Jasmonate Levels Research Articles

Occurrence and identification of jasmonic acid and its amino acid conjugates induced by osmotic stress in barley leaf tissue

The effect of osmotically active substances on the alteration of endogenous jasmonates was studied in barley (Hordeum vulgare L. cv. Salome) leaf tissue. Leaf segments were subjected to solutions of d-sorbitol, d-mannitol, polyethylene glycol 6000, sodium chloride, or water as a control. Alterations of endogenous jasmonates were monitored qualitatively and quantitatively using immunoassays. The structures of jasmonates isolated were determined on the basis of authentic substances by capillary gas chromatography-mass spectrometry. The stereochemistry of the conjugates was confirmed by high performance liquid chromatography with diastereoisomeric references. In barley leaves, jasmonic acid and its amino acid conjugates, for example, with valine, leucine, and isoleucine, are naturally occurring jasmonates. In untreated leaf segments, only low levels of these native jasmonates were found. After treatment of the leaf tissues with sorbitol, mannitol, as well as with polyethylene glycol, an increase of both jasmonic acid and its conjugates could be observed, depending on the stress conditions used. In contrast, salt stress was without any stimulating effect on the levels of endogenous jasmonates. From barley leaf segments exposed to sorbitol (1m) for 24 h, jasmonic acid was identified as the major accumulating compound. Jasmonic acid-amino acid conjugates increased likewise upon stress treatment.

Evidence for the involvement of jasmonates and their octadecanoid precursors in the tendril coiling response of Bryonia dioica

The structural requirements of jasmonates to induce tendril coiling in Bryonia dioica were investigated. 9,10-Dihydromethyljasmonate, the 6-hydroxy analogues of methyljasmonate and dihydromethyljasmonate as well as 6-desoxyjasmonates were inactive up to 0.1 mM concentration, whereas methyljasmonate (JAME) was highly active at 5–10 μM (threshold: 1 μM) concentration. All biosynthetic precursors of jasmonic acid (α-linolenic acid, 13-hydroperoxylinolenic acid and 12-oxo-phytodienoic acid (PDA) tested were biologically active. The methyl ester of PDA (PDAME) was the most active inducer, with relative activities: PDAME, JAME, 13-hydroperoxylinolenic acid ∼ α-linolenic acid. The response to PDAME was also much more rapid than that to JAME. Fatty acid analysis of tendril tissue showed the presence of α-linolenic acid in membrane lipids, including plasma membranes. Shortly after a touch stimulus, the cellular pool of free α-linolenic acid drops faster than that of other fatty acids suggesting a preferential requirement for this fatty acid. Jasmonic acid (JA) is present in leaf and tendril extracts of B. dioica, as shown using a highly sensitive and selective LC-HPLC-ELISA technique based on the monoclonal anti-(−)-JAME antibody JAH1-8B4-2A11 [limit of detection < 1 pmol (−)-JAME]. Coiling elicited with JAME or indole-3-acetic acid proceeded with increased ethylene evolution. Aminoethoxyvinylglycine inhibited this ethylene formation to below levels of controls without any effect on coiling. Collectively, our data support the view that touch rapidly initiates in B. dioica tendrils the formation of jasmonates from α-linolenic acid which are released as messengers triggering the coiling response. Specific sites (receptors) for the recognition of jasmonates have to be postulated in order to explain the high structural selectivity of the response. The finding that PDAME acts considerably faster and at much lower levels than JAME suggests that it either reaches the precise location of jasmonate formation in the cell more easily than JAME itself giving rise to high local jasmonate levels or that PDAME is by itself an active inducer of tendril coiling.

Expression, Activity, and Cellular Accumulation of Methyl Jasmonate-Responsive Lipoxygenase in Soybean Seedlings

Exposure of soybean (Glycine max) seedlings to low levels of atmospheric methyl jasmonate induced the expression and accumulation of one or more lipoxygenase(s) in the primary leaves, hypocotyls, epicotyls, and cotyledons. In the primary leaf, the major site of lipoxygenase accumulation in response to methyl jasmonate was in the vacuoles of paraveinal mesophyll cells. In the other organs, however, most of the methyl jasmonate-responsive lipoxygenase(s) were associated with both the epidermal and cortical cells and were present in both vacuoles and plastids. In plastids, the methyl jasmonate-responsive lipoxygenase was sequestered into protein inclusion bodies; no lipoxygenase was evident in either the thylakoids or the stroma. Both spectrophotometric measurement of conjugated diene formation and thin layer chromatography of lipoxygenase product formation indicated that methyl jasmonate caused an increase in the amount of lipoxygenase activity. Electron microscopy of the methyl jasmonate-responsive lipoxygenase protein in the vacuoles showed that it was arranged into a stellate, paracrystalline structure in various cell types other than the paraveinal mesophyll cells. The paracrystals appeared to be composed of tubular elements of between 5 and 8 nm in diameter, were of variable length, and were observed in most cell types of the seedling organs.

Coregulation of Soybean Vegetative Storage Protein Gene Expression by Methyl Jasmonate and Soluble Sugars

The soybean vegetative storage protein genes vspA and vspB are highly expressed in developing leaves, stems, flowers, and pods as compared with roots, seeds, and mature leaves and stems. In this paper, we report that physiological levels of methyl jasmonate (MeJA) and soluble sugars synergistically stimulate accumulation of vsp mRNAs. Treatment of excised mature soybean (Glycine max Merr. cv Williams) leaves with 0.2 molar sucrose and 10 micromolar MeJA caused a large accumulation of vsp mRNAs, whereas little accumulation occurred when these compounds were supplied separately. In soybean cell suspension cultures, the synergistic effect of sucrose and MeJA on the accumulation of vspB mRNA was maximal at 58 millimolar sucrose and was observed with fructose or glucose substituted for sucrose. In dark-grown soybean seedlings, the highest levels of vsp mRNAs occurred in the hypocotyl hook, which also contained high levels of MeJA and soluble sugars. Lower levels of vsp mRNAs, MeJA, and soluble sugars were found in the cotyledons, roots, and nongrowing regions of the stem. Wounding of mature soybean leaves induced a large accumulation of vsp mRNAs when wounded plants were incubated in the light. Wounded plants kept in the dark or illuminated plants sprayed with dichlorophenyldimethylurea, an inhibitor of photosynthetic electron transport, showed a greatly reduced accumulation of vsp mRNAs. The time courses for the accumulation of vsp mRNAs induced by wounding or sucrose/MeJA treatment were similar. These results strongly suggest that vsp expression is coregulated by endogenous levels of MeJA (or jasmonic acid) and soluble carbohydrate during normal vegetative development and in wounded leaves.

The Problem of Acquired Physiological Immunity in Plants

The Problem of Acquired Physiological Immunity in Plants