Naturally occuring modifiers of auxin-receptor interaction in corn: Identification as benzoxazolinones.

A naturally-occurring material termed 'supernatant factor' [Ray, P.R., Dohrmann, U., Hertel, R.: Plant Physiol. 59. 357-364 (1977)], which has the property of modifying the binding affinity of auxins to receptor sites, has been isolated from corn (Zea mays L.) and characterised as a mixture of 6-methoxy-2-benzoxazolinone (MBOA) and 6,7-dimethoxy-2-benzoxazolinone (DMBOA). DMBOA is about 50 times more active than MBOA in inhibiting binding of the auxin 1-naphthylacetic acid to membrane-bound or solubilised receptors. The activity of these compounds and the parent analogue in inhibiting auxin binding is correlated with their ability to inhibit auxin-induced growth.