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Open Access Methodology

Inflorescence stem grafting made easy in Arabidopsis

Nazia Nisar, Shelley Verma, Barry J Pogson and Christopher I Cazzonelli*

Author Affiliations

Australian Research Council Centre of Excellence in Plant Energy Biology, College of Medicine, Biology and Environment, Research School of Biology, The Australian National University, Canberra, ACT 0200, Australia

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Plant Methods 2012, 8:50  doi:10.1186/1746-4811-8-50

The electronic version of this article is the complete one and can be found online at: http://www.plantmethods.com/content/8/1/50


Received:17 September 2012
Accepted:17 December 2012
Published:19 December 2012

© 2012 Nisar et al.; licensee BioMed Central Ltd.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background

Plant grafting techniques have deepened our understanding of the signals facilitating communication between the root and shoot, as well as between shoot and reproductive organs. Transmissible signalling molecules can include hormones, peptides, proteins and metabolites: some of which travel long distances to communicate stress, nutrient status, disease and developmental events. While hypocotyl micrografting techniques have been successfully established for Arabidopsis to explore root to shoot communications, inflorescence grafting in Arabidopsis has not been exploited to the same extent. Two different strategies (horizontal and wedge-style inflorescence grafting) have been developed to explore long distance signalling between the shoot and reproductive organs. We developed a robust wedge-cleft grafting method, with success rates greater than 87%, by developing better tissue contact between the stems from the inflorescence scion and rootstock. We describe how to perform a successful inflorescence stem graft that allows for reproducible translocation experiments into the physiological, developmental and molecular aspects of long distance signalling events that promote reproduction.

Results

Wedge grafts of the Arabidopsis inflorescence stem were supported with silicone tubing and further sealed with parafilm to maintain the vascular flow of nutrients to the shoot and reproductive tissues. Nearly all (87%) grafted plants formed a strong union between the scion and rootstock. The success of grafting was scored using an inflorescence growth assay based upon the growth of primary stem. Repeated pruning produced new cauline tissues, healthy flowers and reproductive siliques, which indicates a healthy flow of nutrients from the rootstock. Removal of the silicone tubing showed a tightly fused wedge graft junction with callus proliferation. Histological staining of sections through the graft junction demonstrated the differentiation of newly formed vascular connections, parenchyma tissue and lignin accumulation, supporting the presumed success of the graft union between two sections of the primary inflorescence stem.

Conclusions

We describe a simple and reliable method for grafting sections of an Arabidopsis inflorescence stem. This step-by-step protocol facilitates laboratories without grafting experience to further explore the molecular and chemical signalling which coordinates communications between the shoot and reproductive tissues.

Keywords:
Grafting; Wedge; Plant development; Inflorescence stem; Systemic; Signal; Molecule; Transmission; Arabidopsis; Scion

Background

Grafting is a traditional method for uniting one part (scion) of a plant (e.g. shoot or bud) with the root system of another. It has become a fundamental method for studying physiological, genetic and molecular aspects of long distance signalling events. There are many grafting techniques described, of which some are widely used in agriculture as a mean to facilitate asexual propagation. Advantages are to induce dwarfing and fruitfulness, avoid juvenility, promote sturdiness [1,2] as well as facilitate domestication of both woody and non woody plant species [3,4]. In the laboratory, grafting for most dicot species is now a well-established practice widely used to study plant nutrition [5], disease resistance against phloem associated pathogens [6,7], apical dominance and shoot branching [8,9].

Grafting has provided a powerful approach to combine diverse genotypes and investigate the transport of various long-distance signalling molecules [8]. The technique of grafting has demonstrated that 1) the transfer of tuberigen stimulates tuberization in potato [10-12], 2) autoregulation of nodulation is regulated via long-distance shoot and root derived signals, [13-16], 3) allocation of nutrients by the Arabidopsis Na+ transporter AtHKT1 functions in the root to control Na+ accumulation in the shoot [17-20] and that the phloem mobile miRNA that acts as long-distance signal regulating phosphate homeostasis in Arabidopsis [18,19], 4) transport of phytohormone growth molecules such as the movement of cytokinin from roots to shoots [21] and translocation of strigolactone from root to shoot which inhibits shoot branching [22,23], 5) the movement of secondary metabolites such as alkaloids [24] and 6) mobile flowering signals synthesized in the leaves can stimulate flowering within the shoot apical meristem [25-28].

Hypocotyl micrografting techniques have been successfully used to study developmental and physiological processes between the root and shoot [2,8,29-31], while the inflorescence meristem grafting methods have generally been used to investigate the nature of signals coordinating floral reproductive growth [32-36]. Indeed small RNAs have been shown to move across the junctions from hypocotyl and inflorescence grafts, most likely via the plasmodesmata rather than the phloem [37-39]. Experiments investigating the movement of mobile signals that control apical dominance (cytokinins and auxin), nutrient uptake (phosphorus) and cellular differentiation (small RNAs) are key research areas that can benefit from the inflorescence grafting technique. Given that this technique investigates a post-floral transition, it provides a unique system to discover signals mediating reproductive development.”

This paper describes a protocol for efficient wedge-style grafting of the primary inflorescence scion to the rootstock. We define the location, timing and preparation of the floral stems for grafting. An inflorescence growth assay was developed to determine the healthiest of grafts. Histological studies confirmed the differentiation of vascular connections as well as a successful graft union.

Results and discussion

A robust and highly efficient grafting method for arabidopsis

Preliminary homografting experiments were carried out using young primary inflorescence stems of uniform age, length, and diameter using the model plant, Arabidopsis thaliana. Both horizontal [35] and wedge-style [34] grafting techniques proved less successful then previously reported. Difficulties were encountered in maintaining hydraulic turgor as well as providing structural support to the grafted stem sections. For the horizontal grafts we found that by sliding silicone tubing over the graft junction and sealing with either parafilm or Petroleum Jelly (Vaseline) provided structural support as well as minimise scion transpiration allowing reproductive tissues to survive until the graft union re-establishes xylem and phloem continuity. However, within one week of growth the grafted scions began to wilt showing signs of necrosis, most likely due to poor contact between the grafted stem sections. It is essential that sufficient contact between the stem of the scion and root stock is maintained in order to promote the development of vascular connections, which allow the flow of nutrients through the stem to the reproductive organs.

Next we performed the wedge-style graft, reported to have a much higher success rate, potentially due to greater contact area between tissues at the graft junction, but difficulties were encountered when attempting to stabilise the grafted stem sections with thin glass splints [34]. Instead, a 1.5 cm length of silicone tubing placed over the wedge provided excellent structural support to the primary inflorescence and ensured good contact at the junction of the wedge. The silicone tubing was flexible and did not appear to restrict inflorescence stem growth. The silicone supported graft junction was further sealed with parafilm to prevent desiccation and maintain turgor (Figure 1). Immediately following grafting the grafted scions began to wilt (Figure 2A) and within 24 hrs the grafted scions regain turgor and stand upright (Figure 2B, 1DAGr). Without any prior experience, a 35% success rate was achieved using this technique in a pilot experiment. Typically, greater than 87% (n = 103) success rates were achieved by several experienced researchers in our group, highlighting a very simple, efficient and robust wedge-style grafting technique (Figure 1).

thumbnailFigure 1. Schematic illustration displaying an Arabidopsis wedge grafting technique. (A) Horizontal cut of the floral stem. (B) The floral scion was trimmed to form a wedge and the floral stem stock vertically cut to form a donor wedge in which to insert the floral scion (C), before sliding a tightly fitted silicone tube (blue) over the wedge junction (D).

thumbnailFigure 2. Growth habits of grafted inflorescence stems from A. thaliana. Floral stem grafts wilt immediately after sealing the graft (A) and if successful recover within 24 hours by standing upright (B). Successful floral stem grafts will maintain shoot apical dominance (C; 7 DAGr) and develop extended cauline shoot branches (D; 14 DAGr) with healthy reproductive siliques (E; 22 DAGr). A grafted plant was pruned to remove all reproductive siliques and at the cauline nodes, new cauline leaves and shoots were produced leading to the formation of new reproductive siliques (F; 60 DAGr).

A non-destructive inflorescence growth assay for identifying healthy grafts

The success of grafting was determined by monitoring scion growth and development: processes that require the transport of water, nutrients and signalling molecules. Previously, grafting had been considered successful when scions remained alive on top of the rootstock [34]. Here we further redefine that a successful floral stem graft should 1) be able to maintain shoot apical dominance as evidenced by a taller primary stem (Figure 2C; 7 DAGr), 2) grow healthy cauline shoot branches which continue to develop (Figure 2D; 14 DAGr) and 3) produce fertile reproductive siliques (Figure 2E; 22 DAGr). The most definitive measure of success of a grafted plant is by pruning (i.e. remove cauline shoot branches and reproductive siliques), which promotes the growth of new cauline leaf and shoot tissues eventually leading to the formation of new reproductive siliques (Figure 2F; 60 DAGr).

We identified some “successful” grafts that remained viable, but, the scion stem failed to grow and maintain apical dominance, as evident by longer cauline branches relative to the primary rosette stem (Figure 3A; plants 13–15), which is indicative of an incomplete union. The number of cauline branches (~2-3) was similar for the “successful” grafts (Figure 3A). Therefore, we devised a non-destructive growth method for revealing fully successful and healthy grafted plants by quantifying the distance between the oldest (lowest on the scion) cauline node and top of the primary inflorescence scion stem. We measured the inflorescence stem height from 15 healthy and “successful” looking homografted plants (22 and 26 DAGr) and observed 12 grafted plants that showed sufficient growth of the scion stem, and also maintained control over apical dominance, as evidenced by shorter cauline shoot branches compared to the primary stem (Figure 3B). However, only 10 of the apically dominant grafted plants continued shoot growth between 22 and 26 days after grafting (Figure 3B), revealing that this non-destructive growth assay is a viable means by which to select the best grafted plants suitable for physiological and molecular investigations.

thumbnailFigure 3. Evaluation of the growth status of successful grafts. (A) Images of 15 healthy grafted plants showing a range in inflorescence growth habits. (B) Inflorescence stem height (cm) of 15 grafted plants measured 22 and 26 DAGr. The stem height reflects the distance between the first cauline node and top of the primary inflorescence flower. The numbers below the images (A) and on the x-axis of the graph (B) identify the grafted plant being tested.

Anatomy of graft union formation at the wedge junction

We analysed the integrity of graft union formation to confirm that vascular connections were established between the scion and stem from the root stock. The formation of regenerative xylem vessels following wounding occurs mostly in young inflorescence stems (e.g. 2 to 4 day-old) [34] and indeed the lower section (2–4 cm above the rosette) of a young primary inflorescence stem was found to best suited for wedge grafting. Removal of the parafilm covering the silicone tube revealed a sealed graft junction (Figure 4A) that remained tightly connected even after the silicone tube was removed (Figure 4B). Callus proliferation was clearly observed surrounding the wedge junction providing a good indication of regenerative growth (Figure 4B). Histologic analysis of a longitudinal section through the wedge graft showed the differentiation of new vascular tissues within the scion, which were associated with lignin accumulation (blue-green cells) and as well as a tight vascular graft union formation between the scion and the stock (Figure 4C). Transverse sections through the wedge graft revealed a small deposit of lignin at the tip of the scion graft (Figure 5A and 5B), formation of a necrotic plate (Figure 5C, 5D), differentiation of parenchymal cells and vascular tissues (Figure 5D) when compared to a section of wild type stem (Figure 5E). The histological data supports the formation of a successful graft union.

thumbnailFigure 4. Longitudinal views of a grafted inflorescence A. thaliana stem. A floral stem graft showing expansion of the silicone tubing surrounding the wedge junction (A) and grafted stem tissues fused tightly in the absence of the silicone tubing (B). (C and D) A longitudinal section through the floral stem graft shows lignified tissues (blue-green) and non-lignified (purple-red) tissues surrounding the grafted wedge.

thumbnailFigure 5. Cross-section of an inflorescence stem of A. thaliana stained with toluidine blue. (A) Side view of the wedge graft junction showing the positions of 4 transverse sections. (B-E) Transverse sections taken from the bottom (B), middle (C) and top (D) of the wedge-graft as well as from an ungrafted floral stem section taken above the wedge-graft (E).

In summary, we have developed a robust grafting method for Arabidopsis that is efficient and easily scaled for high throughput studies. A series of tips ensure a high success rate (Table 1) and the development of the non-destructive inflorescence growth assay provides a simple measure by which to determine the healthiest and most successful grafted plants amenable to physiological, metabolic and molecular studies interested in dissecting the signalling pathways controlling reproductive growth in Arabidopsis.

Table 1. Technical tricks for successful wedge-style inflorescence grafting in Arabidopsis

Materials

Planting and growth conditions

Dried seeds were sown onto DEBCO seed raising mixture, fertilized with 3 g/L of mini Osmocote and cold-stratified at 4°C in the dark for three days to synchronise germination. Seeds were germinated in the light (16 hrs, 21°C, 55% humidity, 150 μmol m-2 s-1 irradiance), irrigated twice a week with water and grown under these conditions unless otherwise stated. In order to synchronise inflorescence meristem initiation, germinated seedlings (7 DAG) were vernalised for four weeks at 4°C before returning seedlings to the growth conditions described above. Vernalization may not need to be performed if all plant genotypes flower simultaneously. Reducing the day length will slow growth and produce larger rosettes with thicker inflorescence meristems, thereby facilitating preparation of the scion and root stock for wedge style grafting.

Histology and microscopy

Plant samples were stained with aqueous 0.01% Toluidine Blue-O for 1 minute and rinsed in water. Fresh tissue specimens were placed on glass slides, covered with a glass coverslip and water used to fill the airspaces and maintain cell turgor. Slides were examined under a Leica MZ16FA Fluorescence Stereomicroscope and representative sections photographed.

Reagents and consumables

· Double edge safety razor blades (fine stainless steel, platinum coated to enhance sharpness)

· 1 cc/mL Plastic syringe

· Silicone Tubing 1.5 mm ID × 2.3 mm OD

· Silicone Tubing 2.0 mm ID × 2.8 mm OD

· Silicone Tubing 2.5 mm ID × 3.3 mm OD

· Silicone Tubing 3.0 mm ID × 3.8 mm OD

· Petri dishes

· Clear plastic humidity chamber

· Plastic paraffin film (Parafilm)

· Sterile water

Protocol

Arabidopsis wedge style grafting

Grafting was performed when the primary inflorescence meristem reached a height of 5 to 10 cm above the rosette and floral buds became clearly visible). It is important to grow a large number of plants (>30) in order to ensure that floral stems of a similar thickness can be matched.

1) Remove the floral bolt from the rootstock (leave 3-5 cm of the inflorescence stem on the root stock) by making a horizontal cut (with a two edge razor blade) and immediately place the scion in a petri dish containing water to prevent air entering the vascular stream. If performing many grafts simultaneously, place a small droplet of water on the rootstock stem to prevent any desiccation.

2) Place a 1.5 cm long section of silicone tubing (1–4 mm internal diameter depending upon thickness of floral bolt) over the shoot stump on the root stock. The tubing should have a slightly larger internal diameter than the stem to be grafted allowing the tubing to slip up over the graft junction.

3) Make a 1 cm long median incision along the length of the shoot stump on the root stock and immediately add a drop of water inside the incision using a syringe, creating a v-shape wedge. This will keep the incision moist and promote an efficient union between the scion and rootstock.

4) Cut the horizontally-severed floral stem into a long v-shape wedge under water and position inside the incision of the root stock stem. The wedge graft will provide greater contact between vascular as well as improve surface tension.

5) Slide the silicone tubing over the wedge graft to secure contact between the scion and root stock. The silicone tubing will provide vertical support to the upper floral scion. Use a syringe to inject water above the silicone tubing and onto the floral stem stump in order to prevent desiccation.

6) The graft junction was further sealed by wrapping with parafilm (1 cm above and below the silicone tubing) to maintain hydraulic turgor and prevent desiccation. The parafilm needs to be stretched before application to generate a slightly adhesive surface making it easier to seal around the graft junction.

7) Cover the grafted plants with a clear plastic humidity chamber in order to maintain a humid environment. If you have a growth chamber, adjust to 70% humidity.

8) Water the grafted plants regularly to help maintain a humid environment and begin to acclimate to normal growing conditions within two weeks of performing the grafts.

Abbreviations

DAG: Days after germination; DAGr: Days after grafting; ID: Internal diameter; OD: Outside diameter.

Competing interests

The authors declare that they have no competing interests.

Authors’ contributions

CIC and BJP planned the research. NN, SV and CIC developed the grafting techniques and contributed to writing the manuscript as well as preparing figures. All authors read and approved the final manuscript.

Acknowledgements

The research was supported by the Australian Research Council (ARC) Centre of Excellence in Plant Energy Biology (CE0561495).

References

  1. Mudge K: A history of grafting.

    Horticultural Rev 2009, 35:437-493. OpenURL

  2. Yin H, Yan B, Sun J, Jia P, Zhang Z, Yan X, Chai J, Ren Z, Zheng G, Liu H: Graft-union development: a delicate process that involves cell to cell communication between scion and stock for local auxin accumulation.

    J Exp Bot 2012, 63:4219-4232. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  3. Toogood A, Anderson P: American horticultural society plant propagation: the fully illustrated plant-by-plant manual of practical techniques. Alexandria, VA: American Horticultural Society; 1999. OpenURL

  4. Turnbull CG: Grafting as a research tool.

    Methods Mol Biol 2010, 655:11-26. PubMed Abstract | Publisher Full Text OpenURL

  5. Jayawickrama KJS, McKeand SE, Jett JB, Young E: Rootstock and scion effects on carbohydrates and mineral nutrients in loblolly pine.

    Can J Forest Res 1992, 22:1966-1973. Publisher Full Text OpenURL

  6. Bertaccini A, Bellardi MG: A rhabdovirus inducing vein yellowing in croton.

    Plant Path 1992, 41:79-82. Publisher Full Text OpenURL

  7. Cohen R, Horev C, Burger Y, Shriber S, Hershenhorn J, Katan J, Edelstein M: Horticultural and pathological aspects of fusarium wilt management using grafted melons. Alexandria, VA, ETATS-UNIS: American Society for Horticultural Science; 2002. OpenURL

  8. Turnbull CGN, Booker JP, Leyser HMO: Micrografting techniques for testing long-distance signalling in arabidopsis.

    Plant J 2002, 32:255-262. PubMed Abstract | Publisher Full Text OpenURL

  9. Mapelli S, Kinet JM: Plant growth regulator and graft control of axillary bud formation and development in the TO-2 mutant tomato.

    Plant Growth Regul 1992, 11:385-390. Publisher Full Text OpenURL

  10. Ewing EE, Struik PC: Tuber formation in potato: Induction, initiation, and growth.

    Hort Rev 1992, 14:89-197. OpenURL

  11. Martinez-Garcia JF, Virgos-Soler A, Prat S: Control of photoperiod-regulated tuberization in potato by the arabidopsis flowering-time gene CONSTANS.

    P Natl Acad Sci USA 2002, 99:15211-15216. Publisher Full Text OpenURL

  12. Navarro C, Abelenda JA, Cruz-Oro E, Cuellar CA, Tamaki S, Silva J, Shimamoto K, Prat S: Control of flowering and storage organ formation in potato by flowering locus T.

    Nature 2011, 478:119-122. PubMed Abstract | Publisher Full Text OpenURL

  13. Okamoto S, Ohnishi E, Sato S, Takahashi H, Nakazono M, Tabata S, Kawaguchi M: Nod factor/nitrate-induced CLE genes that drive HAR1-mediated systemic regulation of nodulation.

    Plant Cell Physiol 2009, 50:67-77. PubMed Abstract | Publisher Full Text OpenURL

  14. Caetano-Anolles G, Gresshoff PM: Plant genetic control of nodulation.

    Annu Rev Microbiol 1991, 45:345-382. PubMed Abstract | Publisher Full Text OpenURL

  15. Delves AC, Mathews A, Day DA, Carter AS, Carroll BJ, Gresshoff PM: Regulation of the soybean-rhizobium nodule symbiosis by shoot and root factors.

    Plant Physiol 1986, 82:588-590. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  16. Searle IR, Men AE, Laniya TS, Buzas DM, Iturbe-Ormaetxe I, Carroll BJ, Gresshoff PM: Long-distance signaling in nodulation directed by a CLAVATA1-like receptor kinase.

    Science 2003, 299:109-112. PubMed Abstract | Publisher Full Text OpenURL

  17. Balachandran S, Hull RJ, Vaadia Y, Wolf S, Lucas WJ: Alteration in carbon partitioning induced by the movement protein of tobacco mosaic virus originates in the mesophyll and is independent of change in the plasmodesmal size exclusion limit.

    Plant Cell Environ 1995, 18:1301-1310. Publisher Full Text OpenURL

  18. Lin S-I, Chiang S-F, Lin W-Y, Chen J-W, Tseng C-Y, Wu P-C, Chiou T-J: Regulatory network of MicroRNA399 and PHO2 by systemic signaling.

    Plant Physiol 2008, 147:732-746. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  19. Pant BD, Buhtz A, Kehr J, Scheible W-R: MicroRNA399 is a long-distance signal for the regulation of plant phosphate homeostasis.

    Plant J 2008, 53:731-738. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  20. Rus A, Baxter I, Muthukumar B, Gustin J, Lahner B, Yakubova E, Salt DE: Natural variants of AtHKT1 enhance Na + accumulation in Two wild populations of arabidopsis.

    PLoS Genet 2006, 2:e210. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  21. Beveridge CA: Axillary bud outgrowth: sending a message.

    Curr Opin Plant Biol 2006, 9:35-40. PubMed Abstract | Publisher Full Text OpenURL

  22. Leyser O: Regulation of shoot branching by auxin.

    Trends Plant Sci 2003, 8:541-545. PubMed Abstract | Publisher Full Text OpenURL

  23. Foo E, Turnbull CG, Beveridge CA: Long-distance signaling and the control of branching in the rms1 mutant of pea.

    Plant Physiol 2001, 126:203-209. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  24. Wilson PMW: Distribution of ‘Solanaceous’ alkaloids in some new graft combinations.

    New Phytol 1952, 51:260-262. Publisher Full Text OpenURL

  25. Zeevaart JAD: Florigen coming of age after 70 years.

    Plant Cell 2006, 18:1783-1789. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  26. Mylne JS, Wigge PA: Plant chemical biology: florigen takes two to tango.

    Nat Chem Biol 2011, 7:665-666. PubMed Abstract | Publisher Full Text OpenURL

  27. An H, Roussot C, Suarez-Lopez P, Corbesier L, Vincent C, Piñeiro M, Hepworth S, Mouradov A, Justin S, Turnbull C, Coupland G: CONSTANS acts in the phloem to regulate a systemic signal that induces photoperiodic flowering of arabidopsis.

    Development 2004, 131:3615-3626. PubMed Abstract | Publisher Full Text OpenURL

  28. Corbesier L, Vincent C, Jang S, Fornara F, Fan Q, Searle I, Giakountis A, Farrona S, Gissot L, Turnbull C, Coupland G: FT protein movement contributes to long-distance signaling in floral induction of arabidopsis.

    Science 2007, 316:1030-1033. PubMed Abstract | Publisher Full Text OpenURL

  29. Bainbridge K, Bennett K, Turnbull C, Leyser O: Grafting.

    Methods Mol Biol 2006, 323:39-44. PubMed Abstract | Publisher Full Text OpenURL

  30. Cazzonelli C, Cuttriss A, Cossetto S, Pye W, Crisp P, Whelan J, Finnegan E, Turnbull C, Pogson B: Regulation of carotenoid composition and shoot branching in arabidopsis by a chromatin modifying histone methyltransferase, SDG8.

    Plant Cell 2009, 21:39-53. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  31. Hirsch J, Misson J, Crisp PA, David P, Bayle V, Estavillo GM, Javot H, Chiarenza S, Mallory AC, Maizel A, et al.: A novel fry1 allele reveals the existence of a mutant phenotype unrelated to 5’- > 3’ exoribonuclease (XRN) activities in arabidopsis thaliana roots.

    PLoS One 2011, 6:e16724. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  32. Ayre B, Turgeon R: Graft transmission of a floral stimulant derived from CONSTANS1.

    Plant Physiol 2004, 135:2271-2278. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  33. Chen A, Komives EA, Schroeder JI: An improved grafting technique for mature arabidopsis plants demonstrates long-distance shoot-to-root transport of phytochelatins in arabidopsis.

    Plant Physiol 2006, 141:108-120. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  34. Flaishman M, Loginovsky K, Golobowich S, Lev-Yadun S: Arabidopsis thaliana as a model system for graft union development in homografts and heterografts.

    J Plant Growth Regul 2008, 27:231-239. Publisher Full Text OpenURL

  35. Rhee S, Somerville C: Flat-surface grafting in arabidopsis thaliana.

    Plant Molec Biol Rep 1995, 13:118-123. Publisher Full Text OpenURL

  36. Tsukaya H, Naito S, Rédei G, Komeda Y: A new class of mutations in arabidopsis thaliana, acaulis1, affecting the development of both inflorescences and leaves.

    Development 1993, 118:751-764. OpenURL

  37. Molnar A, Melnyk CW, Bassett A, Hardcastle TJ, Dunn R, Baulcombe DC: Small silencing RNAs in plants are mobile and direct epigenetic modification in recipient cells.

    Science 2010, 328:872-875. PubMed Abstract | Publisher Full Text OpenURL

  38. Liang D, White RG, Waterhouse PM: Gene silencing in arabidopsis spreads from the root to the shoot, through a gating barrier, by template-dependent, nonvascular, cell-to-cell movement.

    Plant Physiol 2012, 159:984-1000. PubMed Abstract | Publisher Full Text | PubMed Central Full Text OpenURL

  39. Haywood V, Yu T-S, Huang N-C, Lucas WJ: Phloem long-distance trafficking of gibberellic acid-insensitive RNA regulates leaf development.

    Plant J 2005, 42:49-68. PubMed Abstract | Publisher Full Text OpenURL