An extensive microarray analysis of AAL-toxin-induced cell death in Arabidopsis thaliana brings new insights into the complexity of programmed cell death in plants

A T-DNA knockout of the Arabidopsis homologue of the tomato disease resistance gene Asc was obtained. The asc gene renders plants sensitive to programmed cell death (PCD) triggered by the fungal AAL toxin. To obtain more insights into the nature of AAL-toxin-induced cell death and to identify genes of potential importance for PCD, we carried out transcription profiling of AAL-toxin-induced cell death in this knockout with an oligonucleotide array representing 21,500 Arabidopsis genes. Genes responsive to reactive oxygen species (ROS) and ethylene were among the earliest to be upregulated, suggesting that an oxidative burst and production of ethylene played a role in the activation of the cell death. This notion was corroborated by induction of several genes encoding ROS-generating proteins, including a respiratory burst oxidase and germin oxalate oxidase. Cytochemical studies confirmed the oxidative burst and, in addition, showed synthesis of callose, a feature of the hypersensitive response. A diverse group of transcription factors was also induced. These events were followed by repression of most of the auxin-regulated genes known to be involved in growth and developmental responses. All photosynthesis-related genes were repressed. Blocking the synthesis of ethylene or NO significantly compromised cell death. In addition, we identified a heterogeneous group of early-induced genes, some of them never before associated with PCD. The group of early-induced genes included a number of proteases that were previously implicated in developmentally regulated types of PCD, suggesting a more principal role for these proteases in the PCD process. These findings provide new insights into the molecular mechanisms of plant PCD

A novel seed plants gene regulates oxidative stress tolerance in arabidopsis thaliana

Oxidative stress can lead to plant growth retardation, yield loss, and death. The atr7 mutant of Arabidopsis thaliana exhibits pronounced tolerance to oxidative stress. Using positional cloning, confirmed by knockout and RNA interference (RNAi) lines, we identified the atr7 mutation and revealed that ATR7 is a previously uncharacterized gene with orthologs in other seed plants but with no homology to genes in lower plants, fungi or animals. Expression of ATR7-GFP fusion shows that ATR7 is a nuclear-localized protein. RNA-seq analysis reveals that transcript levels of genes encoding abiotic- and oxidative stress-related transcription factors (DREB19, HSFA2, ZAT10), chromatin remodelers (CHR34), and unknown or uncharacterized proteins (AT5G59390, AT1G30170, AT1G21520) are elevated in atr7. This indicates that atr7 is primed for an upcoming oxidative stress via pathways involving genes of unknown functions. Collectively, the data reveal ATR7 as a novel seed plants-specific nuclear regulator of oxidative stress response

A novel seed plants gene regulates oxidative stress tolerance in arabidopsis thaliana

Oxidative stress can lead to plant growth retardation, yield loss, and death. The atr7 mutant of Arabidopsis thaliana exhibits pronounced tolerance to oxidative stress. Using positional cloning, confirmed by knockout and RNA interference (RNAi) lines, we identified the atr7 mutation and revealed that ATR7 is a previously uncharacterized gene with orthologs in other seed plants but with no homology to genes in lower plants, fungi or animals. Expression of ATR7-GFP fusion shows that ATR7 is a nuclear-localized protein. RNA-seq analysis reveals that transcript levels of genes encoding abiotic- and oxidative stress-related transcription factors (DREB19, HSFA2, ZAT10), chromatin remodelers (CHR34), and unknown or uncharacterized proteins (AT5G59390, AT1G30170, AT1G21520) are elevated in atr7. This indicates that atr7 is primed for an upcoming oxidative stress via pathways involving genes of unknown functions. Collectively, the data reveal ATR7 as a novel seed plants-specific nuclear regulator of oxidative stress response

A novel seed plants gene regulates oxidative stress tolerance in arabidopsis thaliana

Oxidative stress can lead to plant growth retardation, yield loss, and death. The atr7 mutant of Arabidopsis thaliana exhibits pronounced tolerance to oxidative stress. Using positional cloning, confirmed by knockout and RNA interference (RNAi) lines, we identified the atr7 mutation and revealed that ATR7 is a previously uncharacterized gene with orthologs in other seed plants but with no homology to genes in lower plants, fungi or animals. Expression of ATR7-GFP fusion shows that ATR7 is a nuclear-localized protein. RNA-seq analysis reveals that transcript levels of genes encoding abiotic- and oxidative stress-related transcription factors (DREB19, HSFA2, ZAT10), chromatin remodelers (CHR34), and unknown or uncharacterized proteins (AT5G59390, AT1G30170, AT1G21520) are elevated in atr7. This indicates that atr7 is primed for an upcoming oxidative stress via pathways involving genes of unknown functions. Collectively, the data reveal ATR7 as a novel seed plants-specific nuclear regulator of oxidative stress response

A comparison of quantitative and qualitative superoxide dismutase assays for application to low temperature microalgae

Antioxidant enzymes such as superoxide dismutase (SOD) play a key role in the removal of reactive oxygen species produced during visible and ultraviolet irradiance stress in microalgae and plants. However, little is known about the enzymatic antioxidative stress responses in ecologically important Antarctic marine microalgae. SOD in particular is difficult to analyze, possibly due to problems in obtaining sufficient quantities necessary for reliable and reproducible enzymatic assays. The aim of the present work was to create a sensitive, easy-to-use and reliable method for SOD determination in Antarctic microalgal material by comparing and optimizing existing protein extraction procedures and SOD assays in the marine Antarctic diatom Chaetoceros brevis. Optimization was achieved in cell disruption (sonication) and protein extraction procedures, extraction buffers, SOD assay methods (xanthine/xanthine oxidase and NBT/riboflavin photometric quantitative methods and native gel electrophoresis qualitative method) and the assay temperature. Protein extraction was optimal at low sonication amplitudes after a few pulses, irrespective of the type of buffer used. Extraction efficiency varied highly between the tested buffers; most protein was extracted in the presence of 1% of Triton X-100. SOD activity was best quantified using the NBT/riboflavin method in combination with a buffer containing potassium phosphate and Triton X-100. Moreover, the NBT/riboflavin method was demonstrated to be the most reliable and sensitive method at low temperatures (5 °C).

A novel seed plants gene regulates oxidative stress tolerance in arabidopsis thaliana

Oxidative stress can lead to plant growth retardation, yield loss, and death. The atr7 mutant of Arabidopsis thaliana exhibits pronounced tolerance to oxidative stress. Using positional cloning, confirmed by knockout and RNA interference (RNAi) lines, we identified the atr7 mutation and revealed that ATR7 is a previously uncharacterized gene with orthologs in other seed plants but with no homology to genes in lower plants, fungi or animals. Expression of ATR7-GFP fusion shows that ATR7 is a nuclear-localized protein. RNA-seq analysis reveals that transcript levels of genes encoding abiotic- and oxidative stress-related transcription factors (DREB19, HSFA2, ZAT10), chromatin remodelers (CHR34), and unknown or uncharacterized proteins (AT5G59390, AT1G30170, AT1G21520) are elevated in atr7. This indicates that atr7 is primed for an upcoming oxidative stress via pathways involving genes of unknown functions. Collectively, the data reveal ATR7 as a novel seed plants-specific nuclear regulator of oxidative stress response