De novo transcriptome assembly and analysis of Phragmites karka, an invasive halophyte, to study the mechanism of salinity stress tolerance

With the rapidly deteriorating environmental conditions, the development of stress tolerant plants has become a priority for sustaining agricultural productivity. Therefore, studying the process of stress tolerance in naturally tolerant species hold significant promise. Phragmites karka is an invasive plant species found abundantly in tropical and sub tropical regions, fresh water regions and brackish marshy areas, such as river banks and lake shores. The plant possesses the ability to adapt and survive under conditions of high salinity. We subjected P. karka seedlings to salt stress and carried out whole transcriptome profiling of leaf and root tissues. Assessing the global transcriptome changes under salt stress resulted in the identification of several genes that are differentially regulated under stress conditions in root and leaf tissue. A total of 161,403 unigenes were assembled and used as a reference for digital gene expression analysis. A number of key metabolic pathways were found to be over-represented. Digital gene expression analysis was validated using qRT-PCR. In addition, a number of different transcription factor families including WRKY, MYB, CCCH, NAC etc. were differentially expressed under salinity stress. Our data will facilitate further characterisation of genes involved in salinity stress tolerance in P. karka. The DEGs from our results are potential candidates for understanding and engineering abiotic stress tolerance in plants.