背景+问题：Salt stress is a major constraint on plant growth and yield. Nitrogen (N) fertilizers are known to alleviate salt stress. However, the underlying molecular mechanisms remain unclear.  

主要发现：Here, we show that nitrate-dependent salt tolerance is mediated by OsMADS27 in rice. 

结果1-表达模式：The expression of OsMADS27 is specifically induced by nitrate. The salt-inducible expression of OsMADS27 is also nitrate dependent. 

结果2-敲除和过表达表型：OsMADS27 knockout mutants are more sensitive to salt stress than the wild type, whereas OsMADS27 overexpression lines are more tolerant. 

结果3-下游靶基因：Transcriptomic analyses revealed that OsMADS27 upregulates the expression of a number of known stress-responsive genes as well as those involved in ion homeostasis and antioxidation. We demonstrate that OsMADS27 directly binds to the promoters of OsHKT1.1 and OsSPL7 to regulate their expression. 

结果4-MADS27介导的盐耐受性依赖于硝酸盐：Notably, OsMADS27-mediated salt tolerance is nitrate dependent and positively correlated with nitrate concentration. 

结论：Our results reveal the role of nitrate-responsive OsMADS27 and its downstream target genes in salt tolerance, providing a molecular mechanism for the enhancement of salt tolerance by nitrogen fertilizers in rice. OsMADS27 overexpression increased grain yield under salt stress in the presence of sufficient nitrate, suggesting that OsMADS27 is a promising candidate for the improvement of salt tolerance in rice.

A working model for nitrate-responsive OsMADS27-promoted salt tolerance.

盐胁迫是植物生长和产量的一个主要限制因素。众所周知，氮肥可以缓解盐胁迫对植株的损伤。但是，潜在的分子机制仍不清楚。本文中，作者发现水稻中硝酸盐依赖性的盐耐受性是由OsMADS27介导的。OsMADS27基因的表达受到硝酸盐的特异性诱导。而且，OsMADS27基因的盐诱导表达也同样依赖于硝酸盐。相比于野生型，OsMADS27敲除突变体对于盐胁迫更加敏感；相反，OsMADS27过表达株系的盐耐受性更强。转录组分析显示，OsMADS27上调许多已知的胁迫响应基因以及参与离子稳态和抗氧化基因的表达。作者发现，OsMADS27能够直接结合到OsHKT1.1和OsSPL7启动子上，调控后者的表达。尤其是，OsMADS27介导的盐耐受性依赖于硝酸盐，并且与硝酸盐的浓度呈高度正相关。本文的研究结果揭示了响应于硝酸盐的基因OsMADS27的作用及其在盐耐受性中下游的靶基因，为水稻中施加氮肥以改善盐耐受性提供了分子层面的解释。OsMADS27过表达株系在足够氮肥的条件下，能够抵抗盐胁迫并增加籽粒产量，表明OsMADS27是未来用以改良水稻盐耐受性的一个重要候选基因。

**向成斌**