Yamaguchi Masatoshi, Kubo Minoru, Fukuda Hiroo, Demura Taku
Plant Science Center, RIKEN, Yokohama, Kanagawa 230-0045, Japan.
Plant J. 2008 Aug;55(4):652-64. doi: 10.1111/j.1365-313X.2008.03533.x. Epub 2008 Apr 24.
The Arabidopsis thaliana NAC domain transcription factor, vascular-related NAC-DOMAIN7 (VND7), plays a pivotal role in regulating the differentiation of root protoxylem vessels. In order to understand the mechanisms underscoring the function of VND7 in vessel differentiation in more detail, we conducted extensive molecular analyses in yeast (Saccharomyces cerevisiae), Arabidopsis, and Nicotiana tabacum L. cv. Bright Yellow 2 (tobacco BY-2) cells. The transcriptional activation activity of VND7 was confirmed in yeast and Arabidopsis, and the C-terminal region was shown to be required for VND7 transcriptional activation. Expression of the C-terminus-truncated VND7 protein under the control of the native VND7 promoter resulted in inhibition of the normal development of metaxylem vessels in roots and vessels in aerial organs, as well as protoxylem vessels in roots. The expression pattern of VND7 overlapped that of VND2 to VND5 in most of the differentiating vessels. Furthermore, a yeast two-hybrid assay revealed the ability of VND7 to form homodimers and heterodimers with other VND proteins via their N-termini, which include the NAC domain. The heterologous expression of VND7 in tobacco BY-2 cells demonstrated that the stability of VND7 could be regulated by proteasome-mediated degradation. Together these data suggest that VND7 regulates the differentiation of all types of vessels in roots and shoots, possibly in cooperation with VND2 to VND5 and other regulatory proteins.
拟南芥NAC结构域转录因子——维管相关NAC结构域7（VND7），在调节根原生木质部导管的分化过程中起关键作用。为了更详细地了解VND7在导管分化中发挥功能的潜在机制，我们在酵母（酿酒酵母）、拟南芥和烟草（烟草品种Bright Yellow 2，即烟草BY-2）细胞中进行了广泛的分子分析。VND7的转录激活活性在酵母和拟南芥中得到证实，并且其C末端区域被证明是VND7转录激活所必需的。在天然VND7启动子的控制下表达截短C末端的VND7蛋白，导致根中后生木质部导管、地上器官中的导管以及根中原生木质部导管的正常发育受到抑制。在大多数正在分化的导管中，VND7的表达模式与VND2至VND5的表达模式重叠。此外，酵母双杂交试验表明，VND7能够通过其包括NAC结构域在内的N末端与其他VND蛋白形成同二聚体和异二聚体。VND7在烟草BY-2细胞中的异源表达表明，VND7的稳定性可通过蛋白酶体介导的降解来调节。这些数据共同表明，VND7可能与VND2至VND5以及其他调节蛋白协同作用，调节根和茎中所有类型导管的分化。
