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<title>Nod factor</title>

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<span id="openzim-page-title" class="mw-page-title-main"><span class="mw-page-title-main">Nod factor</span></span>

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<p><b>Nod factors</b> (<b>nodulation factors</b> or <b>NF</b>), are <a href="Signaling_molecule" class="mw-redirect" title="Signaling molecule">signaling molecules</a> produced by <a href="Soil_microbiology" title="Soil microbiology">soil bacteria</a> known as <a href="Rhizobia" title="Rhizobia">rhizobia</a> in response to flavonoid exudation from plants under nitrogen limited conditions. Nod factors initiate the establishment of a symbiotic relationship between legumes and rhizobia by inducing <a href="Root_nodule" title="Root nodule">nodulation.</a> Nod factors produce the differentiation of plant tissue in root hairs into nodules where the bacteria reside and are able to <a href="Nitrogen_fixation" title="Nitrogen fixation">fix nitrogen</a> from the atmosphere for the plant in exchange for photosynthates and the appropriate environment for nitrogen fixation.<sup id="cite_ref-1" class="reference"><a href="#cite_note-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup> One of the most important features provided by the plant in this symbiosis is the production of <a href="Leghemoglobin" title="Leghemoglobin">leghemoglobin</a>, which maintains the oxygen concentration low and prevents the inhibition of <a href="Nitrogenase" title="Nitrogenase">nitrogenase</a> activity.

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<div class="mw-heading mw-heading2"><h2 id="Chemical_Structure">Chemical Structure</h2></div>

<p>Nod factors structurally are lipochitooligosaccharides (LCOs) that consist of an <a href="N-Acetylglucosamine" title="N-Acetylglucosamine"><i>N</i>-acetyl-<small>D</small>-glucosamine</a> 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 <a href="Functional_group" title="Functional group">functional group</a> substitutions at the terminal or non-terminal residues.<sup id="cite_ref-2" class="reference"><a href="#cite_note-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup>

</p><p>Nod factors are produced in complex mixtures differing in the following characteristics:<sup id="cite_ref-3" class="reference"><a href="#cite_note-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup>

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<ul><li>Length of the chain can vary from three to six units of <i>N</i>-acetyl-<small>D</small>-glucosamine with the exception of <i>M. loti</i> which can produce Nod factors with two unit only.</li>

<li>Presence or absence of strain-specific substitutions along the chain</li>

<li>Identity of the fatty acid component</li>

<li>Presence or absence of unsaturated fatty acids</li></ul>

<p>Nod gene expression is induced by the presence of certain <a href="Flavonoid" title="Flavonoid">flavonoids</a> 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 <i>nod</i> box and initiates the transcription of the nod genes which encode the proteins necessary for the production of a wide range of LCOs.<sup id="cite_ref-4" class="reference"><a href="#cite_note-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Function">Function</h2></div>

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</style><div role="note" class="hatnote navigation-not-searchable">See also: <a href="Common_Symbiotic_Signaling_Pathway" class="mw-redirect" title="Common Symbiotic Signaling Pathway">Common Symbiotic Signaling Pathway</a></div>

<p>Nod factors are potentially recognized by plant receptors made of two <a href="Histidine_kinase" title="Histidine kinase">histidine kinases</a> with extracellular <a href="LysM_domain" title="LysM domain">LysM domain</a>, which have been identified in <i><a href="Lotus_japonicus" title="Lotus japonicus">L. japonicus</a>,</i> <a href="Soybean" title="Soybean">soybean</a>, and <i><a href="Medicago_truncatula" title="Medicago truncatula">M. truncatula</a></i> <sup id="cite_ref-:0_5-0" class="reference"><a href="#cite_note-:0-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup><i>.</i> Binding of Nod factors to these receptors depolarizes the plasma membrane of root hairs via an influx of Ca<sup>+2</sup> which induce the expression of early nodulin (ENOD) genes and swelling of the root hairs. In M. truncatula, the signal transduction initiates by the activation of <i>dmi1, dmi2</i>, and <i>dmi3</i> which lead to the deformation of root hairs, early nodulin expression, cortical cell division and bacterial infection. Additionally, <i>nsp</i> and <i>hcl</i> genes are recruited later and aid in the process of early nodulation expression, cortical cell division, and infection.<sup id="cite_ref-6" class="reference"><a href="#cite_note-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> Genes <i>dmi1, dmi2, and dmi3</i> have also been found to aid in the establishment of interactions between <i>M. truncatula</i> and <a href="Arbuscular_mycorrhiza" title="Arbuscular mycorrhiza">arbuscular mycorrhiza</a>, indicating that the two very different symbioses may share some common mechanisms.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> The end result is the nodule, the structure in which nitrogen is fixed. Nod factors act by inducing changes in gene expression in the legume, most notable the nodulin genes, which are needed for nodule organogenesis.<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Nodulation">Nodulation</h2></div>

<p>Rhizobia bind to host specific lectins present in root hairs which together with Nod factors lead to the formation of nodulation. Nod factors are recognized by a specific class of <a href="Receptor_(biochemistry)" title="Receptor (biochemistry)">receptor</a> <a href="Kinase" title="Kinase">kinases</a> that have <a href="LysM_domain" title="LysM domain">LysM domains</a> in their extracellular domains. The two LysM (lysin motif) receptor kinases (NFR1 and NFR5) that appear to make up the Nod factor receptor were first isolated in the <a href="Model_organism" title="Model organism">model</a> legume <i><a href="Lotus_japonicus" title="Lotus japonicus">Lotus japonicus</a></i> in 2003. They now have been isolated also from <a href="Soybean" title="Soybean">soybean</a> and the model legume <i><a href="Medicago_truncatula" title="Medicago truncatula">Medicago truncatula</a></i>. NFR5 lacks the classical <a href="Activation_loop" class="mw-redirect" title="Activation loop">activation loop</a> in the <a href="Kinase" title="Kinase">kinase</a> domain. The <i>NFR5</i> gene lacks <a href="Intron" title="Intron">introns</a>. First the cell membrane is depolarized and the root hairs start to swell and cell division stops. Nod factor cause the fragmentation and rearrangement of actin network, which coupled with the reinstitution of cell growth lead to the <a href="Root_hair_curling" class="mw-redirect" title="Root hair curling">curling of the root hair</a> around the bacteria. This is followed by the localized breakdown of the cell wall and the invagination of the plant cell membrane, allowing the bacterium to form an infection thread. As the infection thread grows the rhizobia travel down its length towards the site of the nodule. During this process the pericycle cells in plants become activated and cells in the inner cortex start growing and become the nodule primordium where the rhizobia infect and differentiate into bacteroids and fix nitrogen. Activation of adjacent middle cortex cells leads to the formation of nodule meristem.<sup id="cite_ref-:0_5-1" class="reference"><a href="#cite_note-:0-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup>

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<div class="mw-heading mw-heading2"><h2 id="Notes">Notes</h2></div>

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<li id="cite_note-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-1">^</a></b></span> <span class="reference-text"><i>Stambulska, U.Y. and Bayliak, M.M., 2020. Legume-Rhizobium Symbiosis: Secondary Metabolites, Free Radical Processes, and Effects of Heavy Metals. Co-Evolution of Secondary Metabolites, pp.291-322.</i></span>

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</style><cite id="CITEREFSpaink_HP.1992" class="citation journal cs1">Spaink HP. (1992). "Rhizobial lipo-oligosaccharides: Answers and questions". <i>Plant Molecular Biology</i>. <b>20</b> (5): <span class="nowrap">977–</span>986. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1992PMolB..20..977S">1992PMolB..20..977S</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1007%2FBF00027167">10.1007/BF00027167</a>. <a href="Hdl_(identifier)" class="mw-redirect" title="Hdl (identifier)">hdl</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://hdl.handle.net/1887%2F3736313">1887/3736313</a></span>. <a href="ISSN_(identifier)" class="mw-redirect" title="ISSN (identifier)">ISSN</a> <a rel="nofollow" class="external text" href="https://search.worldcat.org/issn/1573-5028">1573-5028</a>. <a href="PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/1463833">1463833</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:30609937">30609937</a>.</cite></span>

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<li id="cite_note-3"><span class="mw-cite-backlink"><b><a href="#cite_ref-3">^</a></b></span> <span class="reference-text"><cite id="CITEREFSpaink_HP2000" class="citation journal cs1">Spaink HP (2000). "Root nodulation and infection factors produced by rhizobial bacteria". <i>Annual Review of Microbiology</i>. <b>54</b> (1): <span class="nowrap">257–</span>288. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1146%2Fannurev.micro.54.1.257">10.1146/annurev.micro.54.1.257</a>. <a href="Hdl_(identifier)" class="mw-redirect" title="Hdl (identifier)">hdl</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://hdl.handle.net/1887%2F3748257">1887/3748257</a></span>. <a href="PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/11018130">11018130</a>.</cite></span>

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<li id="cite_note-4"><span class="mw-cite-backlink"><b><a href="#cite_ref-4">^</a></b></span> <span class="reference-text"><cite id="CITEREFZuanazziClergeotQuirionHusson1998" class="citation journal cs1">Zuanazzi JA, Clergeot PH, Quirion JC, Husson HP, Kondorosi Á, Ratet P (1998). <a rel="nofollow" class="external text" href="https://doi.org/10.1094%2FMPMI.1998.11.8.784">"Production of <i>Sinorhizobium meliloti nod</i> gene activator and repressor flavonoids from <i>Medicago sativa</i> roots"</a>. <i>Molecular Plant-Microbe Interactions</i>. <b>11</b> (8): <span class="nowrap">784–</span>794. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1998MPMI...11..784Z">1998MPMI...11..784Z</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1094%2FMPMI.1998.11.8.784">10.1094/MPMI.1998.11.8.784</a></span>.</cite></span>

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<li id="cite_note-:0-5"><span class="mw-cite-backlink">^ <a href="#cite_ref-:0_5-0"><sup><i><b>a</b></i></sup></a> <a href="#cite_ref-:0_5-1"><sup><i><b>b</b></i></sup></a></span> <span class="reference-text"><cite id="CITEREFGage2004" class="citation journal cs1">Gage DJ (June 2004). <a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC419923">"Infection and invasion of roots by symbiotic, nitrogen-fixing rhizobia during nodulation of temperate legumes"</a>. <i>Microbiology and Molecular Biology Reviews</i>. <b>68</b> (2): <span class="nowrap">280–</span>300. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1128%2FMMBR.68.2.280-300.2004">10.1128/MMBR.68.2.280-300.2004</a>. <a href="PMC_(identifier)" class="mw-redirect" title="PMC (identifier)">PMC</a> <span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC419923">419923</a></span>. <a href="PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/15187185">15187185</a>.</cite></span>

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<li id="cite_note-6"><span class="mw-cite-backlink"><b><a href="#cite_ref-6">^</a></b></span> <span class="reference-text"><cite id="CITEREFOldroyd2001" class="citation journal cs1">Oldroyd, G (2001). <a rel="nofollow" class="external text" href="https://doi.org/10.1006%2Fanbo.2001.1410">"Dissecting Symbiosis: Developments in Nod Factor Signal Transduction"</a>. <i>Annals of Botany</i>. <b>87</b> (6): <span class="nowrap">709–</span>718. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/2001AnBot..87..709O">2001AnBot..87..709O</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1006%2Fanbo.2001.1410">10.1006/anbo.2001.1410</a></span>.</cite></span>

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<li id="cite_note-7"><span class="mw-cite-backlink"><b><a href="#cite_ref-7">^</a></b></span> <span class="reference-text"><cite id="CITEREFOláhBrièreBécardDénarié2005" class="citation journal cs1">Oláh B, Brière C, Bécard G, Dénarié J, Gough C (August 2005). <a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fj.1365-313X.2005.02522.x">"Nod factors and a diffusible factor from arbuscular mycorrhizal fungi stimulate lateral root formation in Medicago truncatula via the DMI1/DMI2 signalling pathway"</a>. <i>The Plant Journal</i>. <b>44</b> (2): <span class="nowrap">195–</span>207. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<span class="id-lock-free" title="Freely accessible"><a rel="nofollow" class="external text" href="https://doi.org/10.1111%2Fj.1365-313X.2005.02522.x">10.1111/j.1365-313X.2005.02522.x</a></span>. <a href="PMID_(identifier)" class="mw-redirect" title="PMID (identifier)">PMID</a> <a rel="nofollow" class="external text" href="https://pubmed.ncbi.nlm.nih.gov/16212600">16212600</a>.</cite></span>

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<li id="cite_note-8"><span class="mw-cite-backlink"><b><a href="#cite_ref-8">^</a></b></span> <span class="reference-text"><cite id="CITEREFGoversMoermanDownieHooykaas1986" class="citation journal cs1">Govers F, Moerman M, Downie JA, Hooykaas P, Franssen HJ, Louwerse J, van Kammen A, Bisseling T (October 1986). "Rhizobium nod genes are involved in inducing an early nodulin gene". <i>Nature</i>. <b>323</b> (6088): <span class="nowrap">564–</span>466. <a href="Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1986Natur.323..564G">1986Natur.323..564G</a>. <a href="Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1038%2F323564a0">10.1038/323564a0</a>. <a href="S2CID_(identifier)" class="mw-redirect" title="S2CID (identifier)">S2CID</a> <a rel="nofollow" class="external text" href="https://api.semanticscholar.org/CorpusID:4324682">4324682</a>.</cite></span>

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