Du Qingguo, Lv Wenshuai, Guo Yu, Yang Juan, Wang Shanhong, Li Wen-Xue
National Engineering Laboratory for Crop Molecular Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
Plant Physiol. 2022 Jun 1;189(2):1095-1109. doi: 10.1093/plphys/kiac114.
Recent findings have revealed the important roles of microRNAs (miRNAs) in the secondary responses to oxidative damage caused by iron (Fe) excess. However, the functional importance of miRNAs in plant responses to Fe deficiency remains to be explored. Here, we show that the expression level of miR164 in Arabidopsis (Arabidopsis thaliana) roots was repressed by Fe deficiency. Primary root length, lateral root number, ferric reductase activity, and mRNA abundance of IRON-REGULATED TRANSPORTER1 (IRT1) and FERRIC REDUCTION OXIDASE2 (FRO2) were higher in the mir164b mutant than in the wild-type (WT) under Fe-deficient conditions. Analysis of the Fe concentrations and ferric reductase activities in the roots of miR164 knockdown transgenic plants showed that members of the miR164 family had different functions in Fe-deficiency responses. Promoter::GUS analysis showed that NAM/ATAF/CUC (NAC) domain transcription factor5 (NAC5) is regulated at both transcriptional and posttranscriptional levels under Fe-deficient conditions. Transgenic Arabidopsis plants overexpressing NAC5 were more tolerant of Fe deficiency than the WT. NAC5 has transactivation activity and directly transactivates the expression of Nuclear Factor Y, Subunit A8 (NFYA8), as demonstrated by chromatin immunoprecipitation followed by quantitative polymerase chain reaction, electrophoretic mobility shift assay (EMSA), and dual-luciferase reporter assay. Like overexpression of NAC5, overexpression of NFYA8 increases primary root length, lateral root number, ferric reductase activity, and mRNA abundance of IRT1 and FRO2 under Fe-deficient conditions. Thus, MIR164b is important for Fe-deficiency responses by its regulation of the NAC5-NFYA8 module.
最近的研究结果揭示了微小RNA（miRNA）在铁（Fe）过量引起的氧化损伤二次应答中的重要作用。然而，miRNA在植物对缺铁应答中的功能重要性仍有待探索。在此，我们表明缺铁会抑制拟南芥（Arabidopsis thaliana）根中miR164的表达水平。在缺铁条件下，mir164b突变体的主根长度、侧根数量、铁还原酶活性以及铁调节转运蛋白1（IRT1）和铁还原氧化酶2（FRO2）的mRNA丰度均高于野生型（WT）。对miR164敲低转基因植物根中铁浓度和铁还原酶活性的分析表明，miR164家族成员在缺铁应答中具有不同功能。启动子::GUS分析表明，NAM/ATAF/CUC（NAC）结构域转录因子5（NAC5）在缺铁条件下在转录和转录后水平均受到调控。过表达NAC5的转基因拟南芥植物比WT更耐缺铁。如染色质免疫沉淀后进行定量聚合酶链反应、电泳迁移率变动分析（EMSA）和双荧光素酶报告基因分析所示，NAC5具有反式激活活性，并直接反式激活核因子Y亚基A8（NFYA8）的表达。与过表达NAC5一样，过表达NFYA8在缺铁条件下会增加主根长度、侧根数量、铁还原酶活性以及IRT1和FRO2的mRNA丰度。因此，MIR164b通过调控NAC5-NFYA8模块对缺铁应答很重要。
