S. Reinbothe et al., METHYL JASMONATE REPRESSES TRANSLATION INITIATION OF A SPECIFIC SET OF MESSENGER-RNAS IN BARLEY, Plant journal, 4(3), 1993, pp. 459-467
Jasmonic acid methyl ester (methyl jasmonate, JaMe) causes accumulatio
n of novel abundant proteins in excised leaf segments of barley, and c
oncomitantly represses synthesis of most pre-existing ('control') prot
eins. The changes in control protein synthesis do not correspond to eq
uivalent alterations at the in vitro translatable mRNA level, suggesti
ng a post-transcriptional mode of regulation. Methyl jasmonate did not
interfere with the in vitro translation of either control or JaMe-ind
uced mRNAs. Polysome runoff translation, in combination with two-dimen
sional separations of the products formed, however, revealed a reduced
synthesis of control proteins in JaMe-exposed leaf tissues, in contra
st to a continued translation of these polypeptides in water-treated l
eaf segments. In vitro translation of polysomal RNAs demonstrated the
preferential association of control mRNAs with polysomes of water-trea
ted leaf tissues but not with polysomes of JaMe-treated tissues. Polys
omes isolated from the latter leaves contained primarily JaMe-induced
mRNAs, as shown by in vitro translation and Northern hybridization wit
h gene-specific probes. Treatment of JaMe-incubated leaf tissues,with
cycloheximide prior to harvesting caused an increase of in vitro trans
latable control mRNAs recovered from polysomes, thus highlighting an i
mpairment of control protein synthesis by JaMe at the level of transla
tion initiation.