Editing Capsaicin (section)

== Natural function ==
Capsaicin is present in large quantities in the [[Placentation#In plants|placental tissue]] (which holds the seeds), the internal membranes and, to a lesser extent, the other fleshy parts of the fruits of plants in the genus ''[[Capsicum]]''.  The seeds themselves do not produce any capsaicin, although the highest concentration of capsaicin can be found in the white [[Fruit anatomy#Mesocarp|pith]] of the inner wall, where the seeds are attached.<ref name="NMSU Q&A 2005">{{cite web| publisher = New Mexico State University – College of Agriculture and Home Economics |title=Chile Information – Frequently Asked Questions |year=2005 |url=http://spectre.nmsu.edu/dept/academic.html?i=1274&s=sub |access-date=17 May 2007 |archive-url = https://web.archive.org/web/20070504035555/http://spectre.nmsu.edu/dept/academic.html?i=1274&s=sub <!-- Bot retrieved archive --> |archive-date = 4 May 2007}}</ref>

The seeds of ''Capsicum'' plants are dispersed predominantly by birds. In birds, the [[TRPV1]] channel does not respond to capsaicin or related chemicals, but mammalian TRPV1 is very sensitive to it. This is advantageous to the plant, as chili pepper seeds consumed by birds pass through the digestive tract and can germinate later, whereas mammals have [[molar (tooth)|molar teeth]] that destroy such seeds and prevent them from germinating.<!-- Tewksbury & Nabhan 2001, Nature 412 -->  Thus, [[natural selection]] may have led to increasing capsaicin production because it makes the plant less likely to be eaten by animals that do not help it disperse.<ref name="Tewksbury Nabhan 2001">{{cite journal | vauthors = Tewksbury JJ, Nabhan GP | title = Seed dispersal. Directed deterrence by capsaicin in chilies | journal = Nature | volume = 412 | issue = 6845 | pages = 403–404 | date = July 2001 | pmid = 11473305 | doi = 10.1038/35086653 | bibcode = 2001Natur.412..403T | s2cid = 4389051 }}</ref> There is also evidence that capsaicin may have evolved as an [[Fungicide|anti-fungal]] agent.<ref>{{cite journal | vauthors = Tewksbury JJ, Reagan KM, Machnicki NJ, Carlo TA, Haak DC, Peñaloza AL, Levey DJ | title = Evolutionary ecology of pungency in wild chilies | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 105 | issue = 33 | pages = 11808–11811 | date = August 2008 | pmid = 18695236 | pmc = 2575311 | doi = 10.1073/pnas.0802691105 | title-link = doi | doi-access = free | bibcode = 2008PNAS..10511808T }}</ref> The fungal pathogen ''[[Fusarium]]'', which is known to infect wild chilies and thereby reduce seed viability, is deterred by capsaicin, which thus limits this form of predispersal seed mortality.

The [[vanillotoxin]]-containing venom of a certain [[tarantula]] species (''[[Psalmopoeus cambridgei]])'' activates the same pathway of pain as is activated by capsaicin, an example of a shared pathway in both plant and animal anti-mammalian defense.<ref name="auto">{{cite journal |vauthors=Siemens J, Zhou S, Piskorowski R, Nikai T, Lumpkin EA, Basbaum AI, King D, Julius D |date=November 2006 |title=Spider toxins activate the capsaicin receptor to produce inflammatory pain |journal=Nature |volume=444 |issue=7116 |pages=208–212 |bibcode=2006Natur.444..208S |doi=10.1038/nature05285 |pmid=17093448 |s2cid=4387600}}</ref>