DIFFERENTIAL INDUCTION OF LIPOXYGENASE ISOFORMS IN WHEAT UPON TREATMENT WITH RUST FUNGUS ELICITOR, CHITIN OLIGOSACCHARIDES, CHITOSAN, AND METHYL JASMONATE

A glycopeptide elicitor prepared from germ tubes of the rust fungus Pu ccinia graminis Pers. f. sp. tritici Erikss. & Henn (Pgt), as well as chitin oligosaccharides, chitosan, and methyl jasmonate (MI) stimulate d lipoxygenase (LOX) activity (E.C. 1.13.11.12) in wheat (Triticum aes tivum) leaves. Immunoblot analysis using anti-LOX antibodies revealed the induction of 92- and 103-kD LOX species after Pgt elicitor treatme nt. In contrast, MJ treatment led to a significant increase of a 100-k D LOX species, which was also detected at lower levels in control plan ts. The effects of chitin oligomers and chitosan resembled those cause d by MJ. In conjunction with other observations the results suggest th at separate reaction cascades exist, and that jasmonates may not be in volved in Pgt elicitor action. LOX-92 appears to be mainly responsible for the increase in LOX activity after Pgt elicitor treatment because its appearance on western blots coincided with high LOX activity in d istinct anion-exchange chromatography fractions. It is most active at pH 5.5 to 6.0, and product formation from linoleic and alpha-linolenic acid is clearly in favor of the 9-LOOHs. It is interesting that a 92- kD LOX species, which seems to correspond to the Pgt elicitor-induced LOX species, was also detected in rust-inoculated leaves.