“Fairy rings” is the phenomenon in which turfgrass grows or dies in a circle. In previous reports, we discovered that fairy rings were induced by 2-azahypoxanthine (AHX) and imidazole-4-carboxamide (ICA) produced by one of the fairy rings forming fungi, Lepista sordida. AHX is metabolized to 2-aza-8-oxohypoxanthine (AOH) in plants. AHX, ICA and AOH are named fairy chemicals (FCs). Furthermore, we proved the existence of endogenous FCs and succeed in isolation and structural determination of some metabolites of FCs. Thus, we thought that the pathway producing them in plants was a novel purine pathway. However, the biosynthetic pathway of FCs in plants has not been disclosed completely. The precursor of FCs in chemically synthesis is 5-aminoimidazole-4-carboxamide (AICA) and we have found AHX is biosynthesized from AICA in plants. In feeding experiments with stable isotope-labeled AICA, it was revealed that ICA was also biosynthesized from AICA in plants. Furthermore, we developed a new detection and quantification method of FCs and succeed in quantification the endogenous content of that. In addition, by using this method, we found that FCs metabolites (two kinds of AOH-β-D-glucosides, ICA-riboside, and ICA-ribotide) endogenously exist in rice. AHX-ribotide, presumptive precursor of AHX, is chemically synthesized from AICA-ribotide and NO donor (NOC5). We found that AHX-ribotide was converted from AHX by hypoxanthine-guanine phosphoribosyltransferase obtained from rice, and a novel compound, AOH-ribotide, was also converted from AOH by the enzyme.
