National Key Laboratory for Crop Genetic Improvement and National Center of Plant Gene Research, Huazhong Agricultural University, Wuhan 430070, China.
Plant Physiol. 2012 Mar;158(3):1382-94. doi: 10.1104/pp.111.190488. Epub 2012 Jan 23.
The highly conserved plant microRNA, miR156, is an essential regulator for plant development. In Arabidopsis (Arabidopsis thaliana), miR156 modulates phase changing through its temporal expression in the shoot. In contrast to the gradual decrease over time in the shoot (or whole plant), we found that the miR156 level in rice (Oryza sativa) gradually increased from young leaf to old leaf after the juvenile stage. However, the miR156-targeted rice SQUAMOSA-promoter binding-like (SPL) transcription factors were either dominantly expressed in young leaves or not changed over the time of leaf growth. A comparison of the transcriptomes of early-emerged old leaves and later-emerged young leaves from wild-type and miR156 overexpression (miR156-OE) rice lines found that expression levels of 3,008 genes were affected in miR156-OE leaves. Analysis of temporal expression changes of these genes suggested that miR156 regulates gene expression in a leaf age-dependent manner, and miR156-OE attenuated the temporal changes of 2,660 genes. Interestingly, seven conserved plant microRNAs also showed temporal changes from young to old leaves, and miR156-OE also attenuated the temporal changes of six microRNAs. Consistent with global gene expression changes, miR156-OE plants resulted in dramatic changes including precocious leaf maturation and rapid leaf/tiller initiation. Our results indicate that another gradient of miR156 is present over time, a gradual increase during leaf growth, in addition to the gradual decrease during shoot growth. Gradually increased miR156 expression in the leaf might be essential for regulating the temporal expression of genes involved in leaf development.
高度保守的植物 microRNA，miR156，是植物发育的重要调节因子。在拟南芥（Arabidopsis thaliana）中，miR156 通过在芽中的时间表达来调节相转变。与芽（或整株植物）中随时间逐渐减少形成对比的是，我们发现，在幼年期之后，水稻（Oryza sativa）中 miR156 的水平从幼叶逐渐增加到老叶。然而，miR156 靶向的水稻 SQUAMOSA-PROMOTER BINDING-LIKE（SPL）转录因子要么在幼叶中强烈表达，要么在叶片生长过程中没有变化。对野生型和 miR156 过表达（miR156-OE）水稻系中早期出现的老叶和后期出现的幼叶的转录组进行比较，发现 miR156-OE 叶片中有 3008 个基因的表达水平受到影响。对这些基因的时间表达变化进行分析表明，miR156 以叶片年龄依赖的方式调节基因表达，miR156-OE 减弱了 2660 个基因的时间变化。有趣的是，七个保守的植物 microRNA 也表现出从幼叶到老叶的时间变化，miR156-OE 也减弱了六个 microRNA 的时间变化。与全局基因表达变化一致，miR156-OE 植物导致了包括叶片成熟提前和叶片/分蘖快速起始在内的显著变化。我们的结果表明，除了在芽生长过程中逐渐减少外，在叶片生长过程中，miR156 随着时间的推移存在另一个梯度，逐渐增加。叶片中 miR156 表达的逐渐增加可能是调节叶片发育相关基因时间表达的关键。
