Expression values from 6 time points during the regeneration of secondary vascular System (SVS)

Secondary vascular system (SVS) development resulted from cambial growth is a currently not well understood process. Therefore, more studies are needed to shed more lights on the molecular mechanisms underpinning the cambial activity. The regeneration of SVS from debarked trunk that can mimic the vascular cambium-driven wood formation has developed and could be used to revealed a larger number of differentially expressed genes during the stages of cambium formation and xylem differentiation in Populus tomentosa. We used microarrays to detail the global programme of gene expression in 6 time points during the regeneration of SVS. A 1-m strip of bark was peeled from 65 healthy P. tomentosa plants in a 4-year-old single clonal plantation (located in Tangshan, Hebei Province, China), starting 0.5 m from the tree base. Exposed tissue was wrapped with transparent plastic sheets to prevent desiccation. Samples were subsequently collected by scraping regenerating tissues from the whole surfaces of the trunks at the same daytime (between 10:00-11:00 am) at 7 days (D7), 10 days (D10), 12 days (D12), 16 days (D16), 18 days (D18), and 21 days (D21) after girdling (AG), and immediately frozen and stored in liquid nitrogen. Sampling was performed on three clonal trees at one time.