Editing Gibberellin (section)

==Chemistry==
All known gibberellins are [[Diterpene#Diterpenoids|diterpenoid]] acids synthesized by the terpenoid pathway in [[plastid]]s and then modified in the [[endoplasmic reticulum]] and [[cytosol]] until they reach their biologically active form.<ref name="Campbell-2002">{{cite book | vauthors = Campbell N, Reec JB | author-link1 = Neil Campbell (scientist) | title = Biology | url = https://archive.org/details/biologyc00camp | url-access = registration | edition = 6th | location = San Francisco | publisher = Benjamin Cummings | year = 2002 | isbn = 9780805366242 }}</ref> All are derived via the ''ent''-gibberellane skeleton but are synthesised via ''ent''-kaurene. The gibberellins are named GA<sub>1</sub> through GA<sub>n</sub> in order of discovery.<ref name="Sponsel-2010">{{Citation|last1=Sponsel|first1=Valerie M.|title=Gibberellin Biosynthesis and Inactivation|date=2010|url=http://link.springer.com/10.1007/978-1-4020-2686-7_4|work=Plant Hormones|pages=63–94|editor-last=Davies|editor-first=Peter J.|place=Dordrecht|publisher=Springer Netherlands|language=en|doi=10.1007/978-1-4020-2686-7_4|isbn=978-1-4020-2684-3|access-date=2022-01-29|last2=Hedden|first2=Peter|url-access=subscription}}</ref> [[Gibberellic acid]], which was the first gibberellin to be structurally characterized, is GA<sub>3</sub>.<ref name="Hedden-2020">{{Cite journal|last=Hedden|first=Peter|date=2020-11-23|title=The Current Status of Research on Gibberellin Biosynthesis|url=https://doi.org/10.1093/pcp/pcaa092|journal=Plant and Cell Physiology|volume=61|issue=11|pages=1832–1849|doi=10.1093/pcp/pcaa092|issn=1471-9053|pmc=7758035|pmid=32652020}}</ref>

{{As of|2020}},<ref name="Sponsel-2010" /> there are 136 GAs identified from plants, fungi, and bacteria.<ref name="Hedden-2015" /><ref name="Hedden-2020" /><ref name="Sponsel-2010" />

Gibberellins are tetracyclic diterpene acids. There are two classes, with either 19 or 20 carbons. The 19-carbon gibberellins are generally the biologically active forms. They have lost carbon 20 and, in place, possess a five-member [[lactone]] bridge that links carbons 4 and 10. [[Hydroxylation]] also has a great effect on its biological activity. In general, the most biologically active compounds are dihydroxylated gibberellins, with hydroxyl groups on both carbons 3 and 13. Gibberellic acid is a 19-carbon dihydroxylated gibberellin.<ref name="AccessScience">{{cite journal | doi = 10.1036/1097-8542.289000 | title=Gibberellins | journal=AccessScience}}</ref>

===Bioactive GAs===
The bioactive Gibberellins are GA<sub>1</sub>, GA<sub>3</sub>, GA<sub>4</sub>, and GA<sub>7</sub>.<ref name="Yamaguchi-2008">{{cite journal | vauthors = Yamaguchi S | title = Gibberellin metabolism and its regulation | journal = Annual Review of Plant Biology | volume = 59 | pages = 225–51 | year = 2008 | pmid = 18173378 | doi = 10.1146/annurev.arplant.59.032607.092804 }}</ref> There are three common structural traits between these GAs: 1) hydroxyl group on C-3β, 2) a carboxyl group on carbon 6, and 3) a lactone between carbons 4 and 10.<ref name="Yamaguchi-2008" /> 

<gallery perrow="4">
File:Gibberellin A1 v2.svg|{{center|Gibberellin A<sub>1</sub> (GA<sub>1</sub>)}}
File:Gibberellic acid.svg|{{center|[[Gibberellic acid]] (GA<sub>3</sub>)}}
File:Ent-Gibberellane.svg|{{center|''ent''-Gibberellane}}
File:Ent-Kauren.svg|{{center|''ent''-Kaurene}}
</gallery>

The 3β-hydroxyl group can be exchanged for other functional groups at C-2 and/or C-3 positions.<ref name="Yamaguchi-2008" /> GA<sub>5</sub> and GA<sub>6</sub> are examples of bioactive GAs without a hydroxyl group on C-3β.<ref name="Yamaguchi-2008" /> The presence of GA<sub>1</sub> in various plant species suggests that it is a common bioactive GA.<ref>{{cite journal | vauthors = MacMillan J | title = Occurrence of Gibberellins in Vascular Plants, Fungi, and Bacteria | journal = Journal of Plant Growth Regulation | volume = 20 | issue = 4 | pages = 387–442 | date = December 2001 | pmid = 11986764 | doi = 10.1007/s003440010038 | s2cid = 44504525 }}</ref>