momilactone-b and jasmonic-acid

Plant second metabolites momilactone A and B, which act as potent phytoalexins and allelochemicals, have been found thus far only in rice and the moss Hypnum plumaeforme, although both plants are taxonomically quite distinct. The concentrations of momilactone A and B, respectively, in rice plants were 4.5-140 and 2.9-85μg/g, and those in H. plumaeforme were 8.4-58.7 and 4.2-23.4μg/g. Momilactone A and B concentrations in rice and H. plumaeforme plants were increased by UV irradiation, elicitor and jasmonic acid treatments. Rice and H. plumaeforme plants secrete momilactone A and B into the rhizosphere, and the secretion level was also increased by UV irradiation, elicitor and jasmonic acid treatments. In addition, although endogenous concentrations of momilactone A in rice and H. plumaeforme were greater than those of momilactone B, the secretion levels of momilactone B were greater than those of momilactone A in rice and H. plumaeforme, which suggests that momilactone B may be selectively secreted by both rice and H. plumaeforme. As momilactone A and B exert potent antifungal and growth inhibitory activities, momilactone A and B may play an important role in the defense responses in H. plumaeforme and rice against pathogen infections and in allelopathy. The secretion of momilactone A and B into the rhizosphere may also prevent bacterial and fungal infections and provide a competitive advantage for nutrients through the inhibition of invading root systems of neighboring plants as allelochemicals. Therefore, both plants, despite their evolutionary distance, may use same defense strategy with respect to the momilactone A and B production and secretion, which resulting from convergent or parallel evolutionary processes. In the case of parallel evolution, there may be plant species providing the missing link in molecular evolution of momilactones between H. plumaeforme and rice.

Topics: Bryopsida; Cantharidin; Cyclopentanes; Diterpenes; Enzyme Inhibitors; Evolution, Molecular; Lactones; Oryza; Oxylipins; Pheromones; Plant Growth Regulators; Plant Immunity; Rhizosphere; Ultraviolet Rays

Momilactone A and B have been found only in rice and the moss, Hypnum plumaeforme, although both plants are taxonomically quite distinct. The endogenous concentrations of momilactone A and B in H. plumaeforme were 58.7 and 24.3 microg/g dry weight, respectively. UV-irradiation increased the concentrations of momilactone A and B. The concentrations of momilactone A and B, respectively, became 14- and 15-fold greater than those of non-UV-irradiated control. CuCl2 and FeCl2 (1 mmol/L) treatments also increased momilactone A and B concentrations by 2.7- to 6.1-fold and 2.9- to 6.3-fold, respectively. In addition, the protein phosphatase inhibitor, cantharidin, and jasmonic acid increased momilactone A and B concentrations in H. plumaeforme. Cantharidin acts as an elicitor and jasmonic acid is an important signaling molecule regulating inducible defense genes against the pathogen infection. Momilactone A and B, respectively, were increased 12- and 11-fold by 200 micromol/L cantharidin, and 14- and 15-fold by 100 micromol/L jasmonic acid compared with non-treated controls. As momilactone A and B are phytoalexins, these compounds may play an important role in defense responses against biotic and abiotic stress conditions in H. plumaeforme.

Topics: Bryopsida; Cantharidin; Cyclopentanes; Diterpenes; Enzyme Inhibitors; Gene Expression Regulation, Plant; Lactones; Metals; Oxylipins; Ultraviolet Rays