Editing Arabidopsis thaliana (section)

===Flower development===
{{Further|ABC model of flower development}}
''A. thaliana'' has been extensively studied as a model for flower development. The developing flower has four basic organs - [[sepal]]s, [[petal]]s, [[stamen]]s, and [[Gynoecium|carpel]]s (which go on to form [[Gynoecium|pistil]]s). These organs are arranged in a series of whorls, four sepals on the outer whorl, followed by four petals inside this, six stamens, and a central carpel region. [[Homeotic]] mutations in ''A. thaliana'' result in the change of one organ to another—in the case of the ''agamous'' mutation, for example, stamens become petals and carpels are replaced with a new flower, resulting in a recursively repeated sepal-petal-petal pattern.
[[File:ABC flower development.svg|thumb|150px|The ABC model of flower development was developed through studying ''A. thaliana''.]]

Observations of homeotic mutations led to the formulation of the [[ABC model|ABC model of flower development]] by [[Enrico Coen|E. Coen]] and [[Elliot Meyerowitz|E. Meyerowitz]].<ref>{{cite journal |vauthors=Coen ES, Meyerowitz EM |title=The war of the whorls: genetic interactions controlling flower development |journal=Nature |volume=353 |issue=6339 |pages=31–7 |date=September 1991 |pmid=1715520 |doi=10.1038/353031a0 |bibcode=1991Natur.353...31C |s2cid=4276098}}</ref> According to this model, floral organ identity genes are divided into three classes - class A genes (which affect sepals and petals), class B genes (which affect petals and stamens), and class C genes (which affect stamens and carpels). These genes code for [[transcription factor]]s that combine to cause tissue specification in their respective regions during development. Although developed through study of ''A. thaliana'' flowers, this model is generally applicable to other flowering plants.