chlorophyll-a and 12-oxophytodienoic-acid

Little is known regarding production and function of endogenous jasmonates (JAs) in root nodules of soybean plants inoculated with Bradyrhizobium japonicum. We investigated (1) production of jasmonic acid (JA) and 12-oxophytodienoic acid (OPDA) in roots of control and inoculated plants and in isolated nodules; (2) correlations between JAs levels, nodule number, and plant growth during the symbiotic process; and (3) effects of exogenous JA and OPDA on nodule cell number and size. In roots of control plants, JA and OPDA levels reached a maximum at day 18 after inoculation; OPDA level was 1.24 times that of JA. In roots of inoculated plants, OPDA peaked at day 15, whereas JA level did not change appreciably. Shoot dry matter of inoculated plants was higher than that of control at day 21. Chlorophyll a decreased more abruptly in control plants than in inoculated plants, whereas b decreased gradually in both cases. Exogenous JA or OPDA changed number and size of nodule central cells and peripheral cells. Findings from this and previous studies suggest that increased levels of JA and OPDA in control plants are related to senescence induced by nutritional stress. OPDA accumulation in nodulated roots suggests its involvement in "autoregulation of nodulation."

Topics: Adult; Bradyrhizobium; Chlorophyll; Chlorophyll A; Cyclopentanes; Fatty Acids, Unsaturated; Glycine max; Humans; Oxylipins; Plant Growth Regulators; Plant Roots; Plant Shoots; Root Nodules, Plant; Symbiosis

Jasmonate (JA) activates plant defense, promotes pollen maturation, and suppresses plant growth. An emerging theme in JA biology is its involvement in light responses; here, we examine the interdependence of the JA- and light-signaling pathways in Arabidopsis thaliana. We demonstrate that mutants deficient in JA biosynthesis and signaling are deficient in a subset of high irradiance responses in far-red (FR) light. These mutants display exaggerated shade responses to low, but not high, R/FR ratio light, suggesting a role for JA in phytochrome A (phyA) signaling. Additionally, we demonstrate that the FR light-induced expression of transcription factor genes is dependent on CORONATINE INSENSITIVE1 (COI1), a central component of JA signaling, and is suppressed by JA. phyA mutants had reduced JA-regulated growth inhibition and VSP expression and increased content of cis-(+)-12-oxophytodienoic acid, an intermediate in JA biosynthesis. Significantly, COI1-mediated degradation of JASMONATE ZIM DOMAIN1-beta-glucuronidase (JAZ1-GUS) in response to mechanical wounding and JA treatment required phyA, and ectopic expression of JAZ1-GUS resulted in exaggerated shade responses. Together, these results indicate that JA and phyA signaling are integrated through degradation of the JAZ1 protein, and both are required for plant responses to light and stress.

Topics: Anthocyanins; Arabidopsis; Arabidopsis Proteins; Chlorophyll; Cyclopentanes; Fatty Acids, Unsaturated; Flowers; Gene Expression Regulation, Plant; Light; Mutation; Oxylipins; Phytochrome A; Plant Growth Regulators; RNA, Plant; Signal Transduction

Pathogen infection leads to defence induction as well as to changes in carbohydrate metabolism of plants. Salicylic acid and oxylipins are involved in the induction of defence, but it is not known if these signalling molecules also mediate changes in carbohydrate metabolism. In this study, the effect of application of salicylic acid and the oxylipins 12-oxo-phytodienoic acid (OPDA) and jasmonic acid on photosynthesis was investigated by kinetic chlorophyll fluorescence imaging and compared with the effects of infection by virulent and avirulent strains of Pseudomonas syringae. Both pathogen strains and OPDA caused a similar change in fluorescence parameters of leaves of Arabidopsis thaliana. The response to OPDA appeared faster compared with that to the pathogens and persisted only for a short time. Infiltration with jasmonic acid or salicylic acid did not lead to a localized and distinct fluorescence response of the plant. To capture the faint early symptoms of the plant response, a novel algorithm was applied identifying the unique fluorescence signature-the set of images that, when combined, yield the highest contrast between control and infected leaf segments. Unlike conventional fluorescence parameters, this non-biased approach indeed detected the infection as early as 6 h after inoculation with bacteria. It was posssible to identify distinct fluorescence signatures characterizing the early and late phases of the infection. Fluorescence signatures of both infection phases were found in leaves infiltrated with OPDA.

Topics: Arabidopsis; Chlorophyll; Cyclopentanes; Fatty Acids, Unsaturated; Fluorescence; Host-Parasite Interactions; Oxylipins; Plant Leaves; Pseudomonas syringae; Virulence

In this work, the role of jasmonic acid (JA) in leaf senescence is examined. Exogenous application of JA caused premature senescence in attached and detached leaves in wild-type Arabidopsis but failed to induce precocious senescence of JA-insensitive mutant coi1 plants, suggesting that the JA-signaling pathway is required for JA to promote leaf senescence. JA levels in senescing leaves are 4-fold higher than in non-senescing ones. Concurrent with the increase in JA level in senescing leaves, genes encoding the enzymes that catalyze most of the reactions of the JA biosynthetic pathway are differentially activated during leaf senescence in Arabidopsis, except for allene oxide synthase, which is constitutively and highly expressed throughout leaf development. Arabidopsis lipoxygenase 1 (cytoplasmic) expression is greatly increased but lipoxygenase 2 (plastidial) expression is sharply reduced during leaf senescence. Similarly, AOC1 (allene oxide cyclase 1), AOC2, and AOC3 are all up-regulated, whereas AOC4 is down-regulated with the progression of leaf senescence. The transcript levels of 12-oxo-PDA reductase 1 and 12-oxo-PDA reductase 3 also increase in senescing leaves, as does PED1 (encoding a 3-keto-acyl-thiolase for beta-oxidation). This represents the first report, to our knowledge, of an increase in JA levels and expression of oxylipin genes during leaf senescence, and indicates that JA may play a role in the senescence program.

Topics: Acetyl-CoA C-Acetyltransferase; Arabidopsis; Chlorophyll; Cyclopentanes; Defensins; Fatty Acids, Unsaturated; Gene Expression Regulation, Developmental; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Intramolecular Oxidoreductases; Lipoxygenase; Mutation; Oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors; Oxylipins; Plant Leaves; Plant Proteins; Signal Transduction; Up-Regulation