Genomic and cytogenetic analyses reveal satellite repeat signature in allotetraploid okra (Abelmoschus esculentus).

BACKGROUND: Satellite repeats are one of the most rapidly evolving components in eukaryotic genomes and play vital roles in genome regulation, genome evolution, and speciation. As a consequence, the composition, abundance and chromosome distribution of satellite repeats often exhibit variability across various species, genome, and even individual chromosomes. However, we know little about the satellite repeat evolution in allopolyploid genomes. RESULTS: In this study, we investigated the satellite repeat signature in five okra (Abelmoschus esculentus) accessions using genomic and cytogenetic methods. In each of the five accessions, we identified eight satellite repeats, which exhibited a significant level of intraspecific conservation. Through fluorescence in situ hybridization (FISH) experiments, we observed that the satellite repeats generated multiple signals and exhibited variations in copy number across chromosomes. Intriguingly, we found that five satellite repeats were interspersed with centromeric retrotransposons, signifying their involvement in centromeric satellite repeat identity. We confirmed subgenome-biased amplification patterns of these satellite repeats through existing genome assemblies or dual-color FISH, indicating their distinct dynamic evolution in the allotetraploid okra subgenome. Moreover, we observed the presence of multiple chromosomes harboring the 35 S rDNA loci, alongside another chromosomal pair carrying the 5 S rDNA loci in okra using FISH assay. Remarkably, the intensity of 35 S rDNA hybridization signals varied among chromosomes, with the signals predominantly localized within regions of relatively weak DAPI staining, associated with GC-rich heterochromatin regions. Finally, we observed a similar localization pattern between 35 S rDNA and three satellite repeats with high GC content and confirmed their origin in the intergenic spacer region of the 35 S rDNA. CONCLUSIONS: Our findings uncover a unique satellite repeat signature in the allotetraploid okra, contributing to our understanding of the composition, abundance, and chromosomal distribution of satellite repeats in allopolyploid genomes, further enriching our understanding of their evolutionary dynamics in complex allopolyploid genomes.

Variation Law of Hybrid Explosion Characteristic Parameters of Gas and Coal Dust Coupled with Multiple Factors.

This study aims at extensively investigating the explosion characteristics of a hybrid mixture of gas and coal dust. Accordingly, the standard 20 L spherical explosion system was applied to measure parameters such as the lower explosion limit, maximum explosion pressure, and index of the hybrid mixture of different concentrations of gas and coal dust. Moreover, different coal dust particle sizes and components were measured. With regard to coal dust with different particle sizes and components, the obtained results revealed that, while the addition of gas significantly reduced the lower explosion limit, the maximum explosion pressure and index were increased; that is to say, the presence of gas will increase the explosion risk of coal dust. However, under conditions in which the particle size of the coal dust was large or the volatile content was low, the addition of gas was found to lead to a higher decrease of the lower explosion limit; this is, while the maximum explosion pressure and explosion index were increased. Consequently, gas can be argued to have a greater influence on the explosion risk of coal dust with a large particle size or low volatile content. Furthermore, regardless of the particle size or the volatile content of coal dust, the maximum explosion pressure and explosion index of the hybrid mixture were observed to be higher than that of the pure coal dust but lower than that of the pure gas. That is to say, the explosion intensity of the gas/coal dust composite system is higher than that of pure coal dust but less than that of pure gas. The research results can provide theoretical basis for coal mine explosion disaster prevention and control and have important significance.

HIV Pre-Exposure Prophylaxis Use on a Global Scale Among Men Who Have Sex with Men: A Systematic Review and Meta-Analysis.

Knowledge of the proportion of Pre-Exposure Prophylaxis (PrEP) use among men who have sex with men (MSM) and the specific gaps in PrEP use can stimulate enhanced focus on HIV prevention policies and programs. To summarize the proportion of PrEP use and explore the temporal trend in the proportion of PrEP use and factors associated with PrEP use among MSM on a global scale, we searched PubMed, Embase, Web of Science Core Collection, and APA PsycINFO for studies reporting on the use of HIV PrEP among MSM before April 2022. Freeman-Tukey double arc-sine transformation and random-effects models were used to pool estimates. A total of 147 articles involving 395,218 MSM were included. The pooled proportions of PrEP use among MSM and PrEP-eligible MSM were 11.23% [95% confidence interval (CI): 9.71-12.84] and 16.04% (95% CI: 11.99-23.36), respectively. The proportion of PrEP use varied among countries with different support policies. ß regressions with the logit link showed that the proportion of PrEP use has increased in recent years. Interrupted time series analyses further supported that the approval of PrEP use would decrease the number of new HIV diagnoses among MSM. The main factors associated with PrEP use include health insurance, having a regular medical provider, prior HIV testing, past use of PrEP or Post-Exposure Prophylaxis, social networks, and stigma. Although the proportion of PrEP use among MSM has remained low, it has increased in recent years. More studies are needed to explore the factors associated with PrEP use, especially for PrEP-eligible MSM in low- and middle-income countries.