背景回顾：Nitrate is both an important nutrient and a critical signaling molecule that regulates plant metabolism, growth, and development. 

提出问题：Although several components of the nitrate signaling pathway have been identified, the molecular mechanism of nitrate signaling remains unclear. 

主要发现：Here, we showed that the growth-related transcription factors HOMOLOG OF BRASSINOSTEROID ENHANCED EXPRESSION2 INTERACTING WITH IBH1 (HBI1) and its three closest homologs (HBIs) positively regulate nitrate signaling in Arabidopsis thaliana. 

结果1-硝酸盐通过NLP6/7诱导HBI1：HBI1 is rapidly induced by nitrate through NLP6 and NLP7, which are master regulators of nitrate signaling. 

结果2-HBI突变导致植物对硝酸盐响应减弱：Mutations in HBIs result in the reduced effects of nitrate on plant growth and approximately 22% nitrate-responsive genes no longer to be regulated by nitrate. 

结果3-HBI与ROS：HBIs increase the expression levels of a set of antioxidant genes to reduce the accumulation of reactive oxygen species (ROS) in plants. 

结果4-HBI与CAT2/3突变干扰硝酸盐诱导的NLP7核定位：Nitrate treatment induces the nuclear localization of NLP7, whereas such promoting effects of nitrate are significantly impaired in the hbi-q and cat2 cat3 mutants, which accumulate high levels of H2O2. 

结论1-HBI-ROS-NLP7-Nitrate signalling：These results demonstrate that HBI-mediated ROS homeostasis regulates nitrate signal transduction through modulating the nucleocytoplasmic shuttling of NLP7.

结论2-负反馈调节环：Overall, our findings reveal that nitrate treatment reduces the accumulation of H2O2, and H2O2 inhibits nitrate signaling, thereby forming a feedback regulatory loop to regulate plant growth and development.

 摘 要 

硝酸盐是一种重要的营养物质，也是调节植物代谢、生长和发育的重要信号分子。虽然，目前已经鉴定了硝酸盐信号途径上的几个组分，但硝酸盐信号转导的分子机制仍然不清楚。本文中，作者发现生长相关的转录因子HBI1及其三个最近缘的同源物（HBIs）相互作用，正调控拟南芥中的硝酸盐信号转导。硝酸盐通过NLP6和NLP7快速诱导HBI1，而NLP6和NLP7是硝酸盐信号转导的主要调控因子。HBIs的突变会导致硝酸盐对植物生长的影响减弱，约22%的硝酸盐响应基因不再受硝酸盐的诱导。HBIs通过增加一些抗氧化基因的表达，减少植物体内活性氧物质（ROS）的积累。硝酸盐处理会诱导NLP7的核定位，而hbi-q和cat2 cat3突变体中硝酸盐的这种促进作用大大降低，并且这两种突变体植株体内均会积累较高水平的过氧化氢。这些结果表明，HBI介导的ROS稳态通过调节NLP7的核质穿梭，来调节硝酸盐的信号转导。综上，本文的研究结果表明，硝酸盐处理会减少了过氧化氢的积累，而过氧化氢则会抑制硝酸盐信号的传递，从而形成了一个反馈调节环来调节植物的生长和发育。