Morphological and Transcriptomic Analyses Reveal the Toxicological Mechanism and Risk of Nitrate Exposure in Bufo gargarizans Embryos.

In recent years, nitrate (NO3-N) pollution in water bodies has been increasing due to the excessive use of nitrogen-based fertilizers. Exposure to NO3-N during the development of amphibian embryos may have lasting effects on the growth and development of individuals and even threaten their survival, but the toxicity mechanism of NO3-N in amphibian embryos prior to thyroid morphogenesis remains unclear. In the present study, Bufo gargarizans was selected as the model organism to investigate the toxic effects of 10 mg/L and 100 mg/L NO3-N exposure (N10 and N100) on amphibian embryos using methimazole (MMI) and exogenous thyroxine (T4) as the reference groups. We found that T4, MMI, N10 and N100 inhibited B. gargarizans embryo growth and development, with MMI and N100 showing the earliest and strongest effects. Transcriptome analysis revealed that MMI and NO3-N (especially N100) significantly downregulated genes related to thyroid morphogenesis and cholesterol metabolism, while upregulating genes related to inflammation and apoptosis. Together, these results contribute to a deeper understanding of the complex mechanisms by which NO3-N disrupts B. gargarizans embryonic development, reveal the potential risks of NO3-N pollution to other aquatic organisms, and provide insights into the conservation of a broader ecosystem.

Heterologous expression of rice OsEXO70FX1 confers tolerance to cadmium in Arabidopsis thaliana and fission yeast.

Cadmium (Cd) is an environmental toxicant that accumulates in grains, which greatly increases the risk of human exposure to Cd via food chain. The exocytosis of Cd is one of the essential detoxification mechanisms in plants. OsEXO70s, which facilitate the fusion of secretory vesicles and target membranes, has undergone significant expansion in rice. Here, we uncovered 40 OsEXO70 genes characterized by genome-wide profiling and focused on the potential functions of OsEXO70s, especially OsEXO70FX1, in Cd stress. Overexpression of OsEXO70FX1 enhanced both diamide and Cd tolerances in Schizosaccharomyces pombe (S. pombe), and in Arabidopsis resulted in 11% more seedlings survival rate and about 70% longer primary roots under Cd treatment compared with WT (empty vector). Meanwhile, Cd treatment upregulated the expression levels of some exocyst subunits in overexpression lines. Trichomes isolated from overexpression lines were observed to accumulate more Cd. Also, reactive oxygen species (ROS) induced by Cd stress reflected less sensitivity of OsEXO70FX1 overexpression lines to Cd stress, which was evidenced in the Cd determination assay. These results provide the fundament to future research on rice EXO70 family and suggest that it may have evolved a specialized role in response to Cd stress.

Deep decoding of codon usage strategies and host adaption preferences of soybean mosaic virus.

Soybean mosaic virus (SMV) has threatened the global yield of Leguminosae crops, but the mechanism of its infection, spread, and evolution remains unknown. A systemic analysis of 107 SMV strains was performed to explore the genome-wide codon usage profile and the various factors influencing the codon usage patterns of SMV, which provides insight into its molecular evolution and elucidates its unknown host adaptation pattern. The overall nucleotide composition and correlation analysis revealed that the preferred synonymous codons mostly end with A/U. Clustering by RSCU value of each strain and phylogenetic tree analysis showed that the SMV isolates studied were divided into four clades, with a low overall extent of codon usage bias (CUB) in SMV. According to the ENC, PR2, neutrality plot, and correspondence analysis, natural selection of geographical diversity may play a critical role in the CUB. Higher adaptability was shown in Glycine with SMV and more pressure was received by clade III. These findings could not only provide valuable information about the overall codon usage pattern of the SMV genome, but could also aid in the clarification of the involved mechanisms that dominate the codon usage patterns and genetic evolution of the SMV genome.

Arabidopsis OXS3 family proteins repress ABA signaling through interactions with AFP1 in the regulation of ABI4 expression.

Abscisic acid (ABA) and the AP2/ERF (APETALA2/ETHYLENE-RESPONSIVE FACTOR)-type transcription factor called ABA INSENSITIVE 4 (ABI4) play pivotal roles in plant growth responses to environmental stress. An analysis of seedling development in Arabidopsis ABA hypersensitive mutants suggested that OXS3 (OXIDATIVE STRESS 3), OXS3b, O3L3 (OXS3 LIKE 3), O3L4, and O3L6 were negative regulators of ABI4 expression. We therefore characterized the roles of the OXS3 family members in ABA signaling. All the above five OXS3 proteins were found to interact with AFP1 (ABI FIVE BINDING PROTEIN 1) in yeast two hybrid assays. Seven OXS3 family members including two other members O3L1 and O3L5 were found to interact with histone H2A.X, although OXS3b, O3L3, and O3L5 showed weaker interactions. ChIP-qPCR analysis showed that the absence of some of these OXS3 family proteins was associated with increased occupancy of histone γ-H2A.X at the ABI4 promoter, which also corresponded with de-repression of ABI4 expression. Repression of ABI4 expression, however, required both AFP1 and OXS3, OXS3b or O3L6. We conclude that in the absence of stress, OXS3 family proteins regulate γ-H2A.X deposition at the ABI4 promoter and that together with AFP1, OXS3 family proteins function to prevent ABA-induced growth arrest by co-repressing ABI4 through decreased promoter occupancy of histone γ-H2A.X.

SnRK1 regulates chromatin-associated OXS3 family proteins localization through phosphorylation in Arabidopsis thaliana.

In plants, SNF1-related protein kinase 1 (SnRK1) senses nutrient and energy status and transduces this information into appropriate responses. Oxidative Stress 3 (OXS3) and family members share a highly conserved putative N-acetyltransferase catalytic domain (ACD). Here, we describe that the ACD contains two candidate SnRK1 recognition motifs and that SnRK1 can interact with most of the OXS3 family proteins. In vitro, SnRK1.1 can phosphorylate OXS3, OXS3b and O3L4, and in vivo promote the translocation of OXS3, OXS3b and O3L6 from the nucleus to the cytoplasm. Phosphorylation sites within the OXS3 ACD affect OXS3 cytoplasmic accumulation, as well as their interactions with SnRK1.1. This suggests that signal transduction from SnRK1 to OXS3 family proteins, and that SnRK1 can control their activities through phosphorylation-induced nuclear exclusion.

OXIDATIVE STRESS 3 regulates drought-induced flowering through APETALA 1.

Stress-induced regulation of flowering time insures evolutionary fitness. Stress-induced late flowering is thought to result from a plant evoking tolerance mechanism to wait out the stress before initiating reproduction. Stress-induced early flowering, on the other hand, is thought to be a stress-escape response. By shortening their life cycle to produce seeds before severe stress leads to death, this insures survival of the species at the cost of lower seed yield. Previously, we reported that overexpression of OXS3 (OXIDATIVE STRESS 3) could enhance tolerance to cadmium and oxidizing agents in Arabidopsis whereas an oxs3 null mutant was slightly more sensitive to these chemicals. In this study, we found that the absence of OXS3 also causes early flowering under a mild drought stress treatment. This contrasts with the behavior of wild type Ws4 and Col ecotypes that responded to the same condition by delaying flowering time. We tested the hypothesis that OXS3 might ordinarily exert a negative regulatory role on flowering during drought stress, which in its absence, would lead to stress-induced early flowering. In a search of whether OXS3 could interfere with regulators that activate flowering, we found that OXS3 could bind SOC1 in vitro and in vivo. Overexpression of OXS3 in a transient expression assay was found to repress the AP1 promoter, and the full repression effect required SOC1. It is possible that the OXS3/SOC1 interaction serves to prevent precocious flower development and prevent low seed set from a premature stress-induced flowering response.

New method for retrospective study of hemodynamic changes before and after aneurysm formation in patients with ruptured or unruptured aneurysms.

BACKGROUND: Prospective observation of hemodynamic changes before and after formation of brain aneurysms is often difficult. We used a vessel surface repair method to carry out a retrospective hemodynamic study before and after aneurysm formation in a ruptured aneurysm of the posterior communicating artery (RPcomAA) and an unruptured aneurysm of the posterior communicating artery (URPcomAA). METHODS: Arterial geometries obtained from three-dimensional digital subtraction angiography of cerebral angiograms were used for flow simulation by employing finite-volume modeling. Hemodynamic parameters such as wall shear stress (WSS), blood-flow velocity, streamlines, pressure, and wall shear stress gradient (WSSG) in the aneurysm sac and at the site of aneurysm formation were analyzed in each model. RESULTS: At "aneurysm" status, hemodynamic analyses at the neck, body, and dome of the aneurysm revealed the distal aneurysm neck to be subjected to the highest WSS and blood-flow velocity, whereas the aneurysm dome presented the lowest WSS and blood-flow velocity in both model types. More apparent changes in WSSG at the aneurysm dome with an inflow jet and narrowed impaction zone were revealed only in the RPcomAA. At "pre-aneurysm" status, hemodynamic analyses in both models showed that the region of aneurysm formation was subjected to extremely elevated WSS, WSSG, and blood-flow velocity. CONCLUSIONS: These data suggest that hemodynamic analyses in patients with ruptured or unruptured aneurysms using the vessel surface repair method are feasible, economical, and simple. Our preliminary results indicated that the arterial wall was subjected to elevated WSS, WSSG and blood-flow velocity before aneurysm generation. However, more complicated flow patterns (often with an inflow jet or narrowed impaction zone) were more likely to be observed in ruptured aneurysm.