Identification of reaction products of 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienoic acid (KODA) and norepinephrine that strongly induce flowering in Lemna

The reaction of 9-hydroxy-10-oxo-12(Z),15(Z)-octadecadienoic acid (KODA) and catecholamine in water (pH 8.0) in vitro generates many products, and we have shown that the major adduct FN1 among the reactants of KODA and norepinephrine is a potent inducer of floral differentiation in Lemna (L.) paucicostata 151 [Yokoyama et al. (2000) Plant Cell Physiol 41: 110 113, Yamaguchi et al. (2001) ibid 42: 1201-1209]. Since such reactants may be involved ill flower induction ill vivo, it is of interest to elucidate the structure-activity relationships among the reactants to throw light oil the nature of the putative active site. Here, we report two other adducts, designated as FN7 and FN10. They are structurally similar to FN1, having a tricyclic structure with 12-cis-olefin Conjugated with noradrenochrorne. FN10 was a more potent inducer than FN1. These results are consistent with the hypothesis that tricyclic KODA/norepinephrine adducts play an important role in flower-induction in L. paucicostata, strain 151.