Arbuscular Mycorrhizae Mitigate Aluminum Toxicity and Regulate Proline Metabolism in Plants Grown in Acidic Soil

Abstract

Arbuscular mycorrhizal fungi (AMF) can promote plant growth and induce stress tolerance. Proline is reported to accumulate in mycorrhizal plants under stressful conditions, such as aluminum (Al) stress. However, the detailed changes induced in proline metabolism under AMF–plant symbiosis has not been studied. Accordingly, this work aimed to study how Al-stressed grass (barley) and legume (lotus) species respond to AMF inoculation at growth and biochemical levels. The associated changes in Al uptake and accumulation, the rate of photosynthesis, and the key enzymes and metabolites involved in proline biosynthesis and degradation pathways were studied. Soil contamination with Al induced Al accumulation in tissues of both species and, consequently, reduced plant growth and the rate of photosynthesis, while more tolerance was noticed in lotus. Inoculation with AMF significantly reduced Al accumulation and mitigated the negative impacts of Al on growth and photosynthesis in both species; however, these positive effects were more pronounced in barley plants. The mitigating action of AMF was associated with upregulation of proline biosynthesis through glutamate and ornithine pathways, more in lotus than in barley, and repression of its catabolism. The increased proline level in lotus was consistent with improved N metabolism (N level and nitrate reductase). Overall, this study suggests the role of AMF in mitigating Al stress, where regulation of proline metabolism is a worthy mechanism underlying this mitigating action.

Effect of High-Temperature Stress on Plant Physiological Traits and Mycorrhizal Symbiosis in Maize Plants

“…Previously, Hussain et al [11] have reported that AMF coating on seeds enhanced root colonization in maize plants. AMF not only improves colonization and protects plants under high-temperature stress as shown in the present study but also mitigated the impact of Al toxicity in lotus and barley plants by accumulating Al in roots and ultimately protecting the plants from metal stress as well [14]. Root colonization helped in the upregulation of photosynthetic rate in AMF and AMF + HT plants.…”

“…Various studies have reported that AMF improved stress mitigation and tolerance in plants [11,13,14,23,42,43]. AMF increases plant growth by improving nutrition acquisition, root architecture, and increasing antioxidant activity, as well as stress tolerance [44][45][46].…”

“…AMF augments plant stress tolerance by increasing nutrient levels, improving stomatal regulation, water use efficiency to reduce oxidative damage, modifying hormonal balance and osmotic adjustments [9][10][11]. The inoculation with AMF enables host plants to cope up with stressful conditions such as salinity, drought, and heavy metals [12][13][14].…”

Arbuscular Mycorrhizal Fungi and Endophytic Fungi Activate Leaf Antioxidant Defense System of Lane Late Navel Orange

“…One the most important characteristics of this AM symbiosis is to help the host absorb nutrients and water that cannot be reached by the root, to enhance the resistance of the host plant to abiotic stress [ 11 , 12 ]. The AM symbiosis between AM fungi and host plants enhances the resistance of host plants to drought, salt stress, high temperature, nutrient stress, aluminum toxicity, and waterlogging stress by affecting their antioxidant enzyme defense systems [ 13 , 14 , 15 , 16 ]. Zhang et al [ 17 ] observed an induced expression of superoxide dismutase ( SOD ) and catalase ( CAT ) genes in roots of trifoliate orange ( Poncirus trifoliata L.…”

Lepidium sativum Sprouts Grown under Elevated CO2 Hyperaccumulate Glucosinolates and Antioxidants and Exhibit Enhanced Biological and Reduced Antinutritional Properties

“…Amino acids were determined from 200 mg of sprouts combined with 1 mL of 80% (v/v) aqueous ethanol [24]. For accurate evaluation and correction of varied mass spectrometry reactions, norvaline was employed as an internal standard.…”