Ureides are similarly accumulated in response to UV-C irradiation and wound but differently remobilized during recovery in Arabidopsis leaves

To examine a role of purine degraded metabolites in response to wounding or UV-C stress, the Arabidopsis wild-type (WT) and Atxdh1 KO mutants, defective in xanthine dehydrogenase1 (XDH1), were exposed to wounding and UV-C irradiation stress. In Atxdh1 mutant, wounding or UV-C stresses resulted in lower fresh-weight, increased senescence symptoms and higher tissue cell death rate compared to WT plants. Additionally, WT plants exhibited lower levels of oxidative stress indicators; reactive oxygen species and malondialdehyde than Atxdh1 mutant leaves. Notably, Transcripts and Proteins functioning in purine degradation pathway were orchestrated to lead to enhanced ureide levels in WT leaves 24 h after applying UV-C or wound stress. Yet, different remobilization of the accumulated ureides was noticed 72 h after stresses application. In plants treated with UV-C the allantoin level was highest in young leaves, whereas in wounded plants it was lowest in the young leaves, accumulated mainly in the middle and wounded leaves. The results indicate that in UV-C treated WT plants, during the recovery period from stress, ureides are remobilized from the lower older leaves to support young leaf growth. In contrast, after wounding, the ureides are remobilized to the young leaves, yet more to the middle wounded leaves, to function as antioxidants and/or healing agents.

Ureides are similarly accumulated in response to UV-C irradiation and wound but differently remobilized during recovery in Arabidopsis leaves.

To examine a role of purine degraded metabolites in response to wounding or UV-C stress, the Arabidopsis wild-type and Atxdh1 KO mutants, defective in xanthine dehydrogenase1 (XDH1), were exposed to wounding and UV-C irradiation stress. In Atxdh1 mutant, wounding or UV-C stresses resulted in lower fresh-weight, increased senescence symptoms and higher tissue cell death rate compared to Wild-type. Additionally, Wild-type exhibited lower levels of oxidative stress indicators; reactive oxygen species and malondialdehyde than Atxdh1 mutant leaves. Notably, purine degradation transcripts and proteins were orchestrated to lead to enhanced ureide levels in Wild-type leaves 24 h after applying UV-C or wound stress. Yet, different remobilization of the accumulated ureides was noticed 72 h after stresses application. In plants treated with UV-C the allantoin level was highest in young leaves, whereas in wounded plants it was lowest in the young leaves, accumulated mainly in the middle and wounded leaves. The results indicate that in UV-C treated Wild-type, during the recovery period from stress, ureides are remobilized from the lower older leaves to support young leaf growth. In contrast, after wounding, the ureides are remobilized to the young leaves, yet more to the middle wounded leaves, to function as antioxidants and/or healing agents.

Proteomic Analysis of Vesicle-Producing Pseudomonas aeruginosa PAO1 Exposed to X-Ray Irradiation

Ionizing irradiation kills pathogens by destroying nucleic acids without protein structure destruction. However, how pathogens respond to irradiation stress has not yet been fully elucidated. Here, we observed that Pseudomonas aeruginosa PAO1 could release nucleic acids into the extracellular environment under X-ray irradiation. Using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), X-ray irradiation was observed to induce outer membrane vesicle (OMV) formation in P. aeruginosa PAO1. The size distribution of the OMVs of the irradiated PAO1 was similar to that of the OMVs of the non-irradiated PAO1 according to nanoparticle tracking analysis (NTA). The pyocin-related proteins are involved in OMV production in P. aeruginosa PAO1 under X-ray irradiation conditions, and that this is regulated by the key SOS gene recA. The OMV production was significantly impaired in the irradiated PAO1 Δlys mutant, suggesting that Lys endolysin is associated with OMV production in P. aeruginosa PAO1 upon irradiation stress. Meanwhile, no significant difference in OMV production was observed between PAO1 lacking the pqsR, lasR, or rhlR genes and the parent strain, demonstrating that the irradiation-induced OMV biosynthesis of P. aeruginosa was independent of the Pseudomonas quinolone signal (PQS).

Molecular Characterization and Identification of Calnexin 1 As a Radiation Biomarker from Tradescantia BNL4430

Calnexin (CNX) is an integral membrane protein that functions as a chaperone in the endoplasmic reticulum for the correct folding of proteins under stress conditions, rendering organisms tolerant under adverse conditions. Studies have investigated the cytogenetic effects of gamma irradiation (Ɣ-IR) on plants, but information on the molecular response under Ɣ-IR remains limited. Previously, we constructed a cDNA library of an irradiation-sensitive bioindicator plant, Tradescantia BNL4430 (T-4430) under Ɣ-IR, in which the Calnexin-1 gene was highly upregulated at 50 mGy treatment. TrCNX1 encodes a 61.4 kDa protein with conserved signature motifs similar to already reported CNX1s. TrCNX1 expression was evaluated by semiquantitative reverse transcriptase PCR and quantitative real-time PCR and was ubiquitously expressed in various tissues and highly upregulated in flower petals under 50 mGy Ɣ-IR stress. The protective function of TrCNX1 was investigated by overexpression of TrCNX1 in an Escherichia coli BL21(DE3) heterologous system. Using plate assay, we showed that TrCNX1 increased the viability of E. coli transformants under both UV-B and Ɣ-IR compared with the control, demonstrating that TrCNX1 functions under irradiation stress. TrCNX1 may enhance irradiation stress tolerance in crops and act as a radio marker gene to monitor the effects of radiation.

Radioprotective role of cyanobacterial phycobilisomes

It is now generally accepted that cyanobacteria are responsible for production of oxygen, which led to the so-called “Great Oxygenation Event”. Appearance of dioxygen in Earth’s atmosphere resulted in formation of the ozone layer and the ionosphere, which caused significant reduction of ionizing radiation levels at the surface of our planet. This event not only increased biological diversity but also canceled the urgency of previously developed mechanisms of DNA protection, which allowed to survive and develop in harsh environmental conditions including exposure to cosmic rays. In order to test the hypothesis if one of the oldest organisms on Earth retained ancient protection mechanisms, we studied the effect of ionizing radiation (IoR, here: α-particles with a kinetic energy of about 30 MeV) and space flight during the mission of the Foton-M4 satellite on cells of Synechocystis sp. PCC6803. By analyzing spectral and functional characteristics of photosynthetic membranes we revealed numerous similarities between cells exposed to IoR and after the space mission. In both cases, we found that excitation energy transfer from phycobilisomes to photosystems was interrupted and the concentration of phycobiliproteins was significantly reduced. Although photosynthetic activity was severely suppressed, the effect was reversible and the cells were able to rapidly recover from stress under normal conditions. Moreover, in vitro experiments demonstrated that the effect of IoR on isolated phycobilisomes was completely different from such in vivo. These observations suggest that the actual existence and the uncoupling of phycobilisomes under irradiation stress could play specific role not only in photo-, but also in radioprotection, which was crucial for early stages of evolution and the development of Life on Earth.