Editing Vernalization (section)

==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.