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.
Highlights
Treatment of Arabidopsis (Arabidopsis thaliana) leaves by extended darkness generates a genetically activated senescence program that culminates in cell death
Our interest is in constructing a senescence model for cut leafy crops; we examined throughout this work the seventh rosette leaf of detached rosettes
In order to validate the microarray results, the expression patterns of 12 genes, including SENESCENCE-ASSOCIATED GENE12 (SAG12), WRKY6, and WRKY53, were followed by quantitative reverse transcription (Q-RT)-PCR and compared with the relative fold change predicted by the microarray data
Summary
Treatment of Arabidopsis (Arabidopsis thaliana) leaves by extended darkness generates a genetically activated senescence program that culminates in cell death. 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. 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. Developmental senescence might be triggered by ROS (Miao et al, 2004), which has been suggested as the cause of early death symptoms in the mutant constitutive expression of PR genes5/onset of leaf death, in which ROS-related stress was observed in presymptomatic leaves (Jing et al, 2008). Similar data for dark-induced senescence in normal leaves are lacking
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
