Sequencing of Sitka spruce (Picea sitchensis) cDNA libraries constructed from autumn buds and foliage reveals autumn-specific spruce transcripts

Substantial efforts have been invested in recent years to characterize the expressed genome of major North American spruce species, namely Sitka spruce (Picea sitchensis), white spruce (Picea glauca) and interior spruce (Picea engelmanii x glauca). To date, more than 550,000 spruce expressed sequence tags (ESTs) have been publically deposited, most of which were constructed from various tissue collected during active primary growth. Here we report EST sequencing of dormant foliage and bud tissue collected from Sitka spruce. Both normalized and standard libraries were employed, with tissue collected at two autumn time points. A total of 30,681 ESTs were generated then assembled into 9,400 putative unique transcripts, or unigenes, with an average length of 779 bp. These autumn specific Sitka spruce ESTs were combined with autumn specific white spruce ESTs and compared with all spruce ESTs currently available. In total, 12,307 ESTs were unique to the autumn libraries, which assembled into 11,121 unigenes. Functional categorization suggests a role for some of these genes in bud dormancy and adaptation to freezing stress. Our results show that dormant tissue harbours a large number of transcripts not found in the same tissue during the growing season, and this sequence resource will therefore support ongoing studies of adaptive traits in spruce.