title: Synergistic effect of deoxyanthocyanins from symbiotic fern Azolla spp. on hrmA gene induction in the cyanobacterium Nostoc punctiforme.
abstract: The hrmA gene of the N2-fixing cyanobacterium Nostoc punctiforme functions in repressing the formation of transitory motile filaments, termed hormogonia, by plant-associated vegetative filaments. Here, we report that anthocyanins can contribute to induction of hrmA expression. Aqueous extract from fronds of the fern Azolla pinnata, a host of symbiotic Nostoc spp., was found to be a potent inducer of hrmA-luxAB in N. punctiforme strain UCD 328. The hrmA-luxAB inducing activities of A. pinnata, as well as Azolla filiculoides, were positively correlated with levels of frond deoxyanthocyanins. Analyses of the deoxyanthocyanins in frond extracts revealed, in order of predominance, an acetylated glycoside derivative of luteolinidin (m/z 475) and of apigeninidin (m/z 459) and minor amounts of a second luteolinidin derivative. At up to 150 microM, a purified preparation of deoxyanthocyanins only weakly induced hrmA-luxAB on its own, but mixtures with hrmA-luxAB inducers (A. filiculoides extract or the flavonoid naringin) synergistically doubled to tripled their inducing activities. These results suggest that appropriately localized deoxyanthocyanins could function in plant-mediated mechanisms for repressing Nostoc spp. hormogonium formation.
authors.affiliation: Laboratory of Cell and Functional Biology, Faculty of Science, University of the Ryukyus, Nishihara, Okinawa, Japan.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Cohen
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Sakihama
authors.forename: Yojiro C
authors.initials: YC
authors.lastname: Takagi
authors.forename: Toshio
authors.initials: T
authors.lastname: Ichiba
authors.forename: Hideo
authors.initials: H
authors.lastname: Yamasaki
mesh_terms: D000872:Anthocyanins / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D047310:Apigenin; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D000458:Cyanobacteria / Q000235:genetics*; D004357:Drug Synergism; D029624:Ferns / Q000737:chemistry*; D044950:Flavanones; D005419:Flavonoids / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D009586:Nitrogen Fixation / Q000235:genetics; D010936:Plant Extracts / Q000494:pharmacology; D013559:Symbiosis; D015533:Transcriptional Activation; D000094162:Phytoalexins
chemical_list: D000872:Anthocyanins; D047310:Apigenin; D001426:Bacterial Proteins; D044950:Flavanones; D005419:Flavonoids; D008156:Luciferases; D010936:Plant Extracts; C085100:hrmA protein, Pseudomonas syringae; C104027:apigeninidin; D000094162:Phytoalexins; C005274:naringin