Nitrate Transporter Gene Expression and Kinetics of Nitrate Uptake by Populus × canadensis ‘Neva’ in Relation to Arbuscular Mycorrhizal Fungi and Nitrogen Availability

Abstract

Plants and other organisms in the ecosystem compete for the limited nitrogen (N) in the soil. Formation of a symbiotic relationship with arbuscular mycorrhizal fungi (AMF) may influence plant competitiveness for N. However, the effects of AMF on plant nitrate (NO 3 − ) uptake capacity remain unknown. In this study, a pot experiment was conducted to investigate the effects of N application and Rhizophagus irregularis inoculation on the root absorbing area, uptake kinetics of NO 3 − , and the expression of NO 3 − transporter (NRT) genes in Populus × canadensis 'Neva'. The results showed that R. irregularis colonized more than 70% of the roots of the poplar and increased root active absorbing area/total absorbing area. The uptake kinetics of NO 3 − by poplar fitted the Michaelis-Menten equation. Mycorrhizal plants had a higher maximum uptake rate (V max ) value than non-mycorrhizal plants, indicating that R. irregularis enhanced the NO 3 − uptake capacity of poplar. The expression of NRTs in roots, namely, NRT1;2, NRT2;4B, NRT2;4C, NRT3;1A, NRT3;1B, and NRT3;1C, was decreased by R. irregularis under conditions of 0 and 1 mM NH 4 NO 3 . This study demonstrated that the improved NO 3 − uptake capacity by R. irregularis was not achieved by up-regulating the expression of NRTs in roots. The mycorrhizal pathway might repress root direct pathway in the NO 3 − uptake by mycorrhizal plants.

Arbuscular Mycorrhizal Symbiosis Differentially Affects the Nutritional Status of Two Durum Wheat Genotypes under Drought Conditions

“…Several previous studies have suggested that inoculation with AMF considerably improves the uptake of nitrogen and phosphorus in host plants [ 42 , 90 , 91 , 92 , 93 ]. In this study, mycorrhized Svevo plants accumulated considerably higher mineral nutrient leaf concentrations (SO 4 2− , NO 3 − , PO 4 3− , and Na + ) than the control Svevo plants under drought stress.…”

Morpho-physiology and Pht1 gene expressions in native maize plants with AM fungi and phosphorus

“…Studies have shown the benefits that AMF contribute to plants, mainly in promoting growth, productivity (Rocha et al, 2019;Scrase et al, 2019), and gene expressions related with P and N absorption, among others (Wu et al, 2020). When plants are colonized by AMF, they increase their capacity of exploring the soil surface and achieving crossing boundaries beyond the nutrient depletion zone, allowing them to absorb more water, macro and micronutrients (especially P, Zn, and Cu) that improve plant vigour (Liu et al, 2018).…”

“…Inorganic phosphate (Pi) is the chemical way that plants assimilate this macronutrient. Nonetheless, it shows low mobility and availability in soil due to its ion retention in soil particles charged positively (mineral oxides and clays) and/or to its precipitation in insoluble mineral complexes by its combination with calcium, iron and aluminum (Wu et al, 2020). Low Pi availability has turned out to be a limiting factor for agriculture production globally.…”

The Roles of Phosphorus and Nitrogen Nutrient Transporters in the Arbuscular Mycorrhizal Symbiosis

“…For N, the supply rate of N depends on the mineralization of organic N into inorganic N (NH 4 + or NO 3 − ) by microorganisms [ 122 ]. Determination of the 15 NO 3 − and 15 NH 4 + uptake rates indicated that AM fungi contributed more than the N uptake of the plants alone [ 123 ]. AM fungi maintains an extraradical mycelium that can extend several centimeters from the root.…”