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Cited by 112Plant Molecular Biology ResearchPlant tissue culture and regenerationHistory of Science and Medicine

1955: Kinetin arrives. The 50th anniversary of a new plant hormone

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Amasino, Richard·2005·Plant Physiology
DOI 10.1104/pp.104.900160PMC PMC1176392
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Abstract

Fifty years ago, scientists from the Botany and Biochemistry departments at the University of Wisconsin announced the isolation, crystallization, characterization, and synthesis of 6-furfurylaminopurine (Miller et al., 1955a, 1955b, 1956), a plant hormone in a class now referred to as cytokinins (Skoog et al., 1965). They proposed the trivial name kinetin for this substance, and described its ability to promote cell division in test tissues from tobacco (Nicotiana tabacum). The discovery of kinetin marked the culmination of several years of research on a variety of projects conducted by many people in the two departments. A description of the little victories, the interesting twists, and the roles of persistence, patience, and good luck in this discovery has never been presented in print. Hopefully, this account will serve as an illustration of how scientific advancement can arise from fruitful collaboration and the utilization of many odd bits of information often obtained rather fortuitously. In the early 1950s, Professor Folke Skoog and his group in the Botany Department were continuing their work on the chemical control of new shoot formation in excised pieces of tobacco stems grown in culture (Skoog fondly referred to these de novo formed shoots as “buddies”). This research effort was hindered by the fact that the stem pieces, which were obtained from plants grown in the greenhouse, were difficult to obtain in a sterile and completely healthy condition. The results obtained with the stem segments were quite variable, probably because of the harsh sterilization protocol (mercuric chloride was employed for sterilization), varying light intensities and temperatures at different times of year, as well as greenhouse management procedures. To avoid the difficulties and variability of using greenhouse-grown stem pieces, Skoog sought an alternative tissue to use in these studies. By the 1950s, there had been advances in the art of plant cell culture; in particular, several laboratories had reported that certain complex materials added to an otherwise chemically defined culture medium (consisting of minerals, a carbon source such as Suc, and often the plant hormone auxin) could result in the sustained growth of plant tissues or cells. These materials included coconut (Cocos nucifera) milk, which had first been used by van Overbeek to stimulate the growth of young Datura stramonium embryos in culture (van Overbeek et al., 1941). Skoog explored whether his group could continuously culture tobacco tissue on coconut milk-containing medium, and thereby produce “standardized” samples of tissue for their studies of shoot formation. Skoog's group found that although coconut milk sometimes promoted the proliferation of tobacco tissue, the effect was quite variable; in fact, some batches of coconut milk inhibited growth. They were using coconuts purchased at a local grocery store, and recognized that some of this variability might be due to inhibitors present in certain batches of coconuts. Skoog therefore sought advice from Professor F.C. Steward at Cornell University. Steward's laboratory was attempting to purify and identify materials in coconut milk that promote the growth of carrot (Daucus carota) cells in culture. Skoog hoped to obtain some details of Steward's coconut milk purification procedure, not with the intent to compete with Steward on the identification of the active factor(s) but rather to partially purify the coconut milk factors to an extent that would enable his group to prepare consistently healthy cell cultures for their studies of new shoot formation. Steward replied to this request by sending a letter to Skoog stating that it would be best to leave such matters to the Cornell investigators, and Steward also included a few newspaper clippings that praised his own work but provided no useful details of the purification methods. Skoog, who competed in the 1,500-meter race for Sweden in the 1932 Olympics, was not the type of person who would let such a rebuff go unchallenged. Within minutes of receiving Steward's reply, he contacted Professor Frank Strong, a natural products expert in the Department of Biochemistry at the University of Wisconsin, to initiate a collaboration to compete with Steward's group on the identification of the coconut milk factor(s). The early stages of the project moved rather quickly. Graduate students Jack Mauney (Botany), Rod Clayton (Biochemistry), and Bill Hillman (Botany) did the tough laboratory work of developing methods to purify the active factor(s) and developing a bioassay to test each step of the purification. At first, their assay employed serially cultured tobacco tissue, but later they used callus tissue derived from carrot root pieces. As a starting material for purification of the active factor(s), they shifted to an extract of ground coconut meat rather than the milk because their assays indicated the meat was a richer source of activity. In late 1952, their

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  1. Miller CO (1968) Naturally-occurring cytokinins. In F Wightman, G Setterfield, eds, Biochemistry and Physiology of Plant Growth Substances. Runge Press, Ottawa, pp 33-45

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Authors
Amasino, R.
Affiliations
University of Wisconsin–Madison (US)
Corresponding author
Amasino, Richard
ORCID
Amasino, Richard
Venue
Plant Physiology
Publisher
Oxford University Press (OUP)
Published
2005-07-01
Volume
138
Issue
3
Pages
1177-1184
ISSN
  • 0032-0889 (ISSN-L)
  • 1532-2548
DOI
10.1104/pp.104.900160
PMC
PMC1176392
OpenAlex
W2164804639
Cited by
112
References
25
Citations by year
2026: 2 · 2025: 4 · 2024: 1 · 2023: 18 · 2022: 5 · 2021: 7 · 2020: 17 · 2019: 6 · 2018: 4 · 2017: 8 · 2016: 5 · 2015: 6 · 2014: 5 · 2013: 2 · 2012: 3
FWCI
3.20
Type
journal article
Language
en
Open access
Licence
academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model (vor)
Locations
  • PLANT PHYSIOLOGY (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
Funders
American Cancer Society
Topics
  • Life Sciences › Agricultural and Biological Sciences › Plant Science › Plant Molecular Biology Research
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Plant tissue culture and regeneration
  • Social Sciences › Arts and Humanities › History and Philosophy of Science › History of Science and Medicine
Keywords
kinetin, cytokinins, plant hormones, plant cell culture, shoot organogenesis, coconut milk, plant growth regulators, research collaboration, University of Wisconsin, 50th anniversary
MeSH terms
Adenine, Cell Division, Kinetin, Plant Growth Regulators, Nicotiana, History, 20th Century

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