MYB46-Mediated Transcriptional Regulation of Secondary Wall Biosynthesis
MYB46-Mediated Transcriptional Regulation of Secondary Wall Biosynthesis
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DOI：
10.1093/mp/sss076
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发表时间：
2012-09-01
期刊：
影响因子：
27.5
通讯作者：
Han, Kyung-Hwan
中科院分区：
文献类型：
--
作者：
Ko, Jae-Heung;Kim, Won-Chan;Han, Kyung-Hwan
次生壁的形成需要参与主要次生壁组分（例如纤维素、半纤维素和木质素）的生物合成的基因的协调转录调控。尽管植物生物学的许多方面已经利用各种模式物种得到了广泛的阐明，但我们目前对次生壁形成的理解是有限的。复杂的转录网络似乎参与次生壁生物合成的协调调节（Ko等，2009; Demura和Ye，2010; Zhu等人，2010; Lee等人，2011;最近的综述，参见Wang和狄克逊，2012）。最近，MYB 46（at 5g 12870）已被证明是次生壁形成的中心调节因子（图1）（Zhong等人，2007; Ko等人，2009年）。MYB 46主要在花序茎中表达，特别是在经历次生壁增厚的纤维和木质部细胞中，但不在薄壁细胞中表达。MYB 46或其接近的同源物MYB 83（at 3g 08500）的过表达上调参与次生壁生物合成的基因（例如纤维素、半纤维素和木质素生物合成基因），并导致次生壁的异位沉积，即使在正常薄壁细胞中也是如此（Ko et al.，2009年）。另一方面，MYB 46的显性抑制显著减少转基因植物的纤维和导管中的次生壁增厚（Zhong et al.，2007年）。综合起来，这些观察结果表明MYB 46和MYB 83作为次生细胞壁形成的主转录开关起作用。此外，来自其他植物物种的几种MYB 46直向同源物也显示出作为次生壁形成的主开关，包括来自松树的PtMYB 4、来自桉树的egMYB 2、来自白杨的PtrMYB 3/PtrMYB 20、来自水稻的OsMYB 46和来自玉米的ZmMYB 46（Zhong et al. 2011; Wang和狄克逊，2012）。Ko等等人（2009）通过在地塞米松诱导型启动子的控制下表达MYB 46，在拟南芥植物中用诱导型次生壁增厚系统进行了时程转录组分析。该研究鉴定了总共42种转录因子，其表达与次生壁生物合成基因的诱导一致或先于次生壁生物合成基因的诱导。基于基因的时程表达模式，在次生壁生物合成的转录调控方面，开发了一个试探性的转录因子的层次关系。几个Nac结构域转录因子已被鉴定为次生壁形成的关键转录激活因子，它们位于转录网络中MYB 46的上游。血管相关NAC结构域6
Formation of secondary wall requires coordinated transcriptional regulation of the genes involved in the biosynthesis of major secondary wall components (eg cellulose, hemicellulose, and lignin). even though many aspects of plant biology have been extensively elucidated using various model species, our current understanding of secondary wall formation is limited. complex transcriptional networks appear to be involved in the coordinated regulation of secondary wall biosynthesis (Ko et al., 2009; Demura and Ye, 2010; Zhu et al., 2010; lee et al., 2011; for a recent review, see Wang and Dixon, 2012). Recently, MYB46 (at5g12870) has been shown to function as a central regulator for secondary wall formation (Figure 1)(Zhong et al., 2007; Ko et al., 2009). MYB46 is predominantly expressed in inflorescence stems, specifically in both fibers and xylem cells undergoing secondary wall thickening but not in parenchymatous cells. Overexpression of MYB46 or its close homolog MYB83 (at3g08500) up-regulates the genes involved in secondary wall biosynthesis (eg cellulose, hemicellulose, and lignin biosynthesis genes) and causes ectopic deposition of secondary walls even in the cells that are normally parenchymatous (Ko et al., 2009). On the other hand, dominant suppression of MYB46 significantly reduces secondary wall thickening in the fibers and vessels of the transgenic plants (Zhong et al., 2007). taken together, these observations suggest that MYB46 and MYB83 function as a master transcriptional switch for secondary cell wall formation. Furthermore, several MYB46 orthologs from other plant species have also been shown to function as a master switch for secondary wall formation, including PtMYB4 from pine, egMYB2 from eucalyptus, PtrMYB3/PtrMYB20 from poplar, OsMYB46 from rice, and ZmMYB46 from maize (Zhong et al., 2011; Wang and Dixon, 2012). Ko et al.(2009) performed a time-course transcriptome profiling with an inducible secondary wall thickening system in Arabidopsis plants by expressing MYB46 under the control of dexamethasone-inducible promoter. this study identified a total of 42 transcription factors whose expressions coincide with or precede the induction of secondary wall biosynthetic genes. Based on the time-course expression pattern of the genes, a tentative hierarchical relationship of the transcription factors was developed in regard to transcriptional regulation of secondary wall biosynthesis. Several Nac domain transcription factors have been identified as key transcriptional activators of secondary wall formation, which are located at the upstream of MYB46 in the transcriptional network. VASCULAR-RELATED NAC-DOMAIN6