Project description:Low reduced red:far-red ratio [R:FR] signaling through phytochromes induces shade avoidance responses, including petiole elongation. Jasmonic acid-mediated defense against herbivores and pathogens is inhibited under these conditions. Using microarrays we studied the crosstalk between low R:FR and JA at the global gene expression level in Arabidopsis thaliana.
Project description:The goal of this work was to investigate oxidative stress responses of Arabidopsis to low red to far-red ratios of light as a signal of competition using a biological weedy and an artificial source of far-red light. More specifically, elucidation of the signaling role of singlet oxygen in Arabidopsis under low red-to far-red light environments was the major objective of this work. Oxidative stress responses of Arabidopsis to low red (R) to far-red (FR) signals (R:FR ≈ 0.3), generated by a biological weedy and an artificial source of FR light, were compared with a weed-free control (R:FR ≈1.4). In the low R:FR treatments, induction of the shade avoidance responses coincided with increased singlet oxygen (1O2) production and decreased level of superoxide and superoxide dismutase activity. Although the increase of 1O2 was not due to protochlorophyllide accumulation and did not result in cell death, treatments with the 1O2 generator 5-aminolevulinic acid increased sensitivity to cell death. Transcriptome responses minimally resembled those reported in four Arabidopsis 1O2 generating systems such that only few genes (6 out of 1931) were consistently up-regulated supporting the specificity of 1O2 signaling. Moreover, suppressors of jasmonate accumulation, including the 1O2-responsive amidohydrolase ILL6, the sulfotransferase ST2a, which are involved in prioritization of elongation growth versus defense were consistently up-regulated. Our data support a model in which photoreceptors connect low R:FR light cues to the JA signaling pathway. Repression of bioactive JAs via the amidohydrolase ILL6, and sulfotransferase ST2a may promote the shade avoidance (versus defense) and 1O2 acclimation (versus cell death) responses to competition cues.
Project description:This SuperSeries is composed of the following subset Series: GSE30711: ChIP-Seq data from Arabidopsis thaliana under dark and far-red light GSE30712: Expression data from Arabidopsis thaliana under dark and far-red light Refer to individual Series
Project description:Low reduced red:far-red ratio [R:FR] signaling through phytochromes induces shade avoidance responses, including petiole elongation. Jasmonic acid-mediated defense against herbivores and pathogens is inhibited under these conditions. Using microarrays we studied the crosstalk between low R:FR and JA at the global gene expression level in Arabidopsis thaliana. Plants were exposed for 2 h. to the following treatments: high R/FR with mock spray, low R/FR with mock spray, high R/FR with JA spray, low R/FR with JA spray. Gene expression was determined in petioles.
Project description:This experiment was a time course performed over 24 hours to look at the effects on gene expression of exposure to low red:far-red ratio light in Arabidopsis thaliana plants. In this way genes involved in the shade avoidance response might be identified. This experiment was designed for gene identification only and containes no replicates,genes identified were verified by quantitative PCR for publication.
Project description:Plants grown at high densities perceive a decrease in the red to far-red (R:FR) ratio of incoming light, resulting from absorption of red light by canopy leaves and reflection of far-red light from neighboring plants. These changes in light quality trigger a series of responses known collectively as the shade avoidance syndrome. During shade avoidance, stems elongate at the expense of leaf and storage organ expansion, there is reduced branching, and flowering is accelerated. We identified several loci in Arabidopsis, mutations in which lead to plants defective in multiple shade avoidance outputs. Here we describe SAV3, an aminotransferase, and show that SAV3 catalyzes the formation of indole-3-pyruvic acid (IPA) from L-tryptophan (L-Trp), the first step in a previously proposed, but uncharacterized, auxin biosynthetic pathway. This pathway can be rapidly deployed to biosynthesize auxin at the high levels required to initiate the multiple changes in body plan associated with shade avoidance. Experiment Overall Design: Wild type Col-0, sav3-2 and sav1-1 seedlings were used here. They were treated with or without 1hr of low R:FR light (R:FR ratio=0.7). Three independent biological replicates were used.