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

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. Halophytes are the most suitable host plants to dissect the salinity tolerance phenomenon in natural environment. To elucidate the mechanisms of salinity tolerance is an ever growing research area for genetic engineering of crops to improve the salinity tolerance and ultimately to improve the crop yield and quality. Methods and results In the present investigation, two un-explored halophytes, i.e. moderately salt tolerant ( Dichanthium annulatum ) and extremely salt tolerant ( Urochondra setulosa) were studied for unrevealing the contributory role of antioxidative system in salinity tolerance at higher saline intensities of EC e ~30, 40 and 50dSm − 1 . Experimental findings indicated that the accumulation of hydrogen peroxide (H 2 O 2 ) content, Superoxide dismutase (SOD) and ascorbate peroxidase (APX) activities were higher in U. setulosa at all saline treatments. Whereas, higher order of malondialdehyde (MDA) content and catalase (CAT) activity was observed in D. annulatum , although the specific enzyme activities of chemically reactive oxygen species (ROS) system increased with increasing levels of salinity in both the halophytes. This differential physiological mechanism was collaborated with the transcriptomic data generated through High throughput sequencing on Illumina platform. Transcriptome expression analysis depicting that a total of 276 and 66 genes coding for various components of ROS system like antioxidant activity, cell redox and glutathione metabolism were differentially expressed in response to salinity stress in U. setulosa and D. annulatum , respectively. Biochemical analysis indicated that H 2 O 2 is detoxified by increased activities of SOD, APX and CAT in D. annulatum , however, in U. setulosa , POX takes over catalase to remove the higher accumulation of H 2 O 2 along with dehydroascorbate reductase (DHAR) and monodehydroascorbate reductase (MDHAR) significantly associated with the differentially expressed transcripts. Conclusions The differentially expressed genes for ROS enzymes and antioxidants clearly differentiate and support the detoxification of H 2 O 2 and survival mechanism of Urochondra setulosa and Dichanthium annulatum at different salinity levels. This study provides the reference information for key regulatory genes responsible for salinity stress tolerance and can be used for increasing salinity tolerance of related crop species.