Plant Chimaeras and Mosaics


Plant chimaeras and mosaics are not only found in our gardens as variegated ornamentals. They also constitute valuable research tools with a range of applications in developmental and molecular biology. For example, much of our knowledge about the development of the shoot and root apical meristems is derived from studying patterns of variegation, and where patterns persist throughout the plant, deductions can be made as to the fate of individual meristematic cells and the number and arrangement of initial cells giving rise to a variety of plant organs or structures. At a molecular level, defined sectors can shed light on the cell autonomy of a certain trait, inform us about the propagation of molecular signals and indeed allow us to directly compare genetically distinct tissue sectors in an attempt to determine specific gene function.

Key Concepts:

  • Plant chimaeras comprise cells of distinct genomes, whereas in genetic mosaics, cells of different genotypes derived from the same zygote.

  • Cells with different genotypes or even from different species can communicate to form functional meristems and other tissues.

  • Continuous persistent sectors throughout a plant can be explained by a mosaic shoot apical meristem and can be used to create ‘developmental fate maps’.

  • The fate of most plant cells is determined late in development by their position rather than by their ancestry.

  • Sector boundary analysis is used to identify the number of cells set aside as progenitors of an organ.

  • Mosaic plants are used to analyse where a molecular signal originates and how it is propagated.

  • Sector analysis provides clues about the cell autonomy of a trait as well as specific gene function.

Keywords: chimaeras; genetic mosaics; shoot apical meristem; fate maps; cell lineage; sector analysis

Figure 1.

Variegated forms of (a) Hedera (ivy) and (b) Tradescantia (spiderwort).

Figure 2.

Schematic representation of shoot apical meristems comprising sectors and cell layers of different genetic make‐up and resulting leaf variegation (see text for explanations). (a) Sectorial chimaera (the three meristematic cell layers are indicated). (b) Periclinal chimaera. (c) Mericlinal chimaera.

Figure 3.

Sectored shoot and inflorescence of Arabidopsis thaliana as used by Bossinger and Smyth to study initiation patterns of flower and floral organ development (chlorophyll removed). Blue sectors are indicative of expression of the bacterial uidA reporter gene visualised by β‐glucuronidase (GUS) staining.

Figure 4.

Cross‐section (a) and schematic representation (b) of young poplar stem showing a genetically transformed tissue sector (blue staining) extending from the pith to the periderm. This sector can be interpreted as having derived from a single transformed initial. As it includes both xylem and phloem, it must have originated before the differentiation of these tissues from the procambium. Exclusion of pith and periderm from the sectored zone means that at the time of transformation, three distinct tissue layers existed in the developing shoot apical meristem. The stained sector occupies approximately 1/24th of the stem circumference, indicating that at the time of transformation and at this level of the developing apex some 24 procambial initials were arranged in a ring around a central pith surrounded by developing epidermal tissue (Spokevicius et al., ).



Baur E (1909) Das Wesen der Erblichkeitsverhältnisse der varietates albomarginatae hort. von Pelargonium zonale. Zeitschrift für Vererbungslehre 1: 330–351.

Bossinger G, Maddaloni M, Motto M and Salamini F (1992) Formation and cell lineage patterns of the shoot apex of maize. Plant Journal 2: 311–320.

Bossinger G and Smyth DR (1996) Initiation patterns of flower and floral organ development in Arabidopsis thaliana. Development 122: 1093–1102.

Christianson ML (1986) Fate map of the organizing shoot apex in Gossypium. American Journal of Botany 73: 947–958.

Dawe RK and Freeling M (1992) The role of initial cells in maize anther morphogenesis. Development 116: 1077–1085.

Furner IJ and Pumfrey JE (1992) Cell fate in the shoot apical meristem of Arabidopsis thaliana. Development 115: 755–764.

Fusaro AF, Matthew L, Smith NA et al. (2006) RNA interference‐inducing hairpin RNAs in plants act through the viral defence pathway. EMBO Reports 7: 1168–1175.

Hake S and Freeling M (1986) Analysis of genetic mosaics shows that the extra epidermal cell divisions in Knotted mutant maize plants are induced by adjacent mesophyll cells. Nature 320: 621–623.

Hantke SS, Carpenter R and Coen ES (1995) Expression of floricaula in single cell layers of periclinal chimeras activates downstream homeotic genes in all layers of floral meristems. Development 121: 27–35.

Jackson D, Veit B and Hake S (1994) Expression of maize Knotted1 related homeobox genes in the shoot apical meristem predicts patterns of morphogenesis in the vegetative shoot. Development 120: 405–413.

Merriam JR (1978) Estimating primordial cell numbers in Drosophila imaginal discs and histoblasts. In: Gehring WJ (ed.) Genetic Mosaics and Cell Differentiation, pp. 1–28. New York: Springer.

Poethig RS (1987) Clonal analysis of cell lineage patterns in plant development. American Journal of Botany 74: 581–594.

Satina S, Blakeslee AF and Avery AG (1940) Demonstration of the three germ layers in the shoot apex of Datura by means of induced polyploidy in periclinal chimeras. American Journal of Botany 27: 895–905.

Scheres B, Wolkenfelt H, Willemsen V et al. (1994) Embryonic origin of the Arabidopsis primary root and root meristem initials. Development 120: 2475–2487.

Spena A and Salamini F (1995) Genetic tagging of cells and cell layers for studies of plant development. Methods in Cell Biology 49: 331–354.

Spokevicius AS, Van Beveren KS and Bossinger G (2006) Agrobacterium mediated transformation of dormant lateral buds in poplar trees reveals developmental patterns in secondary stems. Functional Plant Biology 33: 133–139.

Szymkowiak EJ and Sussex IM (1992) The internal meristem layer (L3) determines floral meristem size and carpel number in tomato periclinal chimeras. Plant Cell 4: 1089–1100.

Szymkowiak EJ and Sussex IM (1996) What chimeras can tell us about plant development. Annual Review of Plant Physiology and Plant Molecular Biology 47: 351–376.

Tilney‐Bassett RAE (1986) Plant Chimeras. London: Edward Arnold.

Winkler H (1907) Über Pfropfbastarde und pflanzliche Chimären. Berichte der deutschen botanischen Gesellschaft 25: 568–576.

Further Reading

Dawe RK and Freeling M (1991) Cell lineage and its consequences in higher plants. Plant Journal 1: 3–8.

Dolan L, Duckett CM, Grierson C et al. (1994) Clonal relationships and cell patterning in the root epidermis of Arabidopsis. Development 120: 2465–2474.

Irish VF (1991) Cell lineage in plant development. Current Opinion in Genetics & Development 1: 169–173.

Irish VF and Sussex IM (1992) A fate map of the Arabidopsis embryonic shoot apical meristem. Development 115: 745–753.

Jegla DE and Sussex IM (1989) Cell lineage patterns in the shoot meristem of the sunflower embryo in the dry seed. Developmental Biology 131: 215–225.

Klekowski EJ Jr and Kazarinowa‐Fukshansky N (1984a) Shoot apical meristems and mutation: fixation of selectively neutral cell genotypes. American Journal of Botany 71: 22–27.

Klekowski EJ Jr and Kazarinowa‐Fukshansky N (1984b) Shoot apical meristems and mutation: selective loss of disadvantageous cell genotypes. American Journal of Botany 71: 28–34.

Langdale JA, Lane B, Freeling M and Nelson T (1989) Cell lineage analysis of maize bundle sheath and mesophyll cells. Developmental Biology 133: 128–139.

McDaniel CN and Poethig RS (1988) Cell‐lineage patterns in the shoot apical meristem of the germinating maize embryo. Planta 175: 13–22.

Nesbitt MN and Gartler SM (1971) The application of genetic mosaicism to developmental problems. Annual Review of Genetics 5: 143–162.

Poethig RS (1989) Genetic mosaics and cell lineage analysis in plants. Trends in Genetics 5: 273–277.

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Bossinger, Gerd, and Spokevicius, Antanas V(Feb 2011) Plant Chimaeras and Mosaics. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0002090.pub2]