Editing Vernalization

{{Short description|Induction of a plant's flowering process}}
{{Use dmy dates|date=May 2021}}
[[File:Hyoscyamus niger Hullukaali Bolmört C IMG 7657.JPG|thumb|Many species of [[henbane]] require vernalization before flowering.]]

'''Vernalization''' ({{etymology|la|{{Wikt-lang|la|vernus}}|of the [[spring (season)|spring]]}}) is the induction of a plant's [[flower]]ing process by exposure to the prolonged cold of [[winter]], or by an artificial equivalent. After vernalization, plants have acquired the ability to flower, but they may require additional seasonal cues or weeks of growth before they will actually do so. The term is sometimes used to refer to the need of herbal (non-woody) plants for a period of cold dormancy in order to produce new shoots and leaves,<ref>{{cite journal |last1=Sokolski |first1=K. |last2=Dovholuk |first2=A. |last3=Dovholuk |first3=L. |last4=Faletra |first4=P. |title=Axenic seed culture and micropropagation of ''Cypripedium reginae'' |journal=Selbyana |volume=18 |issue=2 |year=1997 |pages=172–82 |jstor=41760430 }}</ref> but this usage is discouraged.<ref name = "chouard">{{cite journal
| first1= P. |last1=Chouard|date=June 1960| title = Vernalization and its relations to dormancy| journal = Annual Review of Plant Physiology| volume = 11| pages = 191–238| publisher = Annual Reviews| doi = 10.1146/annurev.pp.11.060160.001203}}</ref>

Many plants grown in [[temperate]] climates require vernalization and must experience a period of low winter temperature to initiate or accelerate the flowering process. This ensures that reproductive development and seed production occurs in spring and winters, rather than in autumn.<ref name = "sung">{{cite journal |last1=Sung |first1=Sibum |last2=He |first2=Yuehui |last3=Eshoo |first3=Tifani W |last4=Tamada |first4=Yosuke |last5=Johnson |first5=Lianna |last6=Nakahigashi |first6=Kenji |last7=Goto |first7=Koji |last8=Jacobsen |first8=Steve E |last9=Amasino |first9=Richard M |title=Epigenetic maintenance of the vernalized state in Arabidopsis thaliana requires LIKE HETEROCHROMATIN PROTEIN 1 |journal=Nature Genetics |volume=38 |issue=6 |pages=706–10 |year=2006 |pmid=16682972 |doi=10.1038/ng1795 |s2cid=2855447 }}</ref> The needed cold is often expressed in [[chilling requirement|chill hours]]. Typical vernalization temperatures are between 1 and 7 degrees Celsius (34 and 45 degrees Fahrenheit).<ref>{{Cite book |last1=Taiz |first1=Lincoln |last2=Murphy |first2=Angus |title=Plant Physiology and Development |date=2015 |publisher=Sinauer Associates |location=Sunderland, Massachusetts (USA) |isbn=978-1-60535-255-8 |page=605}}</ref>

For many [[perennial plants]], such as [[fruit tree]] species, a period of cold is needed first to induce dormancy and then later, after the requisite period, re-emerge from that dormancy prior to flowering. Many [[monocarpic]] [[winter annuals]] and [[biennial plant|biennials]], including some [[ecotype]]s of ''[[Arabidopsis thaliana]]''<ref>{{cite journal |last1=Michaels |first1=Scott D. |last2=He |first2=Yuehui |last3=Scortecci |first3=Katia C. |last4=Amasino |first4=Richard M. |title=Attenuation of FLOWERING LOCUS C activity as a mechanism for the evolution of summer-annual flowering behavior in Arabidopsis |journal=Proceedings of the National Academy of Sciences |volume=100 |issue=17 |pages=10102–7 |year=2003 |pmid=12904584 |pmc=187779 |doi=10.1073/pnas.1531467100 |jstor=3147669 |bibcode=2003PNAS..10010102M |doi-access=free }}</ref> and winter [[cereal]]s such as [[wheat]], must go through a prolonged period of cold before flowering occurs.

==History of vernalization research==
In the [[history of agriculture]], farmers observed a traditional distinction between "winter cereals", whose seeds require chilling (to trigger their subsequent emergence and growth), and "spring cereals", whose seeds can be sown in spring, and germinate, and then flower soon thereafter. Scientists in the early 19th century had discussed how some plants needed cold temperatures to flower. In 1857 an American agriculturist [[John Hancock Klippart]], Secretary of the Ohio Board of Agriculture, reported the importance and effect of winter temperature on the germination of wheat. One of the most significant works was by a German plant physiologist [[Gustav Gassner]] who made a detailed discussion in his 1918 paper. Gassner was the first to systematically differentiate the specific requirements of winter plants from those of summer plants, and also that early swollen germinating seeds of winter cereals are sensitive to cold.<ref>{{cite journal |last1=Chouard |first1=P. |date=1960 |title=Vernalization and its Relations to Dormancy |journal=Annual Review of Plant Physiology |volume=11 |issue=1 |pages=191–238 |doi=10.1146/annurev.pp.11.060160.001203}}</ref>

In 1928, the Soviet agronomist [[Trofim Lysenko]] published his works on the effects of cold on cereal seeds, and coined the term "яровизация" (''yarovizatsiya'' : "jarovization") to describe a chilling process he used to make the seeds of winter cereals behave like spring cereals (from яровой : ''yarvoy'', Tatar root ярый : ''[[Yarilo#Etymology|yaryiy]]'' meaning ardent, fiery, associated with the god of spring). Lysenko himself translated the term into "vernalization" (from the Latin ''vernum'' meaning Spring). After Lysenko the term was used to explain the ability of flowering in some plants after a period of chilling due to physiological changes and external factors. The formal definition was given in 1960 by a French botanist P. Chouard, as "the acquisition or acceleration of the ability to flower by a chilling treatment."<ref>{{cite book |last1=Poltronieri |first1=Palmiro |last2=Hong |first2=Yiguo |title=Applied Plant Genomics and Biotechnology |date=2015 |publisher=Woodhead Publishing |location=Cambridge (UK) |isbn=978-0-08-100068-7 |page=121 |url=https://books.google.com/books?id=tMIcBAAAQBAJ}}</ref>

Lysenko's 1928 paper on vernalization and [[plant physiology]] drew wide attention due to its practical consequences for Russian agriculture. Severe cold and lack of winter snow had destroyed many early winter wheat seedlings. By treating wheat seeds with moisture as well as cold, Lysenko induced them to bear a crop when planted in spring.<ref name="lysenkosci">{{cite journal |last1=Roll-Hansen |first1=Nils |year=1985 |title=A new perspective on Lysenko? |journal=[[Annals of Science]] |publisher=Taylor & Francis |volume=42 |issue=3 |pages=261–278 |doi=10.1080/00033798500200201 |pmid=11620694}}</ref> Later however, according to Richard Amasino, Lysenko inaccurately asserted that the vernalized state could be inherited, i.e. the offspring of a vernalized plant would behave as if they themselves had also been vernalized and would not require vernalization in order to flower quickly.<ref name="amasino">{{cite journal |last1=Amasino |first1=R. |date=2004 |title=Vernalization, Competence, and the Epigenetic Memory of Winter |journal=The Plant Cell |volume=16 |issue=10 |pages=2553–2559 |doi=10.1105/tpc.104.161070 |pmc=520954 |pmid=15466409|bibcode=2004PlanC..16.2553A }}</ref> Opposing this view and supporting Lysenko's claim, Xiuju Li and Yongsheng Liu have detailed experimental evidence from the USSR, Hungary, Bulgaria and China that shows the conversion between spring wheat and winter wheat, positing that "it is not unreasonable to postulate [[Epigenetics|epigenetic mechanisms]] that could plausibly result in the conversion of spring to winter wheat or vice versa."<ref>{{Cite journal|last1=Li|first1=Xiuju|last2=Liu|first2=Yongsheng|date=2010-05-06|title=The conversion of spring wheat into winter wheat and vice versa: false claim or Lamarckian inheritance?|url=http://link.springer.com/10.1007/s12038-010-0035-1|journal=Journal of Biosciences|language=en|volume=35|issue=2|pages=321–325|doi=10.1007/s12038-010-0035-1|pmid=20689187|s2cid=10527354|issn=0250-5991|url-access=subscription}}</ref>

Early research on vernalization focused on plant physiology; the increasing availability of molecular biology has made it possible to unravel its underlying mechanisms.<ref name="amasino"/> For example, a lengthening daylight period (longer days), ''as well as'' cold temperatures are required for winter wheat plants to go from the vegetative to the reproductive state; the three interacting genes are called ''VRN1'', ''VRN2'', and ''FT'' (''VRN3'').<ref name="trevaskis">{{cite journal | first1= Ben |last1=Trevaskis |first2=Megan N. |last2=Hemming |first3=Elizabeth S. |last3=Dennis |date=August 2007 | title=The molecular basis of vernalization-induced flowering in cereals | journal=Trends in Plant Science | volume=12 | pmid=17629542 | issue=8 | pages=352–357 | publisher=Elsevier | doi=10.1016/j.tplants.2007.06.010|bibcode=2007TPS....12..352T }}</ref>

==In ''Arabidopsis thaliana''==
[[File:Arabidopsis thaliana rosette.png|thumb|''[[Arabidopsis thaliana]]'' rosette before vernalization, with no floral spike]]
''[[Arabidopsis thaliana]]'' ("thale cress") is a much-studied model for vernalization. Some ecotypes (varieties), called "winter annuals", have delayed flowering without vernalization; others ("summer annuals") do not.<ref name ="pbvr">{{cite web |url= http://www.plant-biology.com/vernalisation-response.php
      |title= Vernalisation response
      |access-date=2011-01-26
      |publisher= Plant Biology }}{{self-published source|date=March 2016}}</ref>{{self-published inline|date=March 2016}} The genes that underlie this difference in plant physiology have been intensively studied.<ref name = "amasino"/>

The reproductive phase change of ''A. thaliana'' occurs by a sequence of two related events: first, the [[Bolting (horticulture)|bolting]] transition (flower stalk elongates), then the floral transition (first flower appears).<ref name=pouteau>{{cite journal |last1=Pouteau |first1=Sylvie |last2=Albertini |first2=Catherine |title=The significance of bolting and floral transitions as indicators of reproductive phase change in ''Arabidopsis'' |journal=Journal of Experimental Botany |volume=60 |issue=12 |pages=3367–77 |year=2009 |pmid=19502535 |doi=10.1093/jxb/erp173 |doi-access=free }}</ref> Bolting is a robust predictor of flower formation, and hence a good indicator for vernalization research.<ref name = "pouteau"/>

In winter annual ''Arabidopsis'', vernalization of the [[meristem]] appears to confer competence to respond to floral inductive signals. A vernalized meristem retains competence for as long as 300 days in the absence of an inductive signal.<ref name ="pbvr"/>

At the molecular level, flowering is repressed by the protein ''Flowering Locus C'' (''FLC''), which binds to and represses genes that promote flowering, thus blocking flowering.<ref name = "sung"/><ref>{{cite journal |last1=Amasino |first1=Richard |title=Seasonal and developmental timing of flowering |journal=The Plant Journal |volume=61 |issue=6 |pages=1001–13 |year=2010 |pmid=20409274 |doi=10.1111/j.1365-313X.2010.04148.x |doi-access=free }}</ref> Winter annual ecotypes of Arabidopsis have an active copy of the gene ''FRIGIDA'' (''FRI''), which promotes ''FLC'' expression, thus repression of flowering.<ref>{{cite journal |last1=Choi |first1=Kyuha |last2=Kim |first2=Juhyun |last3=Hwang |first3=Hyun-Ju |last4=Kim |first4=Sanghee |last5=Park |first5=Chulmin |last6=Kim |first6=Sang Yeol |last7=Lee |first7=Ilha |title=The FRIGIDA Complex Activates Transcription ofFLC, a Strong Flowering Repressor in Arabidopsis, by Recruiting Chromatin Modification Factors |journal=The Plant Cell |volume=23 |issue=1 |pages=289–303 |year=2011 |pmid=21282526 |pmc=3051252 |doi=10.1105/tpc.110.075911 |bibcode=2011PlanC..23..289C }}</ref> Prolonged exposure to cold (vernalization) induces expression of ''VERNALIZATION INSENSTIVE3'', which interacts with the ''VERNALIZATION2'' (''VRN2'') polycomb-like complex to reduce ''FLC'' expression through chromatin remodeling.<ref name = "Sung and Amasino">{{cite journal
| last1 = Sung
| first1 = Sibum
| last2 = Amasino
| first2 =Richard M.
| year = 2004
| title = Vernalization in Arabidopsis thaliana is mediated by the PHD finger protein VIN3
| journal = Nature
| volume = 427
| pages = 159–163
| bibcode = 2004Natur.427..159S
| doi = 10.1038/nature02195
| pmid = 14712276
| issue = 6970
| s2cid = 4418494
}}</ref> Levels of VRN2 protein increase during long-term cold exposure as a result of inhibition of VRN2 turnover via its N-degron.<ref>{{cite journal |last1=Gibbs |first1=DJ |last2=Tedds |first2=HM |last3=Labandera |first3=AM |last4=Bailey |first4=M |last5=White |first5=MD |last6=Hartman |first6=S |last7=Sprigg |first7=C |last8=Mogg |first8=SL |last9=Osborne |first9=R |last10=Dambire |first10=C |last11=Boeckx |first11=T |last12=Paling |first12=Z |last13=Voesenek |first13=LACJ |last14=Flashman |first14=E |last15=Holdsworth |first15=MJ |title=Oxygen-dependent proteolysis regulates the stability of angiosperm polycomb repressive complex 2 subunit VERNALIZATION 2. |journal=Nature Communications |date=21 December 2018 |volume=9 |issue=1 |pages=5438 |doi=10.1038/s41467-018-07875-7 |pmid=30575749|pmc=6303374 |bibcode=2018NatCo...9.5438G}}</ref><ref>{{cite journal |last1=Osborne |first1=Rory |last2=Labandera |first2=Anne-Marie |last3=Ryder |first3=Alex J. |last4=Kanali |first4=Anastasia |last5=Xu |first5=Tianyuan |last6=Akintewe |first6=Oluwatunmise |last7=Schwarze |first7=Maximillian A. |last8=Morgan |first8=Christian D. |last9=Hartman |first9=Sjon |last10=Kaiserli |first10=Eirini |last11=Gibbs |first11=Daniel J. |title=VRN2-PRC2 facilitates light-triggered repression of PIF signaling to coordinate growth in Arabidopsis |journal=Developmental Cell |date=26 March 2025 |doi=10.1016/j.devcel.2025.03.001 |pmid=40147448 |doi-access=free }}</ref> The events of histone deacetylation at Lysine 9 and 14 followed by methylation at Lys 9 and 27 is associated with the vernalization response. The epigenetic silencing of ''FLC'' by chromatin remodeling is also thought to involve the cold-induced expression of antisense ''FLC COOLAIR''<ref>http://www.jic.ac.uk/news/2014/10/plants-require-coolair-flower-spring {{Webarchive|url=https://web.archive.org/web/20150423163727/https://www.jic.ac.uk/news/2014/10/plants-require-coolair-flower-spring/ |date=23 April 2015 }}{{full citation needed|date=March 2016}}</ref><ref name = "Csorba">{{cite journal |last1=Csorba |first1=Tibor |last2=Questa |first2=Julia I. |last3=Sun |first3=Qianwen |last4=Dean |first4=Caroline |title=Antisense COOLAIR mediates the coordinated switching of chromatin states atFLCduring vernalization |journal=Proceedings of the National Academy of Sciences |volume=111 |issue=45 |pages=16160–5 |year=2014 |pmid=25349421 |pmc=4234544 |doi=10.1073/pnas.1419030111 |bibcode=2014PNAS..11116160C |doi-access=free }}</ref> or ''COLDAIR'' transcripts.<ref name=pmid21127216>{{cite journal |last1=Heo |first1=J. B. |last2=Sung |first2=S. |title=Vernalization-Mediated Epigenetic Silencing by a Long Intronic Noncoding RNA |journal=Science |volume=331 |issue=6013 |pages=76–9 |year=2011 |pmid=21127216 |doi=10.1126/science.1197349 |bibcode=2011Sci...331...76H |s2cid=19127414 }}</ref> Vernalization is registered by the plant by the stable silencing of individual ''FLC'' [[locus (genetics)|loci]].<ref name = "Angel">{{cite journal |last1=Angel |first1=Andrew |last2=Song |first2=Jie |last3=Dean |first3=Caroline |last4=Howard |first4=Martin |title=A Polycomb-based switch underlying quantitative epigenetic memory |journal=Nature |volume=476 |issue=7358 |pages=105–8 |year=2011 |pmid=21785438 |doi=10.1038/nature10241 |s2cid=205225603 }}</ref> The removal of silent chromatin marks at ''FLC'' during embryogenesis prevents the inheritance of the vernalized state.<ref name = "Crevillen">{{cite journal |last1=Crevillén |first1=Pedro |last2=Yang |first2=Hongchun |last3=Cui |first3=Xia |last4=Greeff |first4=Christiaan |last5=Trick |first5=Martin |last6=Qiu |first6=Qi |last7=Cao |first7=Xiaofeng |last8=Dean |first8=Caroline |title=Epigenetic reprogramming that prevents trans-generational inheritance of the vernalized state |journal=Nature |volume=515 |issue=7528 |pages=587–90 |year=2014 |pmid=25219852 |pmc=4247276 |doi=10.1038/nature13722 |bibcode=2014Natur.515..587C }}</ref>

Since vernalization also occurs in ''flc'' mutants (lacking ''FLC''), vernalization must also activate a non-''FLC'' pathway.<ref name ="pbvp">{{cite web |url= http://www.plant-biology.com/vernalisation-pathway-Arabidopsis.php
      |title= Vernalisation pathway
      |access-date=2011-01-26
      |publisher= Plant Biology }}{{self-published source|date=March 2016}}</ref>{{self-published inline|date=March 2016}} A day-length mechanism is also important.<ref name = "trevaskis"/> Vernalization response works in concert with the photo-periodic genes CO, FT, PHYA, CRY2 to induce flowering.

==Devernalization==
It is possible to devernalize a plant by
exposure to sometimes low and high temperatures subsequent to vernalization. For example, commercial [[onion]] growers store sets at low temperatures, but devernalize them before planting, because they want the plant's energy to go into enlarging its bulb (underground stem), not making flowers.<ref>
  {{
     cite encyclopedia
       | encyclopedia = Encyclopædia Britannica Online
       | title = Vernalization
|url= https://www.britannica.com/topic/vernalization
       | quote = Devernalization can be brought about by high temperatures ... Onion sets ... are ... ready to flower ... temperatures above 26.7&nbsp;°C (80&nbsp;°F) ..., however, shifts the sets to the desired bulb-forming phase.
       | access-date = 2023-09-03
  }}
</ref>

== See also ==
* [[Stratification (seeds)]]

== References ==
{{reflist}}

== External links ==
* [https://www.newscientist.com/channel/earth/mg19526152.400-the-word-vernalisation.html Article in New Scientist]

{{Lysenkoism}}

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[[Category:Agricultural terminology]]
[[Category:Plant physiology]]
[[Category:Winter phenomena]]