MicroRNAs are small noncoding RNAs that regulate gene expression by targeting complementary mRNA molecules. Among them, microRNA408 (miR408) is an ancient microRNA influencing plant growth and aiding in abiotic stress adaptation. We proved that miR408 sliced () directly by degradome sequencing. However, the mechanisms underlying the balance between growth and stress response of rice ( L.) controlled by miR408 remain unclear. We conducted a study comparing Nipponbare (wild-type, WT) plants with miR408–3poverexpression (miR408–3p-OX) and -overexpression (UCL7OX) plants under normal and heat stress conditions. Through RNA-sequencing, physiological measurements, and phenotype examination, we observed that miR408 overexpression resulted in increased dry weight and grain yield, higher levels of ATP and non-structural carbohydrates (NSC), improved photosynthesis, and reduced HO content, antioxidant enzyme activity, and ATPase activity in seedling plants compared to UCL7-OX plants. Additionally, the application of HO scavengers, such as ascorbic acid (ASA) and dimethylthiourea (DMTU), further enhanced dry weight and photosynthesis by reducing HO levels. Under heat stress conditions, miR408 overexpression sharply increased HO content, antioxidant enzyme activity, ATP levels, and ATPase activity compared to UCL7-OX plants, thereby enhancing heat tolerance in rice seedlings. These findings suggest that miR408 and its target gene participate in regulating energy homeostasis to achieve a balance between growth and heat response. This regulation involves modulating HO levels and optimizing the relationship between the target of rapamycin (TOR) and SNF1-related protein kinase 1 (SnRK1) in rice.

中文翻译：

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MiR408 平衡水稻的植物生长和热响应

MicroRNA 是小型非编码 RNA，通过靶向互补 mRNA 分子来调节基因表达。其中，microRNA408（miR408）是一种古老的microRNA，影响植物生长并帮助适应非生物胁迫。我们通过降解组测序证明了miR408直接切片()。然而，miR408控制的水稻生长和胁迫反应之间的平衡机制仍不清楚。我们进行了一项研究，比较正常和热胁迫条件下具有 miR408–3p 过表达 (miR408–3p-OX) 和 miR408–3p 过表达 (UCL7OX) 植物的日本晴（野生型，WT）植物。通过RNA测序、生理测量和表型检查，我们观察到miR408过表达导致干重和谷物产量增加、ATP和非结构碳水化合物（NSC）水平升高、光合作用改善、H2O含量、抗氧化酶活性降低，以及与 UCL7-OX 植物相比幼苗植物中的 ATP 酶活性。此外，抗坏血酸（ASA）和二甲基硫脲（DMTU）等H2O清除剂的应用通过降低H2O水平进一步增强了干重和光合作用。在热胁迫条件下，与UCL7-OX植物相比，miR408过表达显着增加了H2O含量、抗氧化酶活性、ATP水平和ATP酶活性，从而增强了水稻幼苗的耐热性。这些发现表明miR408及其靶基因参与调节能量稳态以实现生长和热反应之间的平衡。这种调节涉及调节 HO 水平并优化水稻中雷帕霉素 (TOR) 靶点和 SNF1 相关蛋白激酶 1 (SnRK1) 之间的关系。