背景回顾：In plants, nitrate is the dominant nitrogen (N) source and a critical nutrient signal regulating various physiological and developmental processes. Nitrate-responsive gene regulatory networks are widely believed to control growth, development, and life cycle in addition to N acquisition and utilization, and NIN-LIKE PROTEIN (NLP) transcriptional activators have been identified as the master regulators governing the networks. 

提出问题：However, it remains to be elucidated how nitrate signaling regulates respective physiological and developmental processes. 

主要发现：Here, we have identified a new nitrate-activated transcriptional cascade involved in chloroplast development and the maintenance of chloroplast function in Arabidopsis. 

结果1-转录级联：This cascade consisting of NLP7 and two homeodomain-leucine zipper (HD-Zip) class I transcription factors, HOMEOBOX PROTEIN52 (HB52) and HB54, was responsible for nitrate- and light-dependent expression of VAR2 encoding the FtsH2 subunit of the chloroplast FtsH protease involved in the quality control of photodamaged thylakoid membrane proteins. 

结果2-生物学功能：Consistently, the nitrate-activated NLP7-HB52/54-VAR2 pathway underpinned photosynthetic light energy utilization, especially in high light environments. Furthermore, genetically enhancing the NLP7-HB52/54-VAR2 pathway resulted in improved light energy utilization under high light and low N conditions, a superior agronomic trait. 

结论：These findings shed light on a new role of nitrate signaling and a novel mechanism for integrating information on N nutrient and light environments, providing a hint for enhancing the light energy utilization of plants in low N environments.

NLP7-HB52/54-VAR2作用于高光和低氮条件下的叶绿体发育和光能利用。

** Shuichi Yanagisawa **