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Transcriptional switches controlling wood cell fates<br />
S3.2<br />
MISATO OHTANI 1,2 , BO XU 2 , MASATOSHI YAMAGUCHI 3 , 11:30–12.00<br />
MINORU KUBO 2 , TAKU DEMURA 1,2<br />
demura@bs.naist.jp<br />
1 Graduate School of Biological Sciences, Nara Institute of Science and<br />
Technology, Ikoma, Nara, Japan; 2 RIKEN Center for Sustainable Resource<br />
Science, Yokohama, Kanagawa, Japan; 3 Institute for Environmental<br />
Science and Technology, Saitama University, Saitama, Japan; 4 Center for<br />
Frontier Science and Technology, Nara Institute of Science and<br />
Technology, Ikoma, Nara, Japan<br />
Wood has long been used for natural materials including pulp, timber, and wood products. Recently,<br />
in addition, wood is also expected to be utilized as a sustainable and carbon-neutral resource for<br />
bioenergy. Therefore, it is important to understand the process of wood formation for improving the<br />
quality and quantity of wood and wood product. Hard wood contains two major cell types, fiber and<br />
vessel, which have similar but distinct developmental processes. Recent considerable effort has<br />
identified the regulatory genes for the differentiation of each cell type. Using Arabidopsis, we<br />
showed that VASCULAR-RELATED NAC-DOMAIN6 (AtVND6) and AtVND7 are the transcriptional<br />
switches for metaxylem and protoxylem vessels, respectively: overexpression of AtVND6 and<br />
AtVND7 can induce the transdifferentiation of various types of cells into metaxylem and protoxylem<br />
vessels, respectively, not only in Arabidopsis but also heterologously in poplar. Further researches<br />
revealed that two genes (AtNST1 and AtNST3/SND1) belonging to the same gene family of AtVND6<br />
and AtVND7 are the key regulators of fiber differentiation in Arabidopsis. Based on the phylogenetic<br />
analysis, we also showed that 16 poplar genes (PtVNS1 to PtVNS16, of which 12 genes also called<br />
PtrWND1A to PtrWND6B) were homologous to the VND and NST/SND genes. Moreover, the<br />
functional analysis of these genes suggested that wood formation in poplar is regulated by the<br />
cooperative functions of the PtVNS/PtrWND genes.<br />
These transcriptional switches seem to be conserved in evolutionary history. We recently revealed<br />
that the differentiation of water-conducting and supporting cells in moss Physcomitrella patens,<br />
hydroid and stereid cells, respectively, is regulated by genes (PpVNS1 to PpVNS8) homologous to the<br />
VND/NST/SND genes. Concomitant loss of function of PpVNS1, 6, and 7 failed to form normal<br />
hydroid and stereid cells, suggesting conservation of the transcriptional between Arabidopsis and<br />
moss.<br />
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