Secretion of momilactone A and B by the moss Hypnum plumaeforme.

Nevertheless both plants are taxonomically quite distinct, momilactone A and B have been found only in rice and the moss, Hypnum plumaeforme which often forms large pure colonies. But biological meanings of momilactone A and B in H. plumaeforme is unknown. UV-irradiation induced a 15- and 16-fold increase in the secretion level of momilactone A and B, respectively, by H. plumaeforme into the growth medium. Jasmonic acid and the protein phosphatase inhibitor, cantharidin, also increased the momilactone A and B secretion levels by 12- to 15-fold. Cantharidin acts as an elicitor, jasmonic acid is an important signaling molecule regulating inducible defense genes against the pathogen infections. Therefore, elicitor and/or pathogen attacks may increase the secretion of momilactone A and B. As momilactone A and B are phytoalexic and allelopathic, the increasing secretion of momilactone A and B may be associated with the activation of the defense responses of H. plumaeforme in the rhizosphere where plants must compete with invading root systems of neighboring plants and prevent from bacteria and fungi infections. Momilactone A and B may be able to prevent H. plumaeforme from pathogen infections and help competition with neighboring plants resulting in the formation of pure colonies.