A transcriptional roadmap to wood formation

The large vascular meristem of poplar trees with its highly organized secon dary xylem enables the boundaries between different developmental zones to be easily distinguished. This property of wood-forming tissues allowed us t o determine a unique tissue-specific transcript profile for a well defined developmental gradient. RNA was prepared from different developmental stage s of xylogenesis for DNA microarray analysis by using a hybrid aspen unigen e set consisting of 2,995 expressed sequence tags. The analysis revealed th at the genes encoding lignin and cellulose biosynthetic enzymes, as well as a number of transcription factors and other potential regulators of xyloge nesis, are under strict developmental stage-specific transcriptional regula tion.