I. How Plants “Know” When to Flower
II. Vernalization: How Winter Cold Promotes Flowering
Part I: How Plants “Know” When to Flower
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Plants flower in response to changes in environmental cues such as day length (photoperiodism) and temperature. Amasino explains that Arabidopsis thaliana, a common model plant, typically flowers in response to long days. There are, however, a number of mutants that either flower when days are short or don’t flower when days are long. These mutants have allowed scientists to identify a key regulator of flowering called CONSTANS. When CONSTANS is expressed in the presence of light, it triggers a cascade of protein expression and migration that ultimately results in flower formation.
In his second talk, Amasino explains that some plants germinate and begin growing in the fall but do not flower and produce seeds until spring. For these plants, a long period of cold weather (vernalization) is necessary to induce flowering. This ensures that the plant does not accidentally flower during the winter. Using Arabidopsis mutants, Amasino and his colleagues found another key protein regulator of flowering (FLC). Expression of FLC represses the photoperiodism pathway and prevents flowering. Vernalization inhibits the expression of FLC, thus removing the repression and allowing the plants to flower. Amasino also found that Arabidopis thaliana has a “memory” of winter due to modification of FLC chromatin.
Rick Amasino is a Distinguished Professor of Biochemistry at the University of Wisconsin-Madison and a Howard Hughes Medical Institute Professor. His lab uses genetics and biochemistry to study plant development and the regulation of flowering. Amasino also encourages undergraduate students to explore genetics through experiments with Brassica rapa.
Amasino has been honored with numerous awards for both teaching and research. He is a Fellow of the American Association for the Advancement of Science and was elected to the National Academy of Sciences in 2006.
Amasino received his BS in biology from Pennsylvania State University and his PhD in biology and biochemistry from Indiana University, Bloomington.
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Lee J, Yun JY, Zhao W, Shen WH, Amasino RM. A methyltransferase required for proper timing of the vernalization response in Arabidopsis.
Proc Natl Acad Sci U S A. 2015 Feb 17;112(7):2269-74. PMID: 25605879
Amasino RM. My favourite flowering image: Maryland Mammoth tobacco. J Exp Bot. 2013 Dec;64(18):5817-8. PMID: 23633243
Ream TS, Woods DP, Amasino RM. The molecular basis of vernalization in different plant groups. Cold Spring Harb Symp Quant Biol. 2012;77:105-15. Review. PMID: 23619014
Amasino RM, Michaels SD. The timing of flowering. Plant Physiol. 2010 Oct;154(2):516-20. PMID: 20921176
Ko JH, Mitina I, Tamada Y, Hyun Y, Choi Y, Amasino RM, Noh B, Noh YS. Growth habit determination by the balance of histone methylation activities in Arabidopsis. EMBO J. 2010 Sep 15;29(18):3208-15. PMID: 20711170
Amasino R. Seasonal and developmental timing of flowering. Plant J. 2010 Mar;61(6):1001-13. Review. PMID: 20409274
Schmitz RJ, Sung S, Amasino RM. Histone arginine methylation is required for vernalization-induced epigenetic silencing of FLC in winter-annual Arabidopsis thaliana. Proc Natl Acad Sci U S A. 2008 Jan 15;105(2):411-6. PMID: 18178621
Kim SY, He Y, Jacob Y, Noh YS, Michaels S, Amasino R. Establishment of the vernalization-responsive, winter-annual habit in Arabidopsis requires a putative histone H3 methyl transferase. Plant Cell. 2005 Dec;17(12):3301-10. PMID: 16258034
Doyle MR, Davis SJ, Bastow RM, McWatters HG, Kozma-Bognár L, Nagy F, Millar AJ, Amasino RM. The ELF4 gene controls circadian rhythms and flowering time in Arabidopsis thaliana. Nature. 2002 Sep 5;419(6902):74-7. PMID: 12214234