Transcriptomic analysis reveals the molecular mechanisms of arbuscular mycorrhizal fungi and nitrilotriacetic acid on Suaeda salsa tolerance to combined stress of cadmium and salt

Abstract

Halophytes are dominant plants in the phytoremediation of heavy metal contaminated saline soils. Arbuscular mycorrhizal (AM) fungi can improve plant abiotic stress tolerance and chelating agents nitrilotriacetic acid (NTA) can alleviate heavy metal stress. However, the combined effects and mechanisms of two amendments on halophytes grown in heavy metal contaminated saline soils are largely unknown. Pot experiment was conducted to explore the molecular mechanisms of Funneliformis mosseae (Fm) and NTA (10 mmol·kg−1) on Suaeda salsa tolerance to combined stress of Cd (5 mg·kg−1) and NaCl (2.5 g·kg−1). The results showed that AM fungi and NTA promoted growth of S. salsa, increased accumulations of Na+, Cd and mineral elements, but decreased Na+, Cd and malondialdehyde (MDA) concentrations in shoots under combined stress. Transcriptomic analysis presented various regulation pathways of the single or combined application of AM fungi and NTA on S. salsa. The identified differentially expressed genes (DEGs) in (Fm+NTA)/CK were mainly involved in antioxidant defense, osmoregulation, and photosynthesis; the DEGs in (Fm+NTA)/Fm were related to the maintenance of the cell membrane integrity and plant abiotic stress tolerance; and the DEGs in (Fm+NTA)/NTA were related to the enhancement ability of secondary cell wall synthesis and transcription factor. Our study provides new insights into the molecular mechanisms of AM fungi and NTA on halophytes tolerance to combined stress of heavy metal and salt.