Identification and Characterization of SOG1 (Suppressor of Gamma Response 1) Homologues in Plants Using Data Mining Resources and Gene Expression Profiling

MicroRNAs potentially targeting DDR-related genes are differentially expressed upon exposure to γ-rays during seed germination in wheat

DNA damage response (DDR), a complex network of cellular pathways that cooperate to sense and repair DNA lesions, is regulated by several mechanisms, including microRNAs. As small, single-stranded RNA molecules, miRNAs post-transcriptionally regulate their target genes by mRNA cleavage or translation inhibition. Knowledge regarding miRNAs influence on DDR-associated genes is still scanty in plants. In this work, an in silico analysis was performed to identify putative miRNAs that could target DDR sensors, signal transducers and effector genes in wheat. Selected putative miRNA-gene pairs were tested in an experimental system where seeds from two wheat mutant lines were irradiated with 50 Gy and 300 Gy gamma(γ)-rays. To evaluate the effect of the treatments on wheat germination, phenotypic and molecular (DNA damage, ROS accumulation, gene/miRNA expression profile) analyses have been carried out. The results showed that in dry seeds ROS accumulated immediately after irradiation and decayed soon after while the negative impact on seedling growth was supported by enhanced accumulation of DNA damage. When a qRT-PCR analysis was performed, the selected miRNAs and DDR-related genes were differentially modulated by the γ-rays treatments in a dose-, time- and genotype-dependent manner. A significant negative correlation was observed between the expression of tae-miR5086 and the RAD50 gene, involved in double-strand break sensing and homologous recombination repair, one of the main processes that repairs DNA breaks induced by γ-rays. The results hereby reported can be relevant for wheat breeding programs and screening of the radiation response and tolerance of novel wheat varieties.

Comparing cadmium-induced effects on the regulation of the DNA damage response and cell cycle progression between entire rosettes and individual leaves of Arabidopsis thaliana

Cadmium (Cd) activates the DNA damage response (DDR) and inhibits the cell cycle in Arabidopsis thaliana through the transcription factor SUPPRESSOR OF GAMMA RESPONSE 1. The aim of this study was to investigate which individual leaf best reflects the Cd-induced effects on the regulation of the DDR and cell cycle progression in rosettes, enabling a more profound interpretation of the rosette data since detailed information, provided by the individual leaf responses, is lost when studying the whole rosette. Wild-type A. thaliana plants were cultivated in hydroponics and exposed to different Cd concentrations. Studied individual leaves were leaf 1 and 2, which emerged before Cd exposure, and leaf 3, which emerged upon Cd exposure. The DDR and cell cycle regulation were studied in rosettes as well as individual leaves after several days of Cd exposure. Varying concentration-dependent response patterns were observed between the entire rosette and individual leaves. Gene expression of selected DDR and cell cycle regulators showed higher similarity in their response between the rosette and the individual leaf emerged during Cd exposure than between both individual leaves. The same pattern was observed for plant growth and cell cycle-related parameters. We conclude that Cd-induced effects on the regulation of the DDR and cell cycle progression in the leaf that emerged during Cd exposure, resemble those observed in the rosette the most, which contributes to the interpretation of the rosette data in the framework of plant development and after exposure to Cd.

Engineered gamma radiation phytosensors for environmental monitoring

Nuclear energy, already a practical solution for supplying energy on a scale similar to fossil fuels, will likely increase its footprint over the next several decades to meet current climate goals. Gamma radiation is produced during fission in existing nuclear reactors and thus the need to detect leakage from nuclear plants, and effects of such leakage on ecosystems will likely also increase. At present, gamma radiation is detected using mechanical sensors that have several drawbacks, including: (i) limited availability; (ii) reliance on power supply; and (iii) requirement of human presence in dangerous areas. To overcome these limitations, we have developed a plant biosensor (phytosensor) to detect low-dose ionizing radiation. The system utilizes synthetic biology to engineer a dosimetric switch into potato utilizing the plant's native DNA damage response (DDR) machinery to produce a fluorescent output. In this work, the radiation phytosensor was shown to respond to a wide range of gamma radiation exposure (10-80 Grey) producing a reporter signal that was detectable at >3 m. Further, a pressure test of the top radiation phytosensor in a complex mesocosm demonstrated full function of the system in a 'real world' scenario.

In silico scanning of structural and functional deleterious nsSNPs in Arabidopsis thaliana's SOG1 protein, using molecular dynamic simulation approaches

Suppressor of gamma response 1 (SOG1) is a member of the NAC domain family transcription factors of the DNA damage response (DDR) signaling in the plant's genome. SOG1 is directly involved in transcriptional response to DNA damage, cell cycle checkpoints and ATR or ATM-mediated activation of the DNA damage responses and repair functioning in programmed cell death and regulation of end reduplication. Different mutations in the SOG1 protein lead to severe diseases and, ultimately, cell death. Single nucleotide polymorphisms (SNPs) are an important type of genetic alteration that cause different diseases or programmed cell death. The current study applied different computational approaches to Arabidopsis thaliana L. SOG1 protein to identify the potential deleterious nsSNPs and monitor their impact on the structure, function and protein stability. Various bioinformatics tools were applied to analyze the retrieved 34 nsSNPs and interestingly extracted four deleterious nsSNPs, that is, ensvath13968004 (Q166L), tmp18998388 (P159L), ensvath01103049 (K199N) and tmp18998295 (Y190F). For example, homology modeling, conservation and conformational analysis of the mutant's models were considered to scrutinize the deviations of these variants from the native SOG1 structure. All atoms molecular dynamic simulation confirmed the significance of these mutations on the protein stability, residual and structural conformation, compactness, surface conformation, dominant motion, Gibbs free energy distribution and dynamic effects. Similarly, protein-protein interaction revealed that SOG1 operates as a hub-linking cluster of various proteins, and any changes in the SOG1 might result in the disassociation of several signal transduction cascades.Communicated by Ramaswamy H. Sarma.