A transcriptomic approach to identify genes associated with wood density in Picea sitchensis

The demand for trees for industrial application is growing steadily and not expected to plateau for at least two decades; consequently, the supply of wood must increase to meet this need. One method for increasing yield without compromising land requirements is to modify wood density. The current study uses a transcriptomic approach to identify the genes associated with wood density that are likely to be of value in Sitka spruce (Picea sitchensis (Bong.) Carr.) breeding programmes. Following extensive wood density analysis from a Sitka field grown clonal trial, three detailed microarray studies were conducted to compare the transcriptome of cambium and xylem tissue from contrasting density clonal lines. Twenty-five genes exhibited differential expression, with up to 50-fold differences in expression observed, in at least two of the three microarray experiments, and this was verified using real-time polymerase chain reaction. Identified genes included those involved in cell wall synthesis, transcriptional regulation and plant pathogen defence functional categories. A wide range of processes influence wood density, but this study has identified potential regulators in these pathways. Future studies can now use this information to understand natural variation in wood density, and manipulate the expression of these genes to improve timber quality and yield.