Hybridization and divergent climatic preferences drive divergence of two allopatric Gentiana species on the Qinghai-Tibet Plateau.

BACKGROUND AND AIMS: Exploring how species diverge is vital for understanding the drivers of speciation. Factors such as geographical separation and ecological selection, hybridization, polyploidization and shifts in mating system are all major mechanisms of plant speciation, but their contributions to divergence are rarely well understood. Here we test these mechanisms in two plant species, Gentiana lhassica and G. hoae, with the goal of understanding recent allopatric species divergence on the Qinghai-Tibet Plateau (QTP). METHODS: We performed Bayesian clustering, phylogenetic analysis and estimates of hybridization using 561 302 nuclear genomic single nucleotide polymorphisms (SNPs). We performed redundancy analysis, and identified and annotated species-specific SNPs (ssSNPs) to explore the association between climatic preference and genetic divergence. We also estimated genome sizes using flow cytometry to test for overlooked polyploidy. KEY RESULTS: Genomic evidence confirms that G. lhassica and G. hoae are closely related but distinct species, while genome size estimates show divergence occurred without polyploidy. Gentiana hoae has significantly higher average FIS values than G. lhassica. Population clustering based on genomic SNPs shows no signature of recent hybridization, but each species is characterized by a distinct history of hybridization with congeners that has shaped genome-wide variation. Gentiana lhassica has captured the chloroplast and experienced introgression with a divergent gentian species, while G. hoae has experienced recurrent hybridization with related taxa. Species distribution modelling suggested range overlap in the Last Interglacial Period, while redundancy analysis showed that precipitation and temperature are the major climatic differences explaining the separation of the species. The species differ by 2993 ssSNPs, with genome annotation showing missense variants in genes involved in stress resistance. CONCLUSIONS: This study suggests that the distinctiveness of these species on the QTP is driven by a combination of hybridization, geographical isolation, mating system differences and evolution of divergent climatic preferences.

Exposure to 2.45 GHz electromagnetic fields elicits an HSP-related stress response in rat hippocampus.

The issue of possible neurobiological effects of the electromagnetic field (EMF) exposure is highly controversial. To determine whether electromagnetic field exposure could act as an environmental stimulus capable of producing stress responses, we employed the hippocampus, a sensitive target of electromagnetic radiation, to assess the changes in its stress-related gene and protein expression after EMF exposure. Adult male Sprague-Dawley rats with body restrained were exposed to a 2.45 GHz EMF at a specific absorption rate (SAR) of 6 W/kg or sham conditions. cDNA microarray was performed to examine the changes of gene expression involved in the biological effects of electromagnetic radiation. Of 2048 candidate genes, 23 upregulated and 18 downregulated genes were identified. Of these differential expression genes, two heat shock proteins (HSP), HSP27 and HSP70, are notable because expression levels of both proteins are increased in the rat hippocampus. Result from immunocytochemistry revealed that EMF caused intensive staining for HSP27 and HSP70 in the hippocampus, especially in the pyramidal neurons of cornu ammonis 3 (CA3) and granular cells of dentate gyrus (DG). The gene and protein expression profiles of HSP27 and HSP70 were further confirmed by reverse transcription polymerase chain reaction (RT-PCR) and Western blot. Our data provide direct evidence that exposure to electromagnetic fields elicits a stress response in the rat hippocampus.

[Relationship between activation of microglia and Jaks phosphorylation induced by microwave irradiation].

OBJECTIVE: To explore the relationship between microglial proinflammatory and electromagnetic radiation and unveil the role of microglia in microwave radiation induced central nervous system injury. METHODS: N9 microglia cells cultured in vitro were exposed to microwave at 90 mW/cm2. Cell flow cytometry was used to observe the expression of CD11b at different time points after exposure; ELISA was used to detect the concentration of TNF-alpha in N9 cell culture supernatant; RT-PCR analysis confirmed iNOS mRNA expression in N9 microglia cells; and Nitrate Reductase Method was used to test NO amount in culture supernatant. RESULTS: The CD11b positive microglial cells increased significantly at 3 h after microwave exposure (P < 0.05), continued to increase until 24 h and peaked at 6 h after exposure. The amount of TNF-alpha rose dramatically from 1 h to 24 h after exposure (P < 0.01) and peaked at 3 h [(762.1 +/- 61.5) pg/ml] after exposure (P < 0.01). The level of NO started to increase at 1 h [(4.48-0.59) micromol/L] and lasted for 24 h after exposure. The expression of iNOS mRNA increased significantly at 1 h (P < 0.05), and tripled the original expression at 6 h after exposure, hereafter, it decreased slightly, but all were higher than the control group within 24 h after exposure. CONCLUSION: Microwave radiation could induce the activation of microglia cells. The activated microglia cells could induce microglial proinflammatory by producing large amounts of TNF-alpha, NO, etc.

[Effects of occupational microwave irradiation on heat shock protein 70 expressions in rat hippocampus].

OBJECTIVE: To study the change of heat shock protein (HSP)70 expression after exposure to occupational microwave in rats hippocampus, and explore the role of HSP70 in the mechanism of bio-effect of microwave irradiation. METHODS: The animal model was established by whole body exposures in 90, 5 W/cm(2) microwave irradiation field for 20 min in rats. Changes of the mRNA of hsp70 expressions in rat hippocampus at different time were studied by RT-PCR, and the protein change by Western blot. RESULTS: The mRNA and protein expression of hsp70 in rat hippocampus increased after 90 W/cm(2) and 5 W/cm(2) microwave irradiation for 20 min. The anal temperature and the value of SAR increased significantly. These changes were positively correlated with power and irradiation time of microwave. The results indicated that microwave irradiation led to HSP70 syntheses effectively. CONCLUSION: Microwave irradiation can obviously induce the thermal effect and activate HSP70, and initiate the endogenous protective mechanism of central nervous system.