Characterization of a hydroperoxide lyase gene and effect of C6-volatiles on expression of genes of the oxylipin metabolism in Citrus.
A number of C6-volatile products of the lipoxygenase (LOX) pathway was examined for their antifungal activity and a potential role as a signal molecule in citrus. trans-2-Hexenal induced the rough lemon lipoxygenase gene (RlemLOX), hydroperoxide lyase gene (RlemHPL) and AOS gene, but hexanal, and hexanol suppressed them. cis-3-Hexenol and trans-2-hexenol increased expression of the AOS gene but not RlemLOX and RlemHPL. Transcripts of the RlemHPL and AOS gene were detected constitutively in leaves by northern blot, but wounding or inoculation with nonpathogenic Alternaria alternata rapidly increased the transcript accumulation. Transcripts of the RlemHPL and AOS genes were also induced with pathogenic A. alternata, which produces the host-selective ACR-toxin, but the signal declined rapidly after inoculation. An increase in enzymatic activity of HPL after wounding or inoculation with nonpathogen was suppressed in leaves infected with the pathogen. Interestingly, vapor treatment with trans-2-hexenol delayed necrotic spot formation in the leaves inoculated with the pathogenic A. alternata. Since trans-2-hexenol has no antifungal activity to A. alternata and also did not inhibit necrosis formation by ACR-toxin alone, the delay of symptoms may be caused by activation of AOS in the LOX pathway to produce oxylipin derivatives such as methyl jasmonate for activation of defense related genes with antifungal activity.
Gomi
Kenji
K
Laboratory of Plant Pathology, Faculty of Agriculture, Department of Life Sciences, Kagawa University, Miki, Kagawa 761-0795, Japan.
Yamasaki
Yumiko
Y
Yamamoto
Hiroyuki
H
Akimitsu
Kazuya
K
D000446:Aldehyde-Lyases / Q000235:genetics*; D000528:Alternaria / Q000472:pathogenicity; D000595:Amino Acid Sequence; D001483:Base Sequence; D002957:Citrus / Q000187:drug effects* / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D003001:Cloning, Molecular; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D000441:Hexanols / Q000494:pharmacology*; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism / Q000382:microbiology; D011994:Recombinant Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid
D018076:DNA, Complementary; D018744:DNA, Plant; D000441:Hexanols; D011994:Recombinant Proteins; D003577:Cytochrome P-450 Enzyme System; D000446:Aldehyde-Lyases; C054540:hydroperoxide lyase