Genomic Scale Transcriptome And Expression Analysis Of Vascular Cambium In Poplar

Vascular cambium is an important tissue exists in forest trees different from herbaceous plant.Their activities produce new phloem and xylem outward an inward to make trees thicker. So thestudy on the vascular cambium can lead us to understand wood formation more. Vascularcambium arrests growth at the onset of winter in northern climates to prevent freezing-relateddamage. So, research the differently expressed genes in dormant and active cambium can helpus learning more about cold resistance and dehydration responses in the tissue. As importantmodel species for forest trees, Poplulus had been completed Genome Sequencing. In thisresearch, cryosectioning and laser microdissection was used to isolate vasc ular cambium cellsof poplar in active and dormant period. We analysis gene expression in vascular cambium ofdifferent period by using Affymetrix GeneChip array representing over56000poplar transcripts.The main results were as follows:376probes were considered to be up-regulated and674probes were down-regulated in activecambium. Whereas transcripts specific to2023probes were expressed only in active cambium,transcripts specific to433probes were expressed only in dormant cambium.Through the analysis of differentially expressed genes, we find that the stem cell regulationsystem may exist in vascular cambium, which similar to those in SAM and RAM. Importantgenes about cambium development such as WOX4, TDIF and TDR have signals in vasc ularcambium. And CLE12/13, CLE25expressed in vascular cambium too.Our data suggests that poplar vascular cambium may have regulatory networks that aresimilar to those that mediate responses to cold and dehydration stresses in Arabidopsis. Manygenes expressed at a lower level in active cambium than in dormant cambium have beenimplicated in cold-and dehydration-induced ABA-independent and dehydration-induced ABA-dependent pathways. The differential expression of DREB1A/CBF3and DREB1B/CBF1inactive and dormant vascular cambium suggests that cold-induced genes remain active duringthe early period of poplar growth in the spring, which may protect the tree from sudden cold.Several genes implicated in the cell cycle and DNA processing starting to express in activecambium indicated that high rates of mitosis, associated with considerable DNA replication andcell division, are characteristic of the early stages of activation of cambium. WOX4of poplar Nanlin95was successfully cloned. The expression of WOX4in differenttime and different tissues of poplar was detected by Real-time RT-PCR. The result showed thespecific expression of WOX4in secondary stems.Plant over-expression vectors for WOX4was constructed and used for Agrobacterium-mediated transformation of Arabidopsis thaliana.