Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.
Molecular and Biological Agricultural Sciences Program, Taiwan International Graduate Program, Academia Sinica and National Chung Hsing University, Taipei, 11529, Taiwan.
New Phytol. 2024 Jan;241(1):504-515. doi: 10.1111/nph.19293. Epub 2023 Sep 27.
Plants can record external stimuli in mobile mRNAs and systemically deliver them to distal tissues to adjust development. Despite the identification of thousands of mobile mRNAs, the functional relevance of mobile mRNAs remains limited. Many mobile mRNAs are synthesized in the source cells that perceive environmental stimuli, but specifically exert their functions upon transportation to the recipient cells. However, the translation of mobile mRNA-encoded protein in the source cells could locally activate downstream target genes. How plants avoid ectopic functions of mobile mRNAs in the source cells to achieve tissue specificity remains to be elucidated. Here, we show that Arabidopsis AGAMOUS-LIKE 24 (AGL24) is a mobile mRNA whose movement is necessary and sufficient to specify floral organ identity. Although AGL24 mRNA is expressed in vegetative tissues, AGL24 protein exclusively accumulates in the shoot apex. In leaves, AGL24 proteins are degraded to avoid ectopically activating its downstream target genes. Our results reveal how selective protein degradation in source cells provides a strategy to limit the local effects associated with proteins encoded by mobile mRNAs, which ensures that mobile mRNAs specifically trigger systemic responses only in recipient tissues.
植物可以在移动的 mRNA 中记录外部刺激，并将其系统地传递到远端组织以调节发育。尽管已经鉴定出数千种移动的 mRNA，但移动 mRNA 的功能相关性仍然有限。许多移动的 mRNA 是在感知环境刺激的源细胞中合成的，但只有在运输到受体细胞后才会发挥其功能。然而，移动 mRNA 编码的蛋白质在源细胞中的翻译可以局部激活下游靶基因。植物如何避免移动 mRNA 在源细胞中的异位功能以实现组织特异性仍有待阐明。在这里，我们表明拟南芥 AGAMOUS-LIKE 24（AGL24）是一种移动的 mRNA，其运动对于指定花器官的身份是必要和充分的。尽管 AGL24 mRNA 在营养组织中表达，但 AGL24 蛋白仅在茎尖中积累。在叶子中，AGL24 蛋白被降解以避免异位激活其下游靶基因。我们的结果揭示了源细胞中选择性蛋白降解如何提供一种策略来限制与移动 mRNA 编码的蛋白质相关的局部效应，这确保了移动 mRNA 仅在受体组织中特异性触发系统反应。
