Differential effects of methyl jasmonate on the expression of the early light-inducible proteins and other light-regulated genes in barley

The effects of methyl jasmonate (JA-Me) on early light-inducible protein (E LIP) expression in barley (Hordeum vulgare L. cv Apex) have been studied. T reatment of leaf segments with JA-Me induces the same symptoms as those exh ibited by norflurazon bleaching, including a loss of pigments and enhanced light stress that results in increased ELIP expression under both high- and low-light conditions. The expression of both low-and high-molecular-mass E LIP families is considerably down-regulated by JA-Me at the transcript and protein levels. This repression occurs despite increased photoinhibition me asurable as a massive degradation of D1 protein and a delayed recovery of p hotosystem II activity. In TA-Me-treated leaf segments, the decrease of the photochemical efficiency of photosystem II under high light is substantial ly more pronounced as compared to controls in water. The repression of ELIP expression by TA-Me is superimposed on the effect of the increased light s tress that leads to enhanced ELIP expression. The fact that the reduction o f ELIP transcript levels is less pronounced than those of light-harvesting complex II and small subunit of Rubisco transcripts indicates that light st ress is still affecting gene expression in the presence of JA-Me. The jasmo nate-induced protein transcript levels that are induced by JA-Me decline un der light stress conditions.