Transcriptome analysis of Stipa purpurea interacted with endophytic Bacillus subtilis in response to temperature and ultraviolet stress

Stipa purpurea is a significant forage species on the Qinghai–Tibetan Plateau (QTP). Endophytic bacteria are the essential regulators for the growth, development, and tolerance of host plants. However, limited information is related to the molecular mechanisms of endophytic Bacillus subtilis- interacted S. purpurea in response to the adversity stress of QTP. High-throughput sequencing was conducted to compare the gene expression between B. subtilis -interacted (E) and B. subtilis -free (D) S. purpurea plants under high temperature, low temperature, and ultraviolet stress. The results indicated that a total of 125,103 Unigenes were assembled from 1,081,970,162 clean reads across all libraries, with 66,593 effectively annotated Unigenes (53.23%). Only one gene (Unigene0020366) described as jacalin-related lectin 1 was upregulated under high temperature, and 2 differentially expressed genes (DEGs) (Unigene0107370, Unigene0107567) were co-upregulated in the libraries of low temperature and ultraviolet radiation. In addition, DEGs from ultraviolet stress and low temperature libraries were primarily enriched in the metabolic process and ribosome, respectively. Furthermore, endophytic B. subtilis might function the ERF, C 2 H 2 , bHLH, GRAs and WRKY proteins of S. purpurea as key regulators in response to low temperature and ultraviolet radiation. The expression levels of 8 transcription factors verified through a qRT-PCR analysis were highly identical to the RNA-seq results. These results would provide molecular insight into the effect of endophytic B. subtilis on S. purpurea stress tolerance, as well as potential genetic engineering targets for enhancing abiotic stress in plant improvement.