Editing Nod factor (section)

== Chemical Structure ==
Nod factors structurally are lipochitooligosaccharides (LCOs) that consist of an [[N-Acetylglucosamine|''N''-acetyl-<small>D</small>-glucosamine]] chain linked through β-1,4 linkage with a fatty acid of variable identity attached to a non reducing nitrogen in the backbone with various [[functional group]] substitutions at the terminal or non-terminal residues.<ref>{{cite journal | author = Spaink HP. | year = 1992 | title = Rhizobial lipo-oligosaccharides: Answers and questions | journal = Plant Molecular Biology | volume = 20 | issue = 5 | pages = 977–986 | doi = 10.1007/BF00027167 | pmid = 1463833 | bibcode = 1992PMolB..20..977S | s2cid = 30609937 | issn = 1573-5028| hdl = 1887/3736313 | hdl-access = free }}</ref>

Nod factors are produced in complex mixtures differing in the following characteristics:<ref>{{cite journal | author = Spaink HP | year = 2000 | title = Root nodulation and infection factors produced by rhizobial bacteria | journal = Annual Review of Microbiology | volume = 54 | issue = 1 | pages = 257–288| doi = 10.1146/annurev.micro.54.1.257 | pmid = 11018130 | hdl = 1887/3748257 | hdl-access = free }}</ref>

* Length of the chain can vary from three to six units of ''N''-acetyl-<small>D</small>-glucosamine with the exception of ''M. loti'' which can produce Nod factors with two unit only.
* Presence or absence of strain-specific substitutions along the chain
* Identity of the fatty acid component
* Presence or absence of unsaturated fatty acids

Nod gene expression is induced by the presence of certain [[flavonoid]]s in the soil, which are secreted by the plant and act as an attractant to bacteria and induce Nod factor production. Flavonoids activate NodD, a LysR family transcription factor, which binds to the ''nod'' box and initiates the transcription of the nod genes which encode the proteins necessary for the production of a wide range of LCOs.<ref>{{cite journal |vauthors=Zuanazzi JA, Clergeot PH, Quirion JC, Husson HP, Kondorosi Á, Ratet P | year = 1998 | title = Production of ''Sinorhizobium meliloti nod'' gene activator and repressor flavonoids from ''Medicago sativa'' roots | journal = Molecular Plant-Microbe Interactions | volume = 11 | issue = 8 | pages = 784–794| doi = 10.1094/MPMI.1998.11.8.784 | doi-access = free | bibcode = 1998MPMI...11..784Z }}</ref>