Organelles Contribute Differentially to Reactive Oxygen Species-Related Events during Extended Darkness      

Abstract

Treatment of Arabidopsis (Arabidopsis thaliana) leaves by extended darkness generates a genetically activated senescence program that culminates in cell death. The transcriptome of leaves subjected to extended darkness was found to contain a variety of reactive oxygen species (ROS)-specific signatures. The levels of transcripts constituting the transcriptome footprints of chloroplasts and cytoplasm ROS stresses decreased in leaves, as early as the second day of darkness. In contrast, an increase was detected in transcripts associated with mitochondrial and peroxisomal ROS stresses. The sequential changes in the redox state of the organelles during darkness were examined by redox-sensitive green fluorescent protein probes (roGFP) that were targeted to specific organelles. In plastids, roGFP showed a decreased level of oxidation as early as the first day of darkness, followed by a gradual increase to starting levels. However, in mitochondria, the level of oxidation of roGFP rapidly increased as early as the first day of darkness, followed by an increase in the peroxisomal level of oxidation of roGFP on the second day. No changes in the probe oxidation were observed in the cytoplasm until the third day. The increase in mitochondrial roGFP degree of oxidation was abolished by sucrose treatment, implying that oxidation is caused by energy deprivation. The dynamic redox state visualized by roGFP probes and the analysis of microarray results are consistent with a scenario in which ROS stresses emanating from the mitochondria and peroxisomes occur early during darkness at a presymptomatic stage and jointly contribute to the senescence program.

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

“…Perturbation of mitochondrial metabolism can result in production of superoxide and H 2 O 2 (Noctor et al, 2007;Miller et al, 2010). It was recently shown that mitochondria and peroxisomes work in a successive manner generating oxidative signals in response to the induction of senescence (Rosenwasser et al, 2011). Consistent with this, it is of interest that mitochondrial mutants of alternative oxidase activity are negatively regulated with many of the stresses (see AS-Aox1 and TDNA-Aox1; Fig.…”

“…The actual maximum correlation value and signal size is assembled in Supplemental Table S1 and ranged from 0.62 for 1 h OG application to a high of 0.85 for 309 flg22 treatment. Such correlation values can be considered highly significant (Volodarsky et al, 2009;Rosenwasser et al, 2011Rosenwasser et al, , 2013 and point to the involvement of a singlet oxygen-like signature in those data sets.…”

“…2A). Note that (Rosenwasser et al, 2011(Rosenwasser et al, , 2013. The source of transcriptome data used for the bioinformatics analysis and abbreviations are in Supplemental Table S10.…”

“…We employed the ROSMETER bioinformatic platform, which compares a test transcriptome by a vector-based correlation method to preselected indices of a recognized ROS type. The indices were generated from various mutants and treatments that produce ROS of a defined type and cellular source (Rosenwasser et al, 2011(Rosenwasser et al, , 2013. Both the direction and strength of the fold induction of each gene were compared and summed over all matching genes in the index to yield a correlation value.…”

Reactive oxygen species and plant resistance to fungal pathogens

“…Finally, it is possible to determine the redox potential of the glutathione pool in a high spatial and temporal resolution using various redox-sensitive green fluorescent proteins (for example roGFP) encoded in the test plant. The method requires transient or permanent plant transformation and has already been used in many cases (Beneloujaephajri et al, 2013;Heller et al, 2012;Jubany-Mari et al, 2010;Lehmann et al, 2009;Rosenwasser et al, 2011).…”