Arbuscular mycorrhizal symbioses alleviating salt stress in maize is associated with a decline in root-to-leaf gradient of Na + /K + ratio

• Published in: BMC plant biology Vol. 21; no. 1; p. 457
• Main Authors: Wang, Hao, An, Tingting, Huang, Di, Liu, Runjin, Xu, Bingcheng, Zhang, Suiqi, Deng, Xiping, Siddique, Kadambot H M, Chen, Yinglong
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 07.10.2021; BioMed Central; BMC
• Subjects: Abiotic stress; Arbuscular mycorrhizal fungi; Arbuscular mycorrhizas; Chloroplast; Chloroplasts; Compartmentation; Corn; Efflux; Fungi; Fungi - physiology; Gene expression; Gene regulation; Genes; Genetic aspects; Genetic Variation; Genotype; Genotype & phenotype; Genotypes; Hardiness; Host plants; Inoculation; Ion balance; Ion Transport - physiology; Maize; Mesophyll; Morphology; Mycorrhizae - physiology; Mycorrhizas; Physiological aspects; Plant growth; Plant Roots - chemistry; Plant Roots - metabolism; Plant Shoots - chemistry; Plant Shoots - metabolism; Plant tissues; Plants; Potassium - analysis; Potassium - metabolism; Potassium channels; Roots; Roots (Botany); Salinity; Salinity tolerance; Salt; Salt stress (Botany); Salt Stress - physiology; Salt tolerance; Salt Tolerance - physiology; Shoots; Sodium - analysis; Sodium - metabolism; Sodium channels; Sodium chloride; Soil amendment; Structure-function relationships; Symbiosis; Symbiosis - physiology; Toxicity; Translocation; Ultrastructure; Zea mays - genetics; Zea mays - metabolism; Zea mays - microbiology; China; Ion balance; Salt tolerance; Maize; Arbuscular mycorrhizal fungi; Chloroplast
• ISSN: 1471-2229; 1471-2229
• DOI: 10.1186/s12870-021-03237-6

Inoculation of arbuscular mycorrhizal (AM) fungi has the potential to alleviate salt stress in host plants through the mitigation of ionic imbalance. However, inoculation effects vary, and the underlying mechanisms remain unclear. Two maize genotypes (JD52, salt-tolerant with large root system, and FSY1, salt-sensitive with small root system) inoculated with or without AM fungus Funneliformis mosseae were grown in pots containing soil amended with 0 or 100 mM NaCl (incrementally added 32 days after sowing, DAS) in a greenhouse. Plants were assessed 59 DAS for plant growth, tissue Na and K contents, the expression of plant transporter genes responsible for Na and/or K uptake, translocation or compartmentation, and chloroplast ultrastructure alterations. Under 100 mM NaCl, AM plants of both genotypes grew better with denser root systems than non-AM plants. Relative to non-AM plants, the accumulation of Na and K was decreased in AM plant shoots but increased in AM roots with a decrease in the shoot: root Na ratio particularly in FSY1, accompanied by differential regulation of ion transporter genes (i.e., ZmSOS1, ZmHKT1, and ZmNHX). This induced a relatively higher Na efflux (recirculating) rate than K in AM shoots while the converse outcoming (higher Na influx rate than K ) in AM roots. The higher K : Na ratio in AM shoots contributed to the maintenance of structural and functional integrity of chloroplasts in mesophyll cells. AM symbiosis improved maize salt tolerance by accelerating Na shoot-to-root translocation rate and mediating Na /K distribution between shoots and roots.