Comparative transcriptome analysis of Salix cupularis under drought stress

Abstract

Salix cupularis, an afforestation tree for soil and water conservation, is a deciduous willow species commonly cultivated in Sichuan Province, China. The research on the molecular mechanism of drought resistance of S. cupularis will contribute to the subsequent study of soil and water conservation, biodiversity, and ecological protection. Here, the results of an RNA-Seq analysis of transcriptomic data using Illumina deep sequencing technology to compare control (T1) and drought-stressed (T2) seedlings of S. cupularis were reported. Polyethylene glycol was used to induce drought stress in S. cupularis seedlings; 15-day-old seedlings were used for RNA-Seq analysis. De novo gene assembly was used to generate the comprehensive transcriptome, which was comprised of 65,228 unigenes, among which 16,192 were> 1 kb and accounted for 24.82% of the total unigene library. Analysis of the gene structure based on the unigene database, including open reading frame (ORF) predictions, simple sequence repeat (SSR) analysis, and inter-sample single nucleotide polymorphism (SNP) analysis, resulted in the identification of 758,779 SNP and 6779 SSR. After comparing the T1 and T2 gene profiles, 4289 differentially expressed genes (DEGs) were identified, of which 2340 were upregulated and 1949 were downregulated. The gene ontology (GO) analysis classified genes into the cellular component, molecular function, and biological process categories. The clusters of orthologous genes (COG) database was constructed based on the evolutionary phylogeny of bacteria, algae, and eukaryotes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of DEGs between T1 and T2 revealed that the top 20 enriched KEGG metabolic pathways were primarily in porphyrin and chlorophyll metabolism, photosynthesis, phenylpropanoid biosynthesis of phenylalanine metabolism, pentose and glucoronate interconversions, and glycan degradation, among other metabolic pathways. Collectively, these findings provide a theoretical basis for future studies on the genetic resistance of S. cupularis, and it also lay a foundation for the flow-up research of soil and water conservation, biodiversity, and ecological protection.