Biocenter Klein Flottbek, Molekulare Pflanzengenetik, University Hamburg, Ohnhorststr. 18, Hamburg 22609, Germany.
Department II, Max Planck Institute of Molecular Plant Physiology, Am Mühlenberg 1, Potsdam-Golm 14476, Germany.
New Phytol. 2018 Apr;218(1):29-40. doi: 10.1111/nph.15025. Epub 2018 Feb 8.
Contents Summary 29 I. Introduction 29 II. Phloem as a conduit for macromolecules 30 III. Classes of phloem transported RNAs and their function 32 IV. Mode of RNA transport 35 V. Conclusions 37 Acknowledgements 37 References 37 SUMMARY: In higher plants, small noncoding RNAs and large messenger RNA (mRNA) molecules are transported between cells and over long distances via the phloem. These large macromolecules are thought to get access to the sugar-conducting phloem vessels via specialized plasmodesmata (PD). Analyses of the phloem exudate suggest that all classes of RNA molecules, including silencing-induced RNAs (siRNAs), micro RNAs (miRNAs), transfer RNAs (tRNAs), ribosomal RNA (rRNAs) and mRNAs, are transported via the vasculature to distant tissues. Although the functions of mobile siRNAs and miRNAs as signalling molecules are well established, we lack a profound understanding of mobile mRNA function(s) in recipient cells and tissues, and how they are selected for transport. A surprisingly high number of up to thousands of mRNAs were described in diverse plant species such as cucumber, pumpkin, Arabidopsis and grapevine to move long distances over graft junctions to distinct body parts. In this review, we present an overview of the classes of mobile RNAs, the potential mechanisms facilitating RNA long-distance transport, and the roles of mobile RNAs in regulating transcription and translation. Furthermore, we address potential function(s) of mobile protein-encoding mRNAs with respect to their characteristics and evolutionary constraints.
内容摘要 29 I. 引言 29 II. 韧皮部作为大分子的运输导管 30 III. 韧皮部运输的 RNA 种类及其功能 32 IV. RNA 运输方式 35 V. 结论 37 致谢 37 参考文献 37 摘要：在高等植物中，小非编码 RNA 和大信使 RNA（mRNA）分子通过韧皮部在细胞间和长距离进行运输。这些大分子被认为通过特化的胞间连丝（PD）进入含糖的韧皮部导管。对韧皮部渗出物的分析表明，包括沉默诱导的 RNA（siRNAs）、微 RNA（miRNAs）、转移 RNA（tRNAs）、核糖体 RNA（rRNAs）和 mRNAs 在内的所有 RNA 分子类别都通过脉管系统运输到远处的组织。虽然作为信号分子的移动 siRNAs 和 miRNAs 的功能已得到很好的证实，但我们对移动 mRNA 在受体细胞和组织中的功能以及它们如何被选择进行运输知之甚少。在黄瓜、南瓜、拟南芥和葡萄等多种植物中，多达数千种 mRNAs 被描述为远距离移动，通过嫁接接头长距离移动到不同的身体部位。在这篇综述中，我们概述了移动 RNA 的种类、促进 RNA 长距离运输的潜在机制，以及移动 RNA 在转录和翻译调控中的作用。此外，我们还针对移动编码蛋白的 mRNAs 的潜在功能及其特征和进化限制进行了探讨。
