Transcriptome Profiling of Clematis apiifolia: Insights into Heat-Stress Responses.

Clematis apiifolia, belonging to the Clematis L., is a woody vine native to China. It is characterized as heat resistant and fast growing. To better understand potential mechanisms involved in heat-stress responses in Clematis, we characterized the digital gene expression signatures of C. apiifolia under heat-stress conditions. Using RNA sequencing technology, we sequenced six libraries, three biological replicates of control samples and three of heat-stressed samples. In total, 61,708 unigenes were obtained, 36,447 (59.06%) of which were annotated. There were 1941 differentially expressed genes (DEGs) under heat stress, including 867 upregulated and 1074 downregulated genes. Gene ontology enrichment of DEGs revealed that "metabolic process," "cellular process," and "single organism" were the top three functional terms under heat stress. A Kyoto Encyclopedia of Genes and Genomes analysis led to the identification of "protein processing in metabolic pathways," "phenylpropanoid biosynthesis," and "biosynthesis of secondary metabolites" as significantly enriched pathways. Among the upregulated genes, heat-shock factors and heat-shock proteins, especially small heat-shock proteins, were particularly abundant under heat stress. The data will aid in elucidating the molecular events underlying heat-stress responses in Clematis L.