ABSTRACT
Osmotic stress induces several senescence-like processes in leaves, such as specific changes in gene expression and yellowing. These processes are dependent on the accumulation of jasmonates and on intact jasmonate signaling. This chapter describes the treatment of Arabidopsis thaliana leaves with sorbitol as an osmotic stress agent and the determination of the elicited phenotypes encompassing chlorophyll loss, degradation of plastidial membrane lipids, and induction of genes regulated by senescence and jasmonate.
Subject(s)
Arabidopsis/physiology , Cyclopentanes/metabolism , Oxylipins/metabolism , Phenotype , Plant Growth Regulators/physiology , Plant Leaves/physiology , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Chlorophyll/isolation & purification , Chlorophyll/metabolism , Diglycerides/chemistry , Diglycerides/isolation & purification , Diglycerides/metabolism , Gene Expression , Gene Expression Profiling , Gene Expression Regulation, Plant , Membrane Lipids/chemistry , Membrane Lipids/isolation & purification , Membrane Lipids/metabolism , Osmotic Pressure , Plastids/metabolism , Signal Transduction , Sorbitol/pharmacologyABSTRACT
Jasmonic acid and derivatives are oxylipin signaling compounds derived from linolenic acid. Jasmonates accumulate during natural and dark-induced senescence but the increase in these compounds is not essential for the initiation or progression of these senescence processes. Here we report that during natural and dark-induced senescence the increase in jasmonate levels does not trigger jasmonate signaling. Furthermore we provide evidence that jasmonate production might result from membrane turnover during dark-induced senescence.
Subject(s)
Arabidopsis/metabolism , Cyclopentanes/metabolism , Oxylipins/metabolism , Signal Transduction/physiology , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Esterification , Gene Expression Regulation, Plant/drug effects , Gene Expression Regulation, Plant/radiation effects , Light , Plant Leaves/metabolism , Sorbitol/pharmacology , Time , Time Factors , alpha-Linolenic Acid/metabolismABSTRACT
Jasmonic acid and related oxylipins are controversially discussed to be involved in regulating the initiation and progression of leaf senescence. To this end, we analyzed profiles of free and esterified oxylipins during natural senescence and upon induction of senescence-like phenotypes by dark treatment and flotation on sorbitol in Arabidopsis (Arabidopsis thaliana). Jasmonic acid and free 12-oxo-phytodienoic acid increased during all three processes, with the strongest increase of jasmonic acid after dark treatment. Arabidopside content only increased considerably in response to sorbitol treatment. Monogalactosyldiacylglycerols and digalactosyldiacylglycerols decreased during these treatments and aging. Lipoxygenase 2-RNA interference (RNAi) plants were generated, which constitutively produce jasmonic acid and 12-oxo-phytodienoic acid but do not exhibit accumulation during natural senescence or upon stress treatment. Chlorophyll loss during aging and upon dark incubation was not altered, suggesting that these oxylipins are not involved in these processes. In contrast, lipoxygenase 2-RNAi lines and the allene oxid synthase-deficient mutant dde2 were less sensitive to sorbitol than the wild type, indicating that oxylipins contribute to the response to sorbitol stress.
