plants inoculated with most isolates grew better and had higher photosynthetic efficiency than non-inoculated controls. Nickel treatment increased Ni concentration in inoculated plants. Plant growth, leaf anatomy, chloroplast ultrastructure, efficiency of photosynthesis, and antioxidant defense system activity were significantly impaired by Ni, however, the majority of these effects were diminished in plants inoculated with the most effective PGP rhizobia. Real-time PCR revealed an increased expression level of genes involved in auxin and gibberellin biosynthesis in the inoculated, Ni-treated plants, and this may have improved shoot and root growth after inoculation with effective isolates. Our results also suggest a positive correlation between Ni-stress parameters and antioxidant defense system activity, and also between the effectiveness of photosynthesis and plant growth parameters. We showed that the selected rhizobia, naturally nodulating Anthyllis on Ni-rich ultramafic soils can promote Arabidopsis growth and increase plant tolerance to Ni by improving different physiological and biochemical mechanisms.

Inducing Rhizosphere Acidification in White Willow with Bacillus sp. ZV6 Enhances Ni Phytoextraction from Soil and Soil Quality

“…•− generation rate, respectively, compared to the control. Reduced activity of APX, SOD, and CAT and an elevated H 2 O 2 content was observed in Arabidopsis thaliana in Ni-polluted soil [59]. In another study, Valivand et al [54] reported that Ni-polluted soil reduced antioxidant enzyme activities (CAT and POD) and increased the contents of H 2 O 2 and MDA in the zucchini plant.…”

“…Nickel reduces plant growth and yield by reducing the absorption of nutrients by the roots, damaging thylakoid structures, lowering ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) activity, and affecting stomatal closure and the biosynthesis of chlorophyll [57,58]. Interestingly, adding PGPR to Ni-polluted soil notably boosted the growth and the DW of Arabidopsis thaliana L. [59]. The contents of phenolic compounds in wheat [56], while that of protein and carotenoid in Zea mays [60] were boosted in the presence of Bacillus sp.…”