Physiological and differential gene expression reveals a trade‐off between antioxidant capacity and salt tolerance in halophytes Urochondra setulosa and Dichanthium annulatum

Abstract

Abstract Background Among abiotic stresses, soil salinity is one of the major global constraints to growth and productivity in most of the crop plants, limiting current and future agricultural sustainability. One of the strategies to dissect the salinity tolerance phenomenon can be the study of plants growing naturally in saline environments and halophytes can serve as another model plants for salt tolerance studies. Methods and Results Here, we studied two un-explored halophytes, moderately salt tolerant, Dichanthium annulatum and extremely salt tolerant, Urochondra setulosa for investigating the contributory role of antioxidative system, the first line of defence, in salinity tolerance mechanism at salinity levels of ECe ~ 30, 40 and 50 dSm− 1(~ 300,400,500 mM NaCl). H2O2 content, SOD and ascorbate peroxidase activities were higher in U. setulosa at all saline treatments whereas MDA content and catalase activity was high in D. annulatum although the specific enzyme activities of ROS system increased with increasing levels of salinity in both the halophytes. This differential physiological expression was in parallel with the transcriptomic data generated through High throughput sequencing on Illumina platform depicting 276 and 66 differentially expressed genes coding for various components of ROS system like antioxidant activity, cell redox and glutathione metabolism in response to salinity in U. setulosa and D. annulatum respectively. In D. annulatum, H2O2 is detoxified by increased activities of SOD, APX and catalase where as in halophyte U. setulosa, peroxidase takes over catalase to remove H2O2 along with DHAR and MDHAR which significantly correlates with the differentially expressed transcripts. Conclusions The salinity responsive gene expression for ROS enzymes and antioxidants clearly differentiate between these two halophytes supporting the detoxification of H2O2 and survival at different salinity levels. This study provides reference information on the key genes responsible for salt tolerance which can be used for related plant species for genetic improvement.