Transcriptomic responses governing heartwood formation and osmotic stress responses in western redcedar (Thuja plicata)

Thuja plicata trees produce a heartwood that is well known for its durability; nevertheless, logged trees are frequently afflicted by heartwood rot. In addition, increasingly severe summer droughts are resulting in T. plicata die-off in coastal British Columbia. The genetic bases of heartwood formation and drought resistance in T. plicata are unknown. To generate a comprehensive overview of the activities during heartwood formation and exposure to drought, transcriptome profiling was done. Heartwood formation indicated expected processes such as terpene and lignan biosynthesis, but also unexpected activities, most notably flavonoid and wax biosynthesis, hormone signaling and transcription regulators, providing new targets for rot resistance selection. Similar comparisons of the effect of drought stress on roots and stems identified hundreds of genes, many of which mapped to known functions in drought resistance and allowed, for the first time, the formulation of a framework for how T. plicata responds to drought stress.