A Sequential Three-Phase Pathway Constitutes Tracheary Element Connection in the Arabidopsis/Nicotiana Interfamilial Grafts.

Zhuying Deng,Tianlin Jin,Mi Wang,Tingting Cai,Huiyan Wu,Mengting Jiang,Dacheng Liang

doi:10.3389/fpls.2021.664342

Abstract

Scion-rootstock union formation is a critical step toward the functional assemblage of heterogeneous plants. Interfamilial scion-rootstock interaction often results in graft incompatibility during the assemblage process, and the underlying mechanisms are largely unknown. In this study, we reported that tracheary element (TE) remodeling, including TE segmentation and deformation, rather than de novo formation from callus or adjacent tissues, took place at the early stage of grafting interface between Arabidopsis thaliana and Nicotiana benthamiana (At/Nb). Following cellular deposits, the short TEs from both partners were overlapping, dependent on the homogeneity of contacting TEs, with each other. Without overlapping, the TEs at the interface would grow laterally, and the TEs above and below the interface would undergo self-fusion to form insulating spiraling bundles. Finally, the overlapping TEs constituted a continuous network through alignment. Our results provide a definitive framework for the critical process of TE behavior in the At/Nb distant grafts, including (1) segmentation and/or deformation, (2) matching, overlapping, and cellular deposits, and (3) aligning or spiraling. These insights might guide us in the future into constructing more compatible distant grafts from the perspective of TE homogeneity.

Highlights

Grafting is an ancient technique that allows an artificial combination of two different parts of the plants into a living symbiont and has been widely applied in horticultural and biological research
To understand how compatibility/incompatibility arose from the same heterografting combination, we focused on examining the behavior of tracheary element (TE) at the grafting union in both compatible and incompatible grafts
Adventitious roots first emerged from a hypocotyl tissue at about 7–10 days after grafting (DAG)

Summary

Introduction

Grafting is an ancient technique that allows an artificial combination of two different parts of the plants (rootstock and scion) into a living symbiont and has been widely applied in horticultural and biological research. Cotyledon grafting showed that a wild-type (WT) cotyledon, as a source of florigen, can rescue the late flowering phenotype of the ft-10 mutant by supplying the mobile FLOWERING LOCUS T (FT) protein (Yoo et al, 2013). Grafting in the hypocotyl tissue is a good way to demonstrate root-to-shoot signaling, e.g., long-distance mobile silencing (Brosnan et al, 2007; Liang et al, 2012), root-to-shoot signals for branching (Turnbull et al, 2002), and root-derived bps signaling for regulating shoot development (Van Norman et al, 2004). The grafting technique is widely applied for different purposes, the critical principle underlying grafting compatibility is poorly understood

Methods

Results

Discussion

Conclusion