Singlet Oxygen Signatures Are Detected Independent of Light or Chloroplasts in Response to Multiple Stresses    

Abstract

The production of singlet oxygen is typically associated with inefficient dissipation of photosynthetic energy or can arise from light reactions as a result of accumulation of chlorophyll precursors as observed in fluorescent (flu)-like mutants. Such photodynamic production of singlet oxygen is thought to be involved in stress signaling and programmed cell death. Here we show that transcriptomes of multiple stresses, whether from light or dark treatments, were correlated with the transcriptome of the flu mutant. A core gene set of 118 genes, common to singlet oxygen, biotic and abiotic stresses was defined and confirmed to be activated photodynamically by the photosensitizer Rose Bengal. In addition, induction of the core gene set by abiotic and biotic selected stresses was shown to occur in the dark and in nonphotosynthetic tissue. Furthermore, when subjected to various biotic and abiotic stresses in the dark, the singlet oxygen-specific probe Singlet Oxygen Sensor Green detected rapid production of singlet oxygen in the Arabidopsis (Arabidopsis thaliana) root. Subcellular localization of Singlet Oxygen Sensor Green fluorescence showed its accumulation in mitochondria, peroxisomes, and the nucleus, suggesting several compartments as the possible origins or targets for singlet oxygen. Collectively, the results show that singlet oxygen can be produced by multiple stress pathways and can emanate from compartments other than the chloroplast in a light-independent manner. The results imply that the role of singlet oxygen in plant stress regulation and response is more ubiquitous than previously thought.

The ROS Wheel: Refining ROS Transcriptional Footprints

“…6C). Thus, our analysis here reveals transcriptional footprints that are consistent with previously conducted stress analyses (Hahn et al, 2013) or ROS-inspired meta-analysis (Gadjev et al, 2006;Mor et al, 2014).…”

“…6B; Hahn et al, 2013) and supports the 1 O 2 -responsive gene set found in early stress responses ( Fig. 6C; Mor et al, 2014). Footprints associated with specific (subcellular) types of ROS probably exist, although they do not seem to be major discernible factors among diverse studies, except the early 1 O 2 footprint of cluster VI.…”

“…The footprint of cluster VI had 24 PCESR genes in common, suggesting early 1 O 2 signaling as an important factor in the environmental stress response. The presence of 1 O 2 transcriptome footprints in biotic and abiotic stresses was observed previously (Mor et al, 2014). Mor et al (2014) determined a 1 O 2 -responsive set of 118 core genes by filtering genes differentially expressed in nine out of 12 microarray experiments after 10 min to 1 h of stress.…”

“…The presence of 1 O 2 transcriptome footprints in biotic and abiotic stresses was observed previously (Mor et al, 2014). Mor et al (2014) determined a 1 O 2 -responsive set of 118 core genes by filtering genes differentially expressed in nine out of 12 microarray experiments after 10 min to 1 h of stress. The footprints of clusters V and VI reported in total 95% of this 1 O 2 core gene set (Fig.…”

“…Previous comparative studies assessed the relative contribution to changes in gene expression provoked by specific types of ROS, such as H 2 O 2 or singlet oxygen ( 1 O 2 ), and/or by their accumulation in a particular subcellular compartment (Laloi et al, 2007;Sewelam et al, 2014), and demonstrated various ROS transcriptional footprints during developmental processes and abiotic and biotic stress conditions (Lai et al, 2012;Rosenwasser et al, 2013;Mor et al, 2014). To facilitate recognition of ROS transcriptional footprints, a vectorbased algorithm, designated ROSMETER was developed (Rosenwasser et al, 2013).…”