Presentation8_Plant competition cues activate a singlet oxygen signaling pathway in Arabidopsis thaliana.pptx

<p>Oxidative stress responses of Arabidopsis to reflected low red to far-red signals (R:FR ≈ 0.3) generated by neighboring weeds or an artificial source of FR light were compared with a weed-free control (R:FR ≈1.6). In the low R:FR treatments, induction of the shade avoidance responses (SAR) coincided with increased leaf production of singlet oxygen (<sup>1</sup>O<sub>2</sub>). This <sup>1</sup>O<sub>2</sub> increase was not due to protochlorophyllide accumulation and did not cause cell death. Chemical treatments, however, with 5-aminolevulinic acid (the precursor of tetrapyrrole biosynthesis) and glutathione (a quinone A reductant) enhanced cell death and growth inhibition. RNA sequencing revealed that transcriptome responses to the reflected low R:FR light treatments minimally resembled previously known Arabidopsis<sup>1</sup>O<sub>2</sub> generating systems that rapidly generate <sup>1</sup>O<sub>2</sub> following a dark to light transfer. The upregulation of only a few early <sup>1</sup>O<sub>2</sub> responsive genes (6 out of 1931) in the reflected low R:FR treatments suggested specificity of the <sup>1</sup>O<sub>2</sub> signaling. Moreover, increased expression of two enzyme genes, the SULFOTRANSFERASE ST2A (ST2a) and the early <sup>1</sup>O<sub>2</sub>-responsive IAA-LEUCINE RESISTANCE (ILR)-LIKE6 (ILL6), which negatively regulate jasmonate level, suggested that repression of bioactive JAs may promote the shade avoidance (versus defense) and <sup>1</sup>O<sub>2</sub> acclimation (versus cell death) responses to neighboring weeds.</p>