Background: Trapa L. is a floating-leaved aquatic plant with important economic and ecological values. However, the species identification and phylogenetic relationship within Trapa are still controversial, which necessitates the need for plastid genome information of Trapa. In this study, complete chloroplast genomes of 13 Trapa species/taxa were sequenced and annotated. Combined with released sequences, comparative analyses of chloroplast genomes were performed on the 15 Trapa species/taxa for the first time. Results: The Trapa chloroplast genomes exhibited typical quadripartite structures with lengths from 155,453 to 155,559 bp. The gene orders and contents within Trapa were conservative, but several changes were found in the microstructure. The intron loss of rpl2, also detected in Lythraceae, was found in all Trapa species/taxa, suggesting close genetic relationship between Lythraceae and Trapaceae. Notably, two small-seed species (T. incisa and T. maximowiczii) showed the smallest genome size with 155,453 and 155,477 bp, respectively. Each cp genome contained the same 130 genes consisting of 85 protein-coding genes, 37 tRNA genes and 8 rRNA genes. Trapa species/taxa showed 37 (T. incisa and T. maximowiczii) to 41 (T. sibirica) long repeats, including forward, palindromic, reversed and complementary repeats. There were 110 (T. quadrispinosa) to 123 (T. incisa and T. maximowiczii) SSR (simple sequence repeat) loci in Trapa chloroplast genomes. Comparative analyses revealed that two hotspot regions (atpA—atpF and rps2—rpoC2) in Trapa chloroplast genomes could be served as potential molecular markers. Three phylogenetic analyses (ML, MP and BI) consistently showed that there were two clusters within Trapa, including large- and small-seed species/taxa, respectively; for the large-seed Trapa, they clustered according to their geographical origin and tubercle morphology on the surface of seeds. Conclusion: In summary, we have acquired the sequences of 13 Trapa chloroplast genomes, and performed the comparative analyses within Trapa for the first time. The results have helped us better identify the Trapa species/taxa and deepen the understanding of genetic basis and phylogenetic relationship of Trapa, which will facilitate the effective management and utilization of the important genetic resources in the future.

The Yi River, the second longest river in Shandong Province, China, flows through Linyi City and is fed by three tributary rivers, Beng River, Liuqing River, and Su River in the northeastern part of the city. In this study, we determined the concentrations of five heavy metals (Cr, Ni, Cu, Zn, and Pb) in water, sediment, and aquatic macrophyte samples collected from the junction of the four rivers and evaluated the potential ecological risk of heavy metal pollution. Most of the heavy metals in water were in low concentrations with the water quality index (WQI) below 1, suggesting low metal pollution. The sediments showed low heavy metal concentrations, suggesting a low ecological risk based on the potential ecological risk index (RI) and the geo-accumulation index (I_geo). The aquatic plant species Potamogeton crispus accumulated considerable amounts of heavy metals, which were closely related to the metal concentrations of the sediment. The plant species Salvinia natans also showed an excellent metal accumulation capability. Based on our results, the junction of the four rivers is only slightly polluted in terms of heavy metals, and the plant species P. crispus is a suitable bioindicator for sediment heavy metal pollution.

Folic acid is a water-soluble B vitamin, and plays an important role in regulating gene expression and methylation. The liver is the major site of lipid biosynthesis in the chicken. Nevertheless, how gene expression and regulatory networks are affected by folic acid in liver of broilers are poorly understood. This paper conducted the RNA-seq technology on the liver of broilers under folic acid challenge investigation. First, 405 differentially expressed genes (DEGs), including 157 significantly upregulated and 248 downregulated, were detected between the control group (C) and the 5 mg folic acid group (M). Second, 68 upregulated DEGs and 142 downregulated DEGs were determined between C group and 10 mg folic acid group (H). Third, there were 165 upregulated genes and 179 downregulated genes between M and H groups. Of these DEGs, 903 DEGs were successfully annotated in the public databases. The functional classification based on GO and KEEGG showed that “general function prediction only” represented the largest functional classes, “cell cycle” (C vs. M; M vs. H), and “neuroactive ligand-receptor interaction” (C vs. H) were the highest unique sequences among three groups. SNP analysis indicated that numbers of C, M and H groups were 145,450, 146,131, and 123,004, respectively. Total new predicted alternative splicing events in C, M, and H groups were 9,521, 9,328, and 8,929, respectively. A protein-protein interaction (PPI) network was constructed, and the top 10 hub genes were evaluated among three groups. The results of real time PCR indicated that mRNA abundance of PPARγ and FAS in abdominal fat of M and H groups were reduced compared with the C group (P < 0.05). Ultramicroscopy results showed that folic acid could reduce lipid droplets in livers from chickens. Finally, contents of LPL, PPARγ, and FAS in abdominal fat were decreased with the folic acid supplmented diets (P < 0.01). These findings reveal the effects of folic acid supplemention on gene expression in liver of broilers, which can provide information for understanding the molecular mechanisms of folic acid regulating liver lipid metabolism.