As one of the largest families of transcription factors in plants, the R2R3-MYB proteins play important roles in diverse biological processes including growth and development, primary and secondary metabolism such as flavonoid and anthocyanin biosynthesis as well as abiotic and biotic stress responses. However, functions of R2R3-MYB genes in rapeseed (Brassica napus L.) remain elusive. Here, we characterized BnaMYB111L, which is homologous to Arabidopsis MYB111 and encodes an R2R3-MYB protein in rapeseed. BnaMYB111L is responsive to abscisic acid (ABA), heat, cold, hydrogen peroxide and fungal pathogen Sclerotinia scelerotiorum treatments through quantitative RT-PCR assay. BnaMYB111L encodes a transcriptional activator and is localized exclusively to nuclei. Interestingly, overexpression of BnaMYB111L in tobacco (Nicotiana benthamiana) and rapeseed protoplasts promoted reactive oxygen species (ROS) production and hypersensitive response-like cell death, accumulation of malondialdehyde (MDA) as well as degradation of chlorophyll. Furthermore, BnaMYB111L expression evoked the alterations of transcript levels of genes encoding ROS-producing enzyme, vacuolar processing enzymes and genes implicated in defense responses. A further dual luciferase reporter assay indicated that BnaMYB111L activated the expression of RbohB, MC4 and ACRE132, which are involved in ROS generation, cell death as well as defense responses. Taken together, this study characterized the function of rapeseed MYB111L and identified its putative target genes involved in ROS production and cell death.

中文翻译：

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来自油菜籽的R2R3-MYB转录因子BnaMYB111L调节活性氧的积累和超敏性细胞死亡。

作为植物中最大的转录因子家族之一，R2R3-MYB蛋白在包括生长发育，类黄酮和花青素生物合成等主要和次要代谢以及非生物和生物胁迫响应在内的多种生物过程中发挥重要作用。但是，R2R3-MYB基因在油菜（甘蓝型油菜）中的功能仍然难以捉摸。在这里，我们表征了BnaMYB111L，它与拟南芥MYB111同源，并在油菜籽中编码R2R3-MYB蛋白。BnaMYB111L通过定量RT-PCR分析对脱落酸（ABA），高温，低温，过氧化氢和真菌病原菌核盘菌（Sclerotonia scelerotiorum）处理有反应。BnaMYB111L编码转录激活因子，并且仅定位于细胞核。有趣的是，BnaMYB111L在烟草（Nicotiana benthamiana）和油菜原生质体中的过表达促进了活性氧（ROS）的产生和超敏反应样细胞的死亡，丙二醛（MDA）的积累以及叶绿素的降解。此外，BnaMYB111L表达引起编码产生ROS的酶，液泡加工酶和涉及防御反应的基因的转录水平的改变。进一步的双重荧光素酶报告基因测定表明，BnaMYB111L激活了RbohB，MC4和ACRE132的表达，这些表达与ROS的产生，细胞死亡以及防御反应有关。两者合计，这项研究表征了油菜MYB111L的功能，并确定了其与ROS产生和细胞死亡有关的推定靶基因。