More than half of the global population relies on rice as a staple food, but salinization
of soil presents a great threat to rice cultivation. Although previous studies have
addressed the possible benefits of arbuscular mycorrhizal (AM) symbiosis for rice
under salinity stress, the underlying molecular mechanisms are still unclear. In this
study, we found that mycorrhizal rice had better shoot and reproductive growth and
a significantly higher K + /Na + ratio in the shoot. The reactive oxygen species (ROS)
scavenging capacity in rice shoots was also improved by AM symbiosis. To elucidate
the molecular mechanisms required for AM-improved salt tolerance, transcriptome analysis
revealing the differentially expressed genes (DEGs) based on the response to AM symbiosis,
salinity or specific tissue was performed. Thirteen percent of DEGs showed tissue-preferred
responses to both AM symbiosis and salt stress and might be the key genes contributing
to AM-enhanced salt tolerance. Gene Ontology (GO) enrichment analysis identified GO
terms specifically appearing in this category, including cell wall, oxidoreductase
activity, reproduction and ester-related terms. Interestingly, GO terms related to
phosphate (Pi) homeostasis were also found, suggesting the possible role of the Pi-related
signaling pathway involved in AM-enhanced salt tolerance. Intriguingly, under nonsaline
conditions, AM symbiosis influenced the expression of these genes in a similar way
as salinity, especially in the shoots. Overall, our results indicate that AM symbiosis
may possibly use a multipronged approach to influence gene expression in a way similar
to salinity, and this modification could help plants be prepared for salt stress.
