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. Jasmonic acid and its methyl ester, methyl jasmonate, are rapidly emerging as strong candidates for intracellular or intercellular messengers in higher plants. When applied directly to plants or suspension cultures, they produce a number of phytohormone-like effects (1,19,26,31 (27). In mammals, eicosanoids are synthesized following the release of arachidonic acid into the cytoplasm and function as intracellular stress messengers (27). Analogously, plant cells are able to utilize linolenic acid as a substrate for the lipoxygenase-dependent synthesis of jasmonic acid (30). Although it has yet to be definitively established that jasmonic acid or methyl jasmonate are intracellular messengers in plant systems, the results of Farmer and Ryan (3) suggest that they may be involved in a wound-responsive signal cascade.The expression and accumulation of soybean VSPs is regulated by jasmonic acid and methyl jasmonate (1,7,10,14,22,23). The VSPs consist of three proteins of 27, 29, and 94 kD (vsp27 or vspa, vsp29 or vsp#, and vsp94, respectively), which accumulate during vegetative growth in a specialized cell layer termed the PVM layer (5,6,8,11,13). The PVM layer apparently serves as a direct conduit from the palisade parenchyma to the phloem (4-6, 8). VSP transcripts and their proteins respond to the immediate need to store nitrogen or amino acids (22,34) and to the removal of sink tissue or pods (20,25,32,33). The VSPs decrease in abundance during seed development (21, 34). Apparently, the VSPs have been recruited for temporary storage of nitrogen during vegetative growth, and this nitrogen is later contributed to the developing seed.In soybean (Glycine max) seedlings, ...

The response of individual members of the lipoxygenase multigene family in soybeans to sink deprivation was analyzed. RNase protection assays indicated that a novel vegetative lipoxygenase gene, vlxC, and three other vegetative lipoxygenase mRNAs accumulated in mature leaves in response to a variety of sink limitations. These data suggest that several members of the lipoxygenase multigene family are involved in assimilate partitioning. The possible involvement of jasmonic acid as a signaling molecule regulating assimilate partitioning into the vegetative storage proteins and lipoxygenases was directly assessed by determining the endogenous level of jasmonic acid in leaves from plants with their pods removed. There was no rise in the level of endogenous jasmonic acid coincident with the strong increase in both vlxC and vegetative storage protein VspB transcripts in response to sink limitation. Thus, expression of the vegetative lipoxygenases and vegetative storage proteins is not regulated by jasmonic acid in sink-limited leaves.

The response of individual members of the lipoxygenase multigene family in soybeans to sink deprivation was analyzed. RNase protection assays indicated that a novel vegetative lipoxygenase gene, vlxC, and three other vegetative lipoxygenase mRNAs accumulated in mature leaves in response to a variety of sink limitations. These data suggest that several members of the lipoxygenase multigene family are involved in assimilate partitioning. The possible involvement of jasmonic acid as a signaling molecule regulating assimilate partitioning into the vegetative storage proteins and lipoxygenases was directly assessed by determining the endogenous level of jasmonic acid in leaves from plants with their pods removed. There was no rise in the level of endogenous jasmonic acid coincident with the strong increase in both vlxC and vegetative storage protein VspB transcripts in response to sink limitation. Thus, expression of the vegetative lipoxygenases and vegetative storage proteins is not regulated by jasmonic acid in sink-limited leaves.

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