Kubo Hiroyoshi, Nozawa Shunsuke, Hiwatashi Takuma, Kondou Youichi, Nakabayashi Ryo, Mori Tetsuya, Saito Kazuki, Takanashi Kojiro, Kohchi Takayuki, Ishizaki Kimitsune
Department of Biology, Faculty of Science, Shinshu University, Matsumoto, 390-8621, Japan.
Graduate School of Science, Kobe University, Kobe, 657-8501, Japan.
J Plant Res. 2018 Sep;131(5):849-864. doi: 10.1007/s10265-018-1044-7. Epub 2018 May 29.
R2R3-MYB transcription factors constitute the largest gene family among plant transcription factor families. They became largely divergent during the evolution of land plants and regulate various biological processes. The functions of R2R3-MYBs are mostly characterized in seed plants but are poorly understood in non-seed plants. Here, we examined the function of two R2R3-MYB genes of Marchantia polymorpha (Mapoly0073s0038 and Mapoly0006s0226) that are closely related to subgroup 4 of the R2R3-MYB family. We performed LC/MS/MS metabolomics, RNA-seq analysis and expression analysis in overexpressors and knockout mutants of MpMYB14 and MpMYB02. Overexpression of MpMYB14 remarkably increased the amount of riccionidins, which are specific anthocyanins in liverworts and a few flowering plants. In contrast, overexpression of MpMYB02 increased the amount of several marchantins, which are characteristic cyclic bis (bibenzyl ether) compounds in M. polymorpha and related liverworts. Knockouts of MpMYB14 and MpMYB02 abolished the accumulation of riccionidins and marchantins, respectively. The expression of MpMYB14 was up-regulated by UV-B irradiation, N deficiency, and NaCl treatment, whereas the expression of MpMYB02 was down-regulated by NaCl treatment. Our results suggest that the regulatory framework of phenolic metabolism by R2R3-MYB was already established in early land plants.
R2R3-MYB转录因子是植物转录因子家族中最大的基因家族。在陆地植物的进化过程中，它们出现了很大的分化，并调控各种生物学过程。R2R3-MYB的功能在种子植物中研究得最为深入，但在非种子植物中却了解甚少。在此，我们研究了多形苔（Marchantia polymorpha）中两个与R2R3-MYB家族第4亚组密切相关的R2R3-MYB基因（Mapoly0073s0038和Mapoly0006s0226）的功能。我们对MpMYB14和MpMYB02的过表达植株和基因敲除突变体进行了液相色谱/串联质谱代谢组学、RNA测序分析和表达分析。MpMYB14的过表达显著增加了苔红素的含量，苔红素是地钱和少数开花植物中特有的花青素。相反，MpMYB02的过表达增加了几种多形苔素的含量，多形苔素是多形苔及相关地钱中特有的环状双（联苄醚）化合物。MpMYB14和MpMYB02的基因敲除分别消除了苔红素和多形苔素的积累。MpMYB14的表达受UV-B照射、氮缺乏和NaCl处理的上调，而MpMYB02的表达受NaCl处理的下调。我们的结果表明，R2R3-MYB对酚类代谢的调控框架在早期陆地植物中就已建立。
