Messenger RNA exchange between scions and rootstocks in grafted grapevines

Abstract

BackgroundGrafting has been widely practiced for centuries in the propagation and production of many vegetable and fruit species. However, the underlying molecular and genetic mechanisms for how the graft partners interact with each other to produce a successful graft remain largely unknown. We hypothesized that genome-wide mRNA exchanges, which were recently documented in grafted model plant species, are a general phenomenon widely present in grafted plants, including those in vegetable and fruit species, and have specific genotype- and environment-dependent characteristics modulating plant performance.MethodsUsing diagnostic SNPs derived from high throughput genome sequencing, we identified and characterized the patterns of genome-wide mRNA exchanges across graft junctions in grafted grapevines grown in the in vitro and field conditions.ResultsWe identified more than 3000 genes transporting mRNAs across graft junctions. These genes were involved in diverse biological processes and those involved in basic cellular, biosynthetic, catabolic, and metabolic activities, as well as responses to stress and signal transduction, were highly enriched. Field-grown mature grafts had much fewer genes transmitting mRNAs than the in vitro young grafts (987 vs. 2679). These mobile mRNAs could move directionally or bi-directionally between scions and rootstocks. The mRNA transmission rates of these genes were generally low, with 65 % or more having transmission rates lower than 0.01. Furthermore, genotypes, graft combinations and growth environments had impact on the directions of mRNA movement as well as the numbers and species of mRNAs being exchanged. Moreover, we found evidence for the presences of both passive and selective mechanisms underlying long distance mRNA trafficking in grafted grapevines.ConclusionsWe extended the studies of mRNA exchanges in model species to grapevines and demonstrated that genomic-scale mRNA exchange across graft junctions occurred in grapevines in a passive or genotype and environment-dependent manner.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-015-0626-y) contains supplementary material, which is available to authorized users.

PlaMoM: a comprehensive database compiles plant mobile macromolecules

“…Currently, PlaMoM includes 672 identified mobile ncRNAs (∼3.7%), 16 928 mobile mRNAs (∼94.1%) and 389 mobile proteins (∼2.2%). The mobile macromolecules currently cover 14 different species and ecotypes, namely A. thaliana Col-0, A. thaliana PED (13), Apium graveolens (celery) (15), Antirrhinum majus (snapdragon) (16), Ricinus communis (castor bean) (17), Cucumis melo (melon) (18), Citrullus lanatus (watermelon) (19), Cucumis sativus (cucumber) (19), Cucurbita maxima (pumpkin) (20), Cucurbita moschata (winter squash) (21), Vitis spp (grapevine species) (22), Oryza sativa (rice) (23), Solanum lycopersicum (tomato) (24) and Solanum tuberosum (potato) (11). Identification of the mobile macromolecules was based on different experimental methods, such as analysis of the phloem exudate/sap (15,17,18,25,26), the presence of distinguishable transcripts found in parasitic plants and their host plants (13,14) or by single nucleotide polymorphisms (SNPs) in mRNAs from heterografted plants or from grafted mutant/wild-type plants (13,22,27,28).…”

tRNA-Related Sequences Trigger Systemic mRNA Transport in Plants

“…While the functional role of many mobile mRNAs in distant tissues remains to be elucidated, evidence supports the notion that trafficking of small si/miRNAs and large mRNAs via the phloem plays an important role in regulating plant development (Lucas et al, 2001). A surprisingly high number of mRNAs can be found in phloem exudates (Guo et al, 2013) and move across graft junctions (Thieme et al, 2015;Yang et al, 2015), but no general and easily predictable RNA motif or conserved sequence mediating mobility could be identified in the graftmobile transcript populations (Calderwood et al, 2016). However, our data suggest that a significant fraction of mobile mRNAs carries a TLS motif potentially mediating mobility across graft junctions.…”

“…On the one hand, conserved and, thus, predictive mRNA motifs have not been described for known graftmobile mRNA populations (Guo et al, 2013;Thieme et al, 2015;Yang et al, 2015). On the other hand, recent work in potato showed that the 39 untranslated region (UTR) of the phloemmobile transcript BEL5 supports mRNA stability and trafficking into roots, where BEL5 protein initiates tuber formation (Banerjee et al, 2009;Cho et al, 2015).…”

Comparative Proteomic Analysis of the Graft Unions in Hickory (Carya cathayensis) Provides Insights into Response Mechanisms to Grafting Process

“…In grafted grapevines, nearly half of the transmitting genes observed in in vitro grafts (47.4%) were related to the ‘cellular metabolic process’ (Yang et al, 2015). The GO term classification suggested that the DEPs were probably associated with ‘catalytic activity’ (41.0%) and ‘metabolic process’ (40.0%), suggesting that metabolism was involved in the hickory grafting responses ( Figure 2A ).…”