Induced accumulation of 2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one glucoside (HDMBOA-Glc) in maize leaves

Accumulation of 2-(2-hydroxy-4,7-dimethoxy-1,4-benzoxazin-3-one)-beta -D-glucopyranose (HDM BOA-Glc) was induced in maize leaves by treatment with CuCl2, chitopentaose, penta-N-acetylchitopentaose, or jasmonic acid (JA). The accumulation of HDMBOA-Glc was accompanied by a decrease in level of 2-(2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one)-beta -D-glucopyranose (DIMBOA-Glc). When the leaf segments were treated with JA in the presence of [Me-H-2(3)]L-methionine, the label was efficiently incorporated into HDMBOA-Glc, while no incorporation into DIMBOA-Glc or HMBOA-Glc was detected, suggesting the conversion of constitutive DIMBOA-Glc to HDMBOA-Glc by methylation at the 4-position. Levels of endogenous 5.4 and its leucine conjugate transiently increased prior to the accumulation of HDMBOA-Glc in leaf segments treated with CuCl2 and chitopentaose. The lipoxygenase inhibitor ibuprofen suppressed the accumulation of HDMBOA-Glc induced by CuCl2 treatment, and the reduced accumulation of HDMBOA-Glc was recovered by addition of JA. These findings suggested that JA functions as a signal transducer in the induction of HDMBOA-Glc accumulation. (C) 2001 Elsevier Science Ltd. All rights reserved.