Editing Botany (section)

=== Molecular genetics ===
{{Further|Molecular genetics}}
[[File:Arabidopsis thaliana inflorescencias.jpg|thumb|alt=Flowers of Arabidopsis thaliana, the most important model plant and the first to have its genome sequenced|Thale cress, ''[[Arabidopsis thaliana]]'', the first plant to have its genome sequenced, remains the most important model organism.]]
A considerable amount of new knowledge about plant function comes from studies of the molecular genetics of [[model organism#Plants|model plants]] such as the Thale cress, ''[[Arabidopsis thaliana]]'', a weedy species in the mustard family ([[Brassicaceae]]).{{sfn|Benderoth|Textor|Windsor|Mitchell-Olds|2006|pp = 9118–9123}} The [[genome]] or hereditary information contained in the genes of this species is encoded by about 135 million [[base pairs]] of DNA, forming one of the smallest genomes among [[flowering plant]]s. ''Arabidopsis'' was the first plant to have its genome sequenced, in 2000.{{sfn|Arabidopsis Genome Initiative|2000|pp = 796–815}} The sequencing of some other relatively small genomes, of rice (''[[Oryza sativa]]''){{sfn|Devos|Gale|2000}} and ''[[Brachypodium distachyon]]'',{{sfn|University of California-Davis|2012}} has made them important model species for understanding the genetics, cellular and molecular biology of [[cereals]], [[grasses]] and [[monocots]] generally.

[[Model organism#Plants|Model plants]] such as ''Arabidopsis thaliana'' are used for studying the molecular biology of [[plant cell]]s and the [[chloroplast]]. Ideally, these organisms have small genomes that are well known or completely sequenced, small stature and short generation times. Corn has been used to study mechanisms of [[photosynthesis]] and [[phloem]] loading of sugar in [[C4 plants|{{C4}} plants]].{{sfn|Russin|Evert|Vanderveer|Sharkey|1996|pp = 645–658}} The [[single celled]] [[green alga]] ''[[Chlamydomonas reinhardtii]]'', while not an [[embryophyte]] itself, contains a [[chlorophyll b|green-pigmented]] [[Chloroplast#Chloroplastida (green algae and plants)|chloroplast]] related to that of land plants, making it useful for study.{{sfn|Rochaix|Goldschmidt-Clermont|Merchant|1998|p = 550}} A [[red alga]] ''[[Cyanidioschyzon merolae]]'' has also been used to study some basic chloroplast functions.{{sfn|Glynn|Miyagishima|Yoder|Osteryoung|2007|pages = 451–461}} [[Spinach]],{{sfn|Possingham|Rose|1976|pp = 295–305}} [[peas]],{{sfn|Sun|Forouhar|Li Hm|Tu|2002|pp = 95–100}} [[soybeans]] and a moss ''[[Physcomitrella patens]]'' are commonly used to study plant cell biology.{{sfn|Heinhorst|Cannon|1993|pp = 1–9}}

''[[Agrobacterium tumefaciens]]'', a soil [[rhizosphere]] bacterium, can attach to plant cells and infect them with a [[Callus (cell biology)|callus]]-inducing [[Ti plasmid]] by [[horizontal gene transfer]], causing a callus infection called crown gall disease. Schell and Van Montagu (1977) hypothesised that the Ti plasmid could be a natural vector for introducing the [[Nif gene]] responsible for [[nitrogen fixation]] in the root nodules of [[Fabaceae|legumes]] and other plant species.{{sfn|Schell|Van Montagu|1977|pp = 159–179}} Today, genetic modification of the Ti plasmid is one of the main techniques for introduction of [[transgene]]s to plants and the creation of [[genetically modified crops]].