Abstract
BackgroundWater shortage can limit plant growth, which can be ameliorated by arbuscular mycorrhizal (AM) symbiosis through physiological and metabolic regulations. Deciphering which physiological and metabolic processes are central for AM-mediated regulations is essential for applications of mycorrhizal biotechnology in dryland agriculture.MethodologyIn this study, the influence of AM symbiosis on growth performance, photosynthesis, and organ accumulation of key C and N metabolites were assessed by growing maize (Mo17, Lancaster Sure Crop) seedlings inoculated with or without AM fungus (Rhizophagus irregularis Schenck & Smith BGC AH01) under different water regimes in greenhouse.ResultsDrought stress reduced shoot growth, while AM symbiosis significantly improved growth performances, with significant changes of photochemical processes and organ concentration of the key metabolites. AM symbiosis increased root levels of the metabolites in ornithine cycle and unsaturation of fatty acids regardless of water conditions. Root putrescine (Put) concentration was higher in AM than non-inoculated (NM) plants under well-watered conditions; the conversion of Put via diamine oxidase to γ-aminobutyric acid (GABA) occurred in roots of AM plants under drought stress. Leaf concentration of Put, the tricarboxylic acids, and soluble sugars significantly increased in AM plants under drought stress, showing higher values compared to that of NM plants. Moreover, photosystem II efficiency and chlorophyll concentration were higher in AM than NM plants regardless of water status.ConclusionFatty acid- and ornithine cycle-related metabolites along with soluble sugars, Put, and GABA were the key metabolites of AM-mediated regulations in response to drought stress.
Highlights
Water shortage can limit plant growth, which can be ameliorated by arbuscular mycorrhizal (AM) symbiosis through physiological and metabolic regulations
AM colonization and plant growth Root colonization by R. irregularis was extensive in inoculated plants, with mycorrhizal colonization rate of about 60% under well-watered conditions, whereas root colonization was not detected in non-inoculated plants (Table 1)
Our results support the hypothesis that AM symbiosis significantly improved plant drought tolerance through altering ornithine cycle and fatty acid compositions in roots, and accumulation patterns of polyamines and carbohydrates in plant organs
Summary
Water shortage can limit plant growth, which can be ameliorated by arbuscular mycorrhizal (AM) symbiosis through physiological and metabolic regulations. Deciphering which physiological and metabolic processes are central for AM-mediated regulations is essential for applications of mycorrhizal biotechnology in dryland agriculture. Water deficit can cause plant physiological and metabolic disorders and limit plant growth. Soluble sugars (e.g., sucrose, glucose and fructose) have been demonstrated to increase in response to drought stress [2, 3]. Increased soluble sugars play important roles in stabilizing cell turgor pressure. These carbohydrates play roles in cellular respiration, cell homeostasis, and secondary metabolic processes [2]. Drought stress can induce changes of photoassimilate allocation between plant organs. Sucrose (Suc) is a main C form translocated from shoot sources to root sinks [4]
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