Mediator Complex Subunits MED2, MED5, MED16, and MED23 Genetically Interact in the Regulation of Phenylpropanoid Biosynthesis
Mediator Complex Subunits MED2, MED5, MED16, and MED23 Genetically Interact in the Regulation of Phenylpropanoid Biosynthesis
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DOI：
10.1105/tpc.17.00282
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发表时间：
2017-12-01
期刊：
影响因子：
11.6
通讯作者：
Chapple, Clint
中科院分区：
文献类型：
--
作者：
Dolan, Whitney L.;Dilkes, Brian P.;Chapple, Clint
苯丙烷途径是全球主要的碳汇，对植物适应性和生物能源原料工程具有重要意义。在拟南芥中，转录调节介质复合体的两个亚单位MED5a和MED5b的破坏导致苯丙醇积累增加。相比之下，半显性MED5b突变降低了表皮荧光4-3(ref4-3)，导致侏儒症和结构性抑制苯丙烷类物质的积累。在这里，我们报告了对ref4-3抑制子进行正向遗传筛查的结果。我们鉴定了13个在ref4-3背景下恢复生长和/或苯丙醇积累的独立株系。其中两个抑制子在不恢复可溶性苯丙烷积累的情况下恢复生长，表明ref4-3突变体的生长和代谢表型可以在基因上解缠。全基因组测序显示，除一个外，所有抑制子都携带MED5b或其他介体亚单位的突变。RNA-seq分析表明，ref4-3突变导致了基因表达的广泛变化，包括苯丙烷途径的负调控因子上调，并且抑制物逆转了许多这些变化。总之，我们的数据强调了单个介体亚单位的相互依赖，并为介体复合体对苯丙烷类生物合成的转录调控提供了更好的洞察力。
The phenylpropanoid pathway is a major global carbon sink and is important for plant fitness and the engineering of bioenergy feedstocks. In Arabidopsis thaliana, disruption of two subunits of the transcriptional regulatory Mediator complex, MED5a and MED5b, results in an increase in phenylpropanoid accumulation. By contrast, the semidominant MED5b mutation reduced epidermal fluorescence4-3 (ref4-3) results in dwarfism and constitutively repressed phenylpropanoid accumulation. Here, we report the results of a forward genetic screen for suppressors of ref4-3. We identified 13 independent lines that restore growth and/or phenylpropanoid accumulation in the ref4-3 background. Two of the suppressors restore growth without restoring soluble phenylpropanoid accumulation, indicating that the growth and metabolic phenotypes of the ref4-3 mutant can be genetically disentangled. Whole-genome sequencing revealed that all but one of the suppressors carry mutations in MED5b or other Mediator subunits. RNA-seq analysis showed that the ref4-3 mutation causes widespread changes in gene expression, including the upregulation of negative regulators of the phenylpropanoid pathway, and that the suppressors reverse many of these changes. Together, our data highlight the interdependence of individual Mediator subunits and provide greater insight into the transcriptional regulation of phenylpropanoid biosynthesis by the Mediator complex.