Root-to-Shoot Long-Distance Mobile miRNAs Identified from Nicotiana Rootstocks.

Zhuying Deng,Luping Li,Yongzhong Xing,Zhipeng Wang,Huiyan Wu,Dacheng Liang,Chengdao Li,Dongyi Li,Wenya Yuan

doi:10.3390/ijms222312821

Abstract

Root-derived mobile signals play critical roles in coordinating a shoot’s response to underground conditions. However, the identification of root-to-shoot long-distance mobile signals has been scant. In this study, we aimed to characterize root-to-shoot endogenous mobile miRNAs by using an Arabidopsis/Nicotiana interfamilial heterograft in which these two taxonomically distant species with clear genetic backgrounds had sufficient diversity in differentiating miRNA sources. Small RNA deep sequencing analysis revealed that 82 miRNAs from the Arabidopsis scion could travel through the graft union to reach the rootstock, whereas only a very small subset of miRNA (6 miRNAs) preferred the root-to-shoot movement. We demonstrated in an ex vivo RNA imaging experiment that the root-to-shoot mobile Nb-miR164, Nb-miR395 and Nb-miR397 were targeted to plasmodesmata using the bacteriophage coat protein MS2 system. Furthermore, the Nb-miR164 was shown to move from the roots to the shoots to induce phenotypic changes when its overexpressing line was used as rootstock, strongly supporting that root-derived Nb-miR164 was able to modify the scion trait via its long-distance movement.

Highlights

To stringently characterize the small RNAs that move from root to shoot, we adopted hypocotyl grafting, in which the graft union occurred at the hypocotyl region of At and
We found that the life span was extensively extended in the At/Nb grafts [23], and we hypothesized that any small RNAs from the rootstock could partially represent contributing factors to the observed phenotypic changes
We collected the samples at the mature stage of the At/Nb graft or 90 days after grafting (DAG) for small

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. One of the most fascinating aspects of plant grafting is the movement of macromolecules between a scion and rootstock (e.g., small RNA-mediated long-distance silencing movement [1,2], protein shuttling [3] and genetic material transfer [4,5,6,7,8]). The macromolecule movement may occur locally through cell-to-cell transfer via plasmodesmata (PD) or systematically through vasculature-mediated inter-tissue translocation. There are two specialized vascular tissues, namely the phloem and xylem, that usually serve as the superhighway for the long-distance transport of water, photoassimilates, nutrients, minerals and other signaling molecules. Emerging studies show that macromolecules are moving through these superhighways.

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