Figure 1 Ectopic expression of GmNAC115m5 increased the stress resilience of soybean composite plants to salt and drought stress, whereas ectopic expression of gmamiR164a decreased the stress resilience of plants to salt and drought stress.
研究人员首先发现,gma-miR164a在大豆根中高表达,但在PEG(模拟干旱)、NaCl和ABA处理下其表达显著下调,表明其参与胁迫响应。进一步研究表明,gma-miR164a负调控大豆抗旱耐盐能力:过表达该miRNA的转基因拟南芥种子在盐和甘露醇胁迫下萌发率更低,根系生长受抑制更明显,且对ABA不敏感,表现出更高的胁迫敏感性。
Figure 2 DNA affinity purification sequencing identified genome-wide downstream target genes of GmNAC115.
相反,其靶基因GmNAC115编码一个NAC转录因子,被证实为正向调控因子。GmNAC115在胁迫下表达上调,过表达该基因显著增强拟南芥和大豆毛状根的耐旱耐盐能力。DNA亲和纯化测序(DAP-seq)结合酵母单杂、EMSA和双荧光素酶实验,鉴定出GmNAC115直接结合并激活下游基因GmWRKY21、GmAPX6(抗坏血酸过氧化物酶)和GmPOD25(过氧化物酶)的启动子。
Figure 3 The GmWRKY21 transcription factor positively regulates the expression of GmAPX6 and GmPOD25 by binding W-box cis-acting elements.
更重要的是,GmWRKY21也能结合GmAPX6和GmPOD25启动子中的W-box元件,进一步放大抗氧化防御信号。功能验证显示,过表达这三个基因均能减少ROS积累、提高抗氧化酶活性,并显著增强大豆毛状根的抗逆性。
Schematic diagram of the possible mechanisms underlying the response of the gma-miR164a/GmNAC115 module to drought and salt stress