Transcriptome analysis of Korean fir (Abies koreana) in response to elevated carbon dioxide and high temperature

Plants respond to combined stresses with different phenotypic and transcriptional changes from those in single-stress situations. Increasing temperature and carbon dioxide (CO2) concentration are key climate change factors that could affect plant growth and development, but the molecular mechanisms regulating responses to these factors are still poorly understood. To broadly survey genes with altered expression during combined CO2 and heat stresses, RNA samples were prepared from needles of Korean fir subjected to high CO2 and heat. RNA-sequencing analyses revealed that the expression of a large number of transcripts was altered under high temperature. Intriguingly, the transcriptomic results showed fewer gene expression changes under a combination of both high CO2 and temperature compared with heat treatment alone. Gene ontology analysis revealed the differentially expressed transcripts were mainly associated with metabolic process, binding and cell terms. The expression profiles of transcripts involved in metabolic pathways and cellular responses were identified using MapMan analysis, which revealed that CO2 and heat stresses induced transcript expression related to light reactions, biotic and abiotic stress responses, and development. Additionally, transcription factor genes known to be important for abiotic stress responses, such as ERF, bHLH, and NAC, were identified. The reliability of the observed expression patterns was confirmed by quantitative RT-PCR. The genetic knowledge acquired here will be useful for future studies of the molecular adaptation of this tree species to simultaneous environmental stresses.