Effect of Serendipita indica on gene expression in Arabidopsis thaliana seedlings under control and salt stress conditions

Serendipita indica, a widely studied beneficial root fungal endophyte, promotes plant growth under saline conditions by reducing Na? accumulation in host plants, including Arabidopsis thaliana. This reduction in Na? levels likely contribute to salt detoxification, though the underlying mechanisms remain unclear. Previous studies have demonstrated that SOS1, a key Na+ transporter and major determinant of salt tolerance in plants, is not involved in this reduction. To explore whether other plant transporters might participate in Na+ reduction, we first characterized the full Arabidopsis transportome, with putative substrates and subcellular localizations, and performed a comprehensive transcriptomic analysis of the full set of transporter proteins. In this study, we investigated and ruled out the possible contribution of HKT1, another relevant Na+ transporter implicated in salt adaptation in Arabidopsis. By examining differentially expressed transporters under salt stress, we identified a subset of candidate genes potentially involved in Na? transport. Among these, we evaluated the role of CNGC10 and CNGC13 using mutant lines under both S. indica- and non-colonized conditions. Interestingly, both transporters appeared to be involved in the endophyte-induced decrease in Na? accumulation although, other, yet-unidentified transporters may also contribute to this phenomenon, warranting further functional investigation of the candidate genes highlighted in our analysis. Overall design: RNA-seq profiling of wild-type Columbia-0 Arabidopsis thaliana seedlings inoculated or non-inoculated with Serendipita indica in salt stress (50 mM NaCl) or control conditions (0 mM NaCl).