Inoculation with Arbuscular Mycorrhizal Fungi Reinforces Tea Plant’s Tolerance to Salinity

A major stress factor that can seriously limit plant growth and productivity is the soil degradation caused by salinity. Arbuscular mycorrhizal fungi (AMF) establish symbioses with most agricultural plants and improve growth under soil stress. In this study, tea plants with and without AMF inoculation under salt stress were investigated with the RNA-seq and the genome sequencing of tea plant, obtaining a positive insight into AMF-colonized involved in the improvement of growth and quality affected by lignin and cellulose synthesis under salt stress. Totals of 1402 and 1915 differentially expressed genes (DEGs) were identified in tea leaf with and without AMF under salt stress. Functional annotation analysis revealed that these DEGs were mainly involved in metabolic process, membrane and cell part and catalytic activity function. The Kyoto Encyclopedia of Genes and Genomes pathways analysis showed that the DEGs were enriched on the cellulose synthesis with AMF or enriched on the lignin and cellulose synthesis without AMF under salt stress. Further experiments verified that the more lignin deposited on the xylem vascular and the sclerenchyma of tea plants after salt stress, and lignin autofluorescence in tea plants with AMF was weaker than that without AMF. AMF inoculation could alleviate the salt stress, which showed in the decrease of lignin and cellulose accumulation. Moreover, the tea plants inoculated AMF increased tolerance by osmotic regulation and protective enzymes. In general, our results provide a more comprehensive insight into the role of AMF in adapting the adverse condition and keep the quality of fresh tea leaves in the northern Tea Area.