De novo transcriptome sequencing and identification of genes related to salt and PEG stress in Tetraena mongolica Maxim

Key message The first transcriptome analyses of Tetraena mongolica provided 224,618 Unigenes and identified the genes that were differentially expressed under salt and drought conditions, giving some insights into the unique adaptive capacity of this relic plant. Tetraena mongolica Maxim, the only member of the Tetraena genus in the Zygophyllaceae, is endemic to the northwest of China. As one of the relic shrubs of the Paleo-Mediterranean flora, T. mongolica plays a key role in preserving the local ecological environment. To investigate its good adaptability in desert, we studied the transcriptome of T. mongolica under NaCl and PEG6000 stresses. Three libraries were constructed from a mixture of seedlings and mature plants of T. mongolica, and the de novo transcriptome was sequenced using an Illumina HiSeq 4000. Approximately 218.15 million clean reads were assembled de novo into 383,612 transcripts, and 116,027 All-Unigenes were identified. By aligning All-Unigene sequences against the NR database, we found that most of the All-Unigenes had very low matches with the sequences from other plants. A total of 21,112 SSRs and 6 types of SNP variants were identified. The RNA-Seq data revealed 60 transcription factor (TF) families with 3163 genes in total. Six libraries were constructed from the separate control or stressed seedlings, and the transcriptome was sequenced using a BGISEQ-500 platform. There are 1105 and 1383 differentially expressed genes (DEGs) with 42 and 54 TFs under NaCl and PEG6000 treatment, respectively. The genes that were putatively involved in salt and osmotic stresses were searched and analyzed. Quantitative reverse transcription PCR (qRT-PCR) showed that DEG expression profiles were consistent with those from RNA-seq (RNA sequencing). Overall, this study provides new insights into the molecular mechanisms that control salt and drought stress responses in T. mongolica.