U. Schaffrath et al., Characterization of RCI-1, a chloroplastic rice lipoxygenase whose synthesis is induced by chemical plant resistance activators, EUR J BIOCH, 267(19), 2000, pp. 5935-5942
A full-length lipoxygenase cDNA (RCI-1) has been cloned from rice (Oryza sa
tiva) whose corresponding transcripts accumulate in response to treatment o
f the plants with chemical inducers of acquired resistance such as benzo(1,
2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH), 2,6-dichloroisonic
otinic acid (INA), and probenazol. In contrast, RCI-1 transcript levels did
not increase after inoculation with compatible and incompatible races of t
he rice blast fungus Magnaporthe grisea and the nonhost pathogen Pseudomona
s syringae pv. syringae. RCI-1 transcript levels also increased after exoge
nous application of jasmonic acid, but not upon wounding. Dose-response and
time course experiments revealed a similar pattern of transcript accumulat
ion and lipoxygenase activity in BTH-treated rice leaves. Enzymatic analysi
s of recombinant RCI-1 protein produced in Escherichia coli revealed that 1
3-hydroperoxy-octadecanoic acids were the predominant reaction products whe
n either linoleic or linolenic acid used as a substrate. The RCI-1 sequence
features a putative chloroplast targeting sequence at its N-terminus. Inde
ed, a protein consisting of the putative chloroplast transit peptide fused
to green fluorescent protein was exclusively localized in chloroplasts, ind
icating that RCI-1 is a chloroplastic enzyme.