Posttranscriptional control in the expression of the genes coding for high-light-regulated HL#2 proteins

An antibody was raised against the protein HL#2 which is a nuclear-encoded light-stress-induced protein of barley (Hordeum vulgare L.). The expression of the mRNA and the protein of HL#2 was determined under the influence of high light and methyl jasmonate. The mRNA of HL#2 was induced by high light (1800 &mgr;mol m(-2) s(-1) and 25 degrees C) and the steady-state levels remained elevated for up to 48 h of exposure to high-light stress. In contrast, using an antibody against HL#2 there was no observable change in the level of HL#2 proteins of 18 kDa and 15.5 kDa during the same treatment. These data indicate a pronounced stress-induced control of HL#2 expression at a post-transcriptional level. In the presence of methyl jasmonate (45 &mgr;M), the induction of HL#2 occurred together with that of the two most closely related jasmonate-inducible proteins (JIPs) of 32.6 and 32.7 kDa, as judged by their cross-reactivity with the antibody against HL#2. In contrast to the mRNA and protein levels of early light-inducible proteins (ELIPs) in green barley, those of HL#2 appeared not to be influenced by low temperatures. Therefore, the control of ELIPs and HL#2 by high light fluxes may be measured via the same photoreceptor but must, at least partially, be under the control of two divergent signal transduction chains.