Effects of polystyrene microplastics acute exposure in the liver of swordtail fish (Xiphophorus helleri) revealed by LC-MS metabolomics.

As global pollution, microplastics pollution has aroused growing concerns. In our experiment, the effect of microplastics acute exposure on the liver of swordtail fish was investigated by using LC-MS metabolomics. Fishes treated with high concentration polystyrene microspheres (1 µm) for 72 h were divided into three concentration groups: (A) no microplastics, (B): 1 × 106 microspheres L-1, (C): 1 × 107 microspheres L-1. Metabolomic analysis indicated that exposure to microplastics caused alterations of metabolic profiles in swordtail fish, including 37 differential metabolites were identified in B vs. A, screened out ten significant metabolites, which involved 14 metabolic pathways. One hundred three differential metabolites were identified in C vs. A, screened out 16 significant metabolites, which involved 30 metabolic pathways. Six significant metabolites were overlapping in group B vs. A and C vs. A; they are 3-hydroxyanthranilic acid, l-histidine, citrulline, linoleic acid, pantothenate, and xanthine. In addition, four metabolic pathways are overlapping in group B vs. A and C vs. A; they are beta-alanine metabolism, biosynthesis of amino acids, linoleic acid metabolism, and aminoacyl-tRNA biosynthesis. These differential metabolites were involved in oxidative stress, immune function, energy metabolism, sugar metabolism, lipid metabolism, molecule transport, and weakened feed utilization, growth performance, nutrient metabolism, and animal growth. Furthermore, we found that the number of interfered amino acids and microplastics showed a dose-effect. In summary, great attention should be paid to the potential impact of microplastics on aquatic organisms.

The Effect of Transitioning between Feeding Methods on the Gut Microbiota Dynamics of Yaks on the Qinghai-Tibet Plateau.

Here we aimed to explore the change in yak gut microbiota after transferring yaks from grazing grassland to a feedlot, and determine their diet adaptation period. Five yaks were transferred from winter pasture to an indoor feedlot. Fecal samples were obtained from grazing (G) and feedlot feeding yaks at day 1 (D1), day 4 (D4), day 7 (D7), day 11 (D11), and day 16 (D16). The dynamic variation of the bacterial community was analyzed using 16S rRNA gene sequencing. The results showed that the yak gut microbial community structure underwent significant changes after diet transition. At the phylum and genus levels, most bacteria changed within D1-D11; however, no significant changes were observed from D11-D16. Furthermore, we used random forest to determine the key bacteria (at class level) disturbing gut micro-ecology. The relative abundance of the top four classes (Erysipelotrichia, Gammaproteobacteria, Saccharimonadia, and Coriobacteriia) was highest on D1-D4, and then decreased and plateaued over time. Our results demonstrated that an abrupt adjustment to a diet with high nutrition could influence the gut micro-ecology, which was stabilized within 16 days, thus providing insights into diet adaptation in the yak gut.

Activation of potassium released from soil by root-secreted organic acids in different varieties of tobacco (Nicotiana tabacum).

Organic acids secreted from the roots of plants play important roles in nutrient acquisition and metal detoxification; however, the precise underlying mechanisms of these processes remain poorly understood. In the present study we examined the content of organic acids exuded from roots and the effects of these organic acids on the activation of slowly available potassium (K) at different K levels, including normal K supply and K-deficient conditions. In addition, the study system also comprised a high-K tobacco variety (ND202) and two common ones (K326 and NC89). Our results showed that high-K varieties exhibited significantly higher contents of organic acids in its root exudates and available K in both rhizosphere and non-rhizosphere soils than the other varieties. This research also suggested that a cyclic process in which soil was acidified after being complexed by organic acids was involved in the release of slowly available K, and that this process primarily depended on the soil pH at high organic acids concentrations, but the complexation of organic ligands became dominant at low concentrations. In conclusion, tobacco roots secrete organic acids to increase available K content and improve the utilisation rate of soil K. High-K varieties probably enhance slowly available K activation by secreting relatively high amounts of organic acids, thus leading to more available K in soil for absorption by plants.

[Difference of potassium absorption characters and mechanism of tobacco in genotypes].

Tabacco (Nicotiana tabacum) has a relatively high requirement for potassium (K). The difference in root characteristics and ability to release K from minerals of flue-cured tobacco in four genotypes ND202, NC628, G28 and NC628 x ND202 were analyzed. The results showed that the more available K released from minerals by roots, the more K would be accumulated by plants. ND202, which was K-enriched genotype, had well developed root system and was easily influenced by K content in the environment. Compared with ND202, NC628 significantly enhanced the effectiveness of K in substrate by releasing K from minerals, though the ability to absorb K was weak. Moreover, the hybrid of NC628 x ND202 had a higher ability to release K and to tolerate low-level K than maternal parent. It was higher in dry matter accumulation and K enrichment than male parent. So hybridization had the utility value in high-K variety cultivation. These results provided evidence that parents should have the ability to enhance available K from soil besides the high combining ability for breeding the high-K variety.

Effect of ploidy increase on transgene expression: example from Citrus diploid cybrid and allotetraploid somatic hybrid expressing the EGFP gene.

Polyploidization is an important speciation mechanism for all eukaryotes, and it has profound impacts on biodiversity dynamics and ecosystem functioning. Green fluorescent protein (GFP) has been used as an effective marker to visually screen somatic hybrids at an early stage in protoplast fusion. We have previously reported that the intensity of GFP fluorescence of regenerated embryoids was also an early indicator of ploidy level. However, little is known concerning the effects of ploidy increase on the GFP expression in citrus somatic hybrids at the plant level. Herein, allotetraploid and diploid cybrid plants with enhanced GFP (EGFP) expression were regenerated from the fusion of embryogenic callus protoplasts from 'Murcott' tangor (Citrus reticulata Blanco × Citrus sinensis (L.) Osbeck) and mesophyll protoplasts from transgenic 'Valencia' orange (C. sinensis (L.) Osbeck) expressing the EGFP gene, via electrofusion. Subsequent simple sequence repeat (SSR), chloroplast simple sequence repeat and cleaved amplified polymorphic sequence analysis revealed that the two regenerated tetraploid plants were true allotetraploid somatic hybrids possessing nuclear genomic DNA of both parents and cytoplasmic DNA from the callus parent, while the five regenerated diploid plants were cybrids containing nuclear DNA of the leaf parent and with complex segregation of cytoplasmic DNA. Furthermore, EGFP expression was compared in cells and protoplasts from mature leaves of these diploid cybrids and allotetraploid somatic hybrids. Results showed that the intensity of GFP fluorescence per cell or protoplast in diploid was generally brighter than in allotetraploid. Moreover, same hybridization signal was detected on allotetraploid and diploid plants by Southern blot analysis. By real-time RT-PCR and Western blot analysis, GFP expression level of the diploid cybrid was revealed significantly higher than that of the allotetraploid somatic hybrid. These results suggest that ploidy level conversion can affect transgene expression and citrus diploid cybrid and allotetraploid somatic hybrid represents another example of gene regulation coupled to ploidy.