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Soil salinization and cadmium (Cd) contamination severely inhibit crop production, and their coexistence is increasingly prevalent. Plant growth-promoting (PGP) bacteria (PGPB) have been proven to enhance crop resistance to single salinity or Cd stress. However, whether PGPB also play a positive role under combined salinity-Cd stress requires further investigation. In this study, we isolated a novel endophytic PGPB Pantoea sp. EEL5 (EEL5) from the leaves of Elytrigia elongata, an industrial crop with multiple abiotic stress tolerance traits. It exhibited multiple PGP traits (indole-3-acetic acid secretion, siderophore production, phosphate solubilization) and tolerance to salinity, Cd, drought, and acid. To our knowledge, this was the first report of PGPB isolation from this industrial crop. Pot experiments showed that EEL5 inoculation significantly promoted wheat seedlings growth under combined salinity-Cd stress, confirming its ability to improve wheat combined stress resistance. Transcriptomic analysis revealed that EEL5 inoculation upregulated most genes related to photosynthesis-antenna proteins, phenylpropanoid biosynthesis, glutathione metabolism, sulfur metabolism, and ion transport. These changes improved photosynthesis, boosted soluble sugar accumulation, reduced tissue Na + and Cd 2+ contents, enhanced reactive oxygen species (ROS) scavenging, and activated sulfur metabolism, collectively increasing stress resistance. Additionally, EEL5 increased soil enzyme activities and rhizosphere microbial diversity, especially by recruiting Bdellovibrio and Sphingomonas , which may represent another mechanism by which EEL5 alleviates combined stress. Overall, this work offers a theoretical foundation and practical strategy for developing bioinoculants to ensure safe and sustainable wheat production in Cd-contaminated saline soils. • An endophytic Pantoea sp. EEL5 was isolated from the leaves of Elytrigia elongata. • Pantoea sp. EEL5 possessed multiple PGP traits and abiotic stress resistance. • Pantoea sp. EEL5 improved wheat resistance to combined salinity-Cd stress. • EEL5 positively changed many gene expression in wheat under salinity-Cd stress. • EEL5 was beneficial to host rhizosphere microenvironment under salinity-Cd stress.
Yue et al. (Fri,) studied this question.