BACKGROUND MicroRNAs (miRNAs) play crucial roles in the regulation of plant development and growth, but little information is available concerning their roles during grain development under different nitrogen (N) application levels. Our objective was to identify miRNAs related to the regulation of grain characteristics and the response to different N fertilizer conditions. RESULTS A total of 79 miRNAs (46 known and 33 novel miRNAs) were identified that showed significant differential expression during grain development under both high nitrogen (HN) and low nitrogen (LN) treatments. The miRNAs that were significantly upregulated early in grain development target genes involved mainly in cell differentiation, auxin-activated signaling, and transcription, which may be associated with grain size; miRNAs abundant in the middle and later stages target genes mainly involved in carbohydrate and nitrogen metabolism, transport, and kinase activity and may be associated with grain filling. Additionally, we identified 50 miRNAs (22 known and 28 novel miRNAs), of which 11, 9, and 39 were differentially expressed between the HN and LN libraries at 7, 17, and 27 days after anthesis (DAA). The miRNAs that were differentially expressed in response to nitrogen conditions target genes involved mainly in carbohydrate and nitrogen metabolism, the defense response, and transport as well as genes that encode ubiquitin ligase. Only one novel miRNA (PC-5p-2614_215) was significantly upregulated in response to LN treatment at all three stages, and 21 miRNAs showed significant differential expression between HN and LN conditions only at 27 DAA. We therefore propose a model for target gene regulation by miRNAs during grain development with N-responsive patterns. CONCLUSIONS The potential targets of the identified miRNAs are related to various biological processes, such as carbohydrate/nitrogen metabolism, transcription, cellular differentiation, transport, and defense. Our results indicate that miRNA-mediated networks, via posttranscriptional regulation, play crucial roles in grain development and the N response, which determine wheat grain weight and quality. Our study provides useful information for future research of regulatory mechanisms that focus on improving grain yield and quality.

中文翻译：

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鉴定发育中的小麦籽粒中可能参与调控籽粒特性和对氮水平响应的微小RNA。

背景技术微小RNA（miRNA）在调节植物发育和生长中起关键作用，但是关于在不同氮（N）施用水平下在谷物发育期间它们的作用的信息很少。我们的目标是鉴定与调控谷物特性和对不同氮肥条件的响应有关的miRNA。结果鉴定出总共79种miRNA（46种已知的miRNA和33种新颖的miRNA），在高氮（HN）和低氮（LN）处理下，在谷物发育过程中均表现出明显的差异表达。在谷物发育早期被显着上调的miRNA靶向基因主要涉及细胞分化，生长素激活的信号传导和转录，这可能与晶粒大小有关。在中后期阶段丰富的miRNA靶向主要涉及碳水化合物和氮代谢，转运和激酶活性的基因，并且可能与谷物充实有关。此外，我们鉴定了50个miRNA（22个已知的miRNA和28个新颖的miRNA），其中11、9和39个在花期（DAA）之后的7、17和27天在HN和LN库之间差异表达。响应氮条件而差异表达的miRNA靶向的基因主要涉及碳水化合物和氮的代谢，防御反应和转运，以及编码泛素连接酶的基因。在所有三个阶段中，只有一种新的miRNA（PC-5p-2614_215）响应LN处理而显着上调，而21种miRNA仅在27 DAA时才显示HN和LN条件之间的显着差异表达。因此，我们提出了具有N响应模式的谷物发育过程中miRNA调控靶基因的模型。结论鉴定出的miRNA的潜在靶标与各种生物过程有关，例如糖/氮代谢，转录，细胞分化，转运和防御。我们的结果表明，通过转录后调控，miRNA介导的网络在谷物发育和氮素响应中起着至关重要的作用，这决定了小麦籽粒的重量和品质。我们的研究为未来研究侧重于提高谷物产量和质量的调节机制提供了有用的信息。结论鉴定出的miRNA的潜在靶标与各种生物过程有关，例如糖/氮代谢，转录，细胞分化，转运和防御。我们的结果表明，通过转录后调控，miRNA介导的网络在谷物发育和氮素响应中起着至关重要的作用，这决定了小麦籽粒的重量和品质。我们的研究为未来研究侧重于提高谷物产量和质量的调节机制提供了有用的信息。结论鉴定出的miRNA的潜在靶标与各种生物过程有关，例如碳水化合物/氮素代谢，转录，细胞分化，转运和防御。我们的结果表明，通过转录后调控，miRNA介导的网络在谷物发育和氮素响应中起着至关重要的作用，这决定了小麦籽粒的重量和品质。我们的研究为未来研究侧重于提高谷物产量和质量的调节机制提供了有用的信息。