Transcriptome dynamics of a desert poplar (Populus pruinosa) in response to continuous salinity stress.

KEY MESSAGE: Using RNA sequencing analysis, we identified 9,216 regulatory and salt-related genes with differential expression and temporal expression trends which provide a clear picture of transcriptomic dynamics in response to continuous salinity stress in a desert poplar, Populus pruinosa. Populus pruinosa Schrenk is native to the desert region of western China and extraordinarily well adapted to the local salt stress. Thus, it is an ideal model for studying plants' adaptation to salt stress, but its transcriptomic responses have not been previously characterized. Thus, we analyzed time- courses of these responses via a series of sequencings. In total, we generated 157.4 million 100 bp paired-end clean reads and identified 9,216 differentially expressed genes (DEGs) between salt-stressed calli and controls. Gene ontology classification analysis revealed that salt stress-related categories--including 'oxidation reduction', 'transcription factor activity', 'membrane' and 'ion channel activity'--were highly enriched among these DEGs. In addition, we grouped the 9,216 DEGs by their expression dynamics into four clusters, and the genes in each cluster showed enrichment for particular functional categories. We also found that most DEGs were activated within 24 h of the stress and their expression stabilized after 48 h. All these findings suggest that gene expression rapidly and coordinately changes during this species' adaptation to salt stress. In addition, the identified DEGs provide critical genetic resources for further functional analyses and indications of potential transgenic modifications for developing salt-tolerant poplars.