Identification of direct targets of transcription factor MYB46 provides insights into the transcriptional regulation of secondary wall biosynthesis
Identification of direct targets of transcription factor MYB46 provides insights into the transcriptional regulation of secondary wall biosynthesis
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DOI：
10.1007/s11103-014-0205-x
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发表时间：
2014-08-01
影响因子：
5.1
通讯作者：
Han, Kyung-Hwan
中科院分区：
文献类型：
--
作者：
Kim, Won-Chan;Kim, Joo-Yeol;Han, Kyung-Hwan
次生壁的形成需要参与次生壁组分生物合成的基因的协调转录调控。转录因子MYB46（At5g12870）是拟南芥次生壁形成的重要调控因子，它不仅激活生物合成基因，还激活参与次生壁形成的转录因子。最近，我们报道了MYB46直接调节次生壁相关纤维素合成酶（CESA 4，CESA 7和CESA 8）和甘露聚糖合成酶（CSLA 9）基因。然而，目前尚不清楚MYB46是否直接激活半纤维素和木质素的生物合成基因，这是次生壁的另外两种主要成分。基于观察到许多次生壁生物合成基因的启动子区含有MYB 46结合的顺式调控基序，我们假设MYB 46直接调控参与次生壁组分生物合成的基因。在这份报告中，我们描述了几条支持这一假设的实验证据。电泳迁移率变动分析和染色质免疫沉淀分析表明，MYB 46直接结合到参与木质素和木聚糖生物合成的13个基因的启动子。然后，我们使用类固醇受体为基础的诱导激活系统，以确认MYB46直接激活木聚糖和木质素生物合成基因的转录。此外，MYB46的异位上调导致木糖的显著增加和基于拟南芥中乙酰溴可溶性木质素测量的木质素含量的小幅增加。综上所述，我们得出结论，MYB46作为参与所有三种主要次生壁组分生物合成的基因的中心和直接调节因子发挥作用。
Secondary wall formation requires coordinated transcriptional regulation of the genes involved in the biosynthesis of the components of secondary wall. Transcription factor (TF) MYB46 (At5g12870) has been shown to function as a central regulator for secondary wall formation in Arabidopsis thaliana, activating biosynthetic genes as well as the TFs involved in the pathways. Recently, we reported that MYB46 directly regulates secondary wall-associated cellulose synthase (CESA4, CESA7, and CESA8) and a mannan synthase (CSLA9) genes. However, it is not known whether MYB46 directly activates the biosynthetic genes for hemicellulose and lignin, which are the other two major components of secondary wall. Based on the observations that the promoter regions of many of the secondary wall biosynthetic genes contain MYB46-binding cis-regulatory motif(s), we hypothesized that MYB46 directly regulates the genes involved in the biosynthesis of the secondary wall components. In this report, we describe several lines of experimental evidence in support of the hypothesis. Electrophoretic mobility shift assay and chromatin immunoprecipitation analysis showed that MYB46 directly binds to the promoters of 13 genes involved in lignin and xylan biosynthesis. We then used steroid receptor-based inducible activation system to confirm that MYB46 directly activates the transcription of the xylan and lignin biosynthetic genes. Furthermore, ectopic up-regulation of MYB46 resulted in a significant increase in xylose and a small increase in lignin content based on acetyl bromide soluble lignin measurements in Arabidopsis. Taken together, we conclude that MYB46 function as a central and direct regulator of the genes involved in the biosynthesis of all three major secondary wall components.