Ding Qing Qian, Wang Xiao Ting, Hu Li Qin, Qi Xin, Ge Lin Hao, Xu Wei Ya, Xu Zhao Shi, Zhou Yong Bin, Jia Guan Qing, Diao Xian Min, Min Dong Hong, Ma You Zhi, Chen Ming
National Key Facility For Crop Gene Resource and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crop, Ministry of Agriculture, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
State Key Laboratory of Arid Region Crop Adversity Biology, College of Agronomy, Northwest A&F University, Yangling 712100, China.
Yi Chuan. 2018 Apr 20;40(4):327-338. doi: 10.16288/j.yczz.17-315.
Myeloblastosis (MYB) transcription factors are one of the largest families of transcription factors in higher plants. They play an important role in plant development, defense response processes, and non-biological stresses, i.e., drought stress. Foxtail millet (Setaria italica L.), originated in China, is resistant to drought and low nutrition stresses and has been regarded as an ideal material for studying abiotic stress resistance in monocotyledon. In this study, we ran a transcription profile analysis of zheng 204 under low-nitrogen conditions and identified a MYB-like transcription factor SiMYB42, which was up-regulated under low-nitrogen stress. Phylogenetic tree analysis showed that SiMYB42 belongs to R2R3-MYB subfamily and has two MYB conserved domains. Expression pattern analysis showed that SiMYB42 was significantly up-regulated under various stress conditions, including low-nitrogen stress, high salt, drought and ABA conditions. The results of subcellular localization, quantitative real-time PCR and transcriptional activation analysis indicated that SiMYB42 protein localizes to the nucleus and cell membrane of plant cells, mainly expressed in the leaf or root of foxtail millet, and has transcription activation activity. Functional analysis showed that there was no significant difference between transgenic SiMYB42 Arabidopsis and wild-type (WT) Arabidopsis under normal conditions; however, under low-nitrogen condition, the root length, surface area and seedling fresh weight in transgenic SiMYB42 Arabidopsis, were significantly higher than their counterparts in WT. These results suggest that SiMYB42 transgenic plants exhibit higher tolerance to low-nitrogen stress. Expression levels of nitrate transporters genes NRT2.1, NRT2.4 and NRT2.5, which are the transcriptional targets of SiMYB42, were higher in transgenic SiMYB42 Arabidopsis plants than those in WT; the promoter regions of NRT2.1, NRT2.4 and NRT2.5 all have MYB binding sites. These results indicate that SiMYB42 might enhance foxtail millet tolerance to low-nitrogen condition through regulating the expression of nitrate transporter genes. This study reveals the possible functions of SiMYB42 in a low-nitrogen stress response pathway, and provides a foundation for further understanding the entire regulation network of foxtail millet in response to low-nitrogen stress.
成髓细胞瘤（MYB）转录因子是高等植物中最大的转录因子家族之一。它们在植物发育、防御反应过程以及非生物胁迫（即干旱胁迫）中发挥着重要作用。谷子（Setaria italica L.）原产于中国，对干旱和低营养胁迫具有抗性，被视为研究单子叶植物抗非生物胁迫的理想材料。在本研究中，我们对低氮条件下的郑204进行了转录谱分析，并鉴定出一个类MYB转录因子SiMYB42，其在低氮胁迫下上调表达。系统发育树分析表明，SiMYB42属于R2R3-MYB亚家族，具有两个MYB保守结构域。表达模式分析表明，SiMYB42在包括低氮胁迫、高盐、干旱和脱落酸条件在内的各种胁迫条件下均显著上调表达。亚细胞定位、定量实时PCR和转录激活分析结果表明，SiMYB42蛋白定位于植物细胞的细胞核和细胞膜，主要在谷子的叶或根中表达，并具有转录激活活性。功能分析表明，在正常条件下，转基因SiMYB42拟南芥与野生型（WT）拟南芥之间没有显著差异；然而，在低氮条件下，转基因SiMYB42拟南芥的根长、表面积和幼苗鲜重均显著高于野生型。这些结果表明，SiMYB42转基因植物对低氮胁迫表现出更高的耐受性。作为SiMYB42转录靶标的硝酸盐转运蛋白基因NRT2.1、NRT2.4和NRT2.5在转基因SiMYB42拟南芥植物中的表达水平高于野生型；NRT2.1、NRT2.4和NRT2.5的启动子区域均具有MYB结合位点。这些结果表明，SiMYB42可能通过调节硝酸盐转运蛋白基因的表达来增强谷子对低氮条件的耐受性。本研究揭示了SiMYB42在低氮胁迫响应途径中的可能功能，并为进一步了解谷子响应低氮胁迫的整个调控网络提供了基础。
