Gunnera Cyanobacteria symbiosis

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Gunnera

Gunnera is the only genus in the family Gunneraceae. Gunnera, consisting of about 30-40 species, is a herbaceous flowering plant found in Central and South America, Africa, Madagascar, Tasmania, New Zealand and Hawaii [1].


Gunnera manicata is one of the largest species of Gunnera native to the Serra do Mar mountains of southeastern Brazil. Leaves range from 1.5 to 2.0 meters long [2] with an average diameter of 2.5m. Some leaves have been measured to be up to 3.3m across when cultivated [3]. In contrast, Gunnera magellanica is a species of Gunnera native to Chile, Argentina, the Falkland Islands, Peru, and Ecuador. The leaves of G. magellanica only grow 3-4 cm in diameter and leaf stalks reach 5-6 cm tall [4].


Gunnera manicata leaves measure 1.5 to 2.0 meters [1] while Gunnera magellanica leaves measure only 3 to 4 cm [2].
The phylogenic tree of the Family Gunneraceae, consisting of only one genus Gunnera.[3].


Cyanobacteria

Cyanobacteria are the largest phylum of Gram-positive prokaryotes on earth dating back to 3.5 billion years ago[5]. They evolved the ability to use photosynthesis to obtain their energy, making them different from other single celled organisms at the time [6]. By photosynthesizing, the Cyanobacteria produce oxygen as a byproduct. This is believed to have both helpe the bacteria successfully prosper because the environment in which they were developing was otherwise occupied by anaerobic bacteria and cause the Great Oxidation Event [7]. The Great Oxidation Event is where the earth first experiences a rise in the amount of oxygen in the atmosphere and oceans[8].


Many species of Cyanobacteria live in large colonies of cells ranging from hundreds to thousands of cells in a single colony [9]. These colonies are able to form filaments, sheets, or hollow spheres [10]. When too large, they can form harmful algal blooms that can cause great harm to the aquatic ecosystem and the surrounding area it lives [11]. Cyanobacteria can be found in almost any terrestrial or aquatic environment ranging from oceans and lakes to extremes like wet rocks in a desert or in the Antarctic [12]


Cyanobacteria are wide spread around the world, contributing to major global biogeochemical cycles like cellular death [13]. They also have been shown to be responsible for a large portion of the earth’s N2 and CO2 fixation. N2 fixation is a process where the Cyanobacteria can convert the nitrogen gas into ammonia, nitrites, and nitrates which can then be used by plants to make proteins and nucleic acids[14]. In CO2 fixation, Cyanobacteria have large proteins called carboxysomes which have been seen to take up inorganic carbon and efficiently “fix” it into organic compounds that can then be used by living organisms[15].

Gunnera and Cyanobacteria symbiosis

The filamentous cyanobacteria genus Nostoc has been observed to form colonies in both terrestrial and aquatic habitats. and screen damaging ultraviolet light. Nostoc has also been seen to screen damaging ultraviolet light and possesses the ability to fix atmospheric N2 [16]. For this reason, scientists believe several Gunnera species have developed a complex symbiotic relationship with Nostoc. This relationship is unique as it is the only known relationship between a cyanobacterium and an angiosperm.


The symbiosis takes place when the Nostoc bacteria enter into the Gunnera by way of specialized gland organs on the stems of the plants [17]. The glands secrete a solution that attracts the Nostoc [18]. Once in the organs, the Nostoc enters into the cells of the Gunnera where it produces N2-fixing cells [19]. These cells are known as heterocysts which are thick walled, specialized N-fixing cells [20].


Previous studies have revealed that Gunnera is unable to use nitrate because it lacks the enzyme nitrate reductase. Nostoc is able to fix the nitrogen to fill the needs of the Gunnera [21].


Conclusion

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References

  1. ↑ Gunneraceae: gunnera. Phylogeny of New Zealand Plants. (n.d.). Retrieved November 24, 2021, from https://plantphylogeny.landcareresearch.co.nz/webforms/viewtree.aspx?ObjectID=e6155e0d-5659-4813-86f7-70a5f1c250ca.
  2. ↑ Gunnera Explained. (n.d.). Retrieved November 24, 2021, from http://everything.explained.today/Gunnera/.
  3. ↑ BBC. (2011, October 14). Abbotsbury Gardens celebrates plant's 'monster' leaves. BBC News. Retrieved November 24, 2021, from https://www.bbc.com/news/uk-england-berkshire-15308919
  4. ↑ Söderbäck, E., Lindblad, P., & Bergman, B. (1990). Developmental patterns related to nitrogen fixation in the Nostoc-Gunnera magellanica Lam. symbiosis. Planta, 182(3), 355-362.
  5. ↑ Schopf, J. W., & Packer, B. M. (1987). Early Archean (3.3-billion to 3.5-billion-year-old) microfossils from Warrawoona Group, Australia. Science, 237(4810), 70-73.
  6. ↑ Sinha, R. P., & Häder, D. P. (2008). UV-protectants in cyanobacteria. Plant Science, 174(3), 278-289.
  7. ↑ Whitton, B. A. (Ed.). (2012). Ecology of cyanobacteria II: their diversity in space and time. Springer Science & Business Media.
  8. ↑ Lyons, T. W., Reinhard, C. T., & Planavsky, N. J. (2014). The rise of oxygen in Earth’s early ocean and atmosphere. Nature, 506(7488), 307-315.
  9. ↑ Tamulonis, C., Postma, M., & Kaandorp, J. (2011). Modeling filamentous cyanobacteria reveals the advantages of long and fast trichomes for optimizing light exposure. PLoS One, 6(7), e22084.
  10. ↑ Aguilera, A., Klemenčič, M., Sueldo, D. J., Rzymski, P., Giannuzzi, L., & Martin, M. V. (2021). Cell death in Cyanobacteria: current understanding and recommendations for a consensus on its nomenclature. Frontiers in Microbiology, 12, 416.
  11. ↑ Paerl, H. W., & Otten, T. G. (2013). Harmful cyanobacterial blooms: causes, consequences, and controls. Microbial ecology, 65(4), 995-1010.(Pearl and Otten)
  12. ↑ De Los Ríos, A., Grube, M., Sancho, L. G., & Ascaso, C. (2007). Ultrastructural and genetic characteristics of endolithic cyanobacterial biofilms colonizing Antarctic granite rocks. FEMS microbiology ecology, 59(2), 386-395.
  13. ↑ Aguilera, A., Klemenčič, M., Sueldo, D. J., Rzymski, P., Giannuzzi, L., & Martin, M. V. (2021). Cell death in Cyanobacteria: current understanding and recommendations for a consensus on its nomenclature. Frontiers in Microbiology, 12, 416.
  14. ↑ Adams, D. G., & Duggan, P. S. (2008). Cyanobacteria–bryophyte symbioses. Journal of Experimental Botany, 59(5), 1047-1058.
  15. ↑ Hill, N. C., Tay, J. W., Altus, S., Bortz, D. M., & Cameron, J. C. (2020). Life cycle of a cyanobacterial carboxysome. Science advances, 6(19), eaba1269.
  16. ↑ Dodds, W. K., Gudder, D. A., & Mollenhauer, D. (1995). The ecology of Nostoc. Journal of Phycology, 31(1), 2-18.
  17. ↑ BERGMAN, B., JOHANSSON, C., & SÖDERBÄCK, E. (1992). The Nostoc–Gunnera symbiosis. New Phytologist, 122(3), 379-400.
  18. ↑ Pawlowski, K., & Bergman, B. (2007). Plant symbioses with Frankia and cyanobacteria. In Biology of the Nitrogen Cycle (pp. 165-178). Elsevier.
  19. ↑ BERGMAN, B., JOHANSSON, C., & SÖDERBÄCK, E. (1992). The Nostoc–Gunnera symbiosis. New Phytologist, 122(3), 379-400.
  20. ↑ Borowitzka, M. A. (2018). Biology of microalgae. In Microalgae in health and disease prevention (pp. 23-72). Academic Press.
  21. ↑ Sprent, J.I. (2005). NITROGEN IN SOILS | Symbiotic Fixation. In Encyclopedia of Soils in the Environment(pp. 46-56). Elsevier.


Edited by Rachael Tomasko, student of Joan Slonczewski for BIOL 116 Information in Living Systems, 2021, Kenyon College.

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