Abstract
Rhazya stricta, Senna italica, and Zygophyllum simplex are important desert plants of Saudi Arabia with great economic and medicinal value. However, their tolerance and survival mechanisms under combined abiotic stresses such as high temperature, high salinity, and drought are not well understood. In order to investigate the potential molecule mechanism of abiotic stress tolerance in these plants, we used de novo transcriptome assembly and their comparative analysis. This study used leaf tissues to construct three cDNA libraries of these plants and then generated RNA-seq data by the Illumina HiSeq2000 platform. Sequencing reads were de novo assembled to generate: (a) 71,116 unigenes in R. stricta; (b) 59,274 unigenes in S. italica; (c) 70,300 unigenes in Z. simplex. Furthermore, the unigenes from these plants were annotated and analyzed with different databases. A comparative analysis of KEGG pathways identified several common pathways induced in these plants, including "Plant-pathogen interaction", "Plant hormone signal transduction", "Spliceosome", "RNA transport", and "Protein processing in endoplasmic reticulum", which may play an important role in combined abiotic drought, heat, and salinity stress. Finally, a comparative analysis of transcriptional regulators identified C2H2, C3H, CCHC(Zn), MYB-HB-like, PHD, WD40-like, and bHLH as common Transcription Factors responsible for abiotic stress tolerance in these plants. Our study revealed key factors involved in abiotic stress tolerance, which could be applied to develop high-yield transgenic crops capable of growing under combined abiotic stresses in the field.