Assembly and analysis of the complete mitochondrial genome of Forsythia suspensa (Thunb.) Vahl.

BACKGROUND: Forsythia suspensa (Thunb.) Vahl is a valuable ornamental and medicinal plant. Although the nuclear and chloroplast genomes of F. suspensa have been published, its complete mitochondrial genome sequence has yet to be reported. In this study, the genomic DNA of F. suspensa yellowish leaf material was extracted, sequenced by using a mixture of Illumina Novaseq6000 short reads and Oxford Nanopore PromethION long reads, and the sequencing data were assembled and annotated. RESULT: The F. suspensa mitochondrial genome was obtained in the length of 535,692 bp with a circular structure, and the GC content was 44.90%. The genome contains 60 genes, including 36 protein-coding genes, 21 tRNA genes, and three rRNA genes. We further analyzed RNA editing of the protein-coding genes, relative synonymous codon usage, and sequence repeats based on the genomic data. There were 25 homologous sequences between F. suspensa mitochondria and chloroplast genome, which involved the transfer of 8 mitochondrial genes, and 9473 homologous sequences between mitochondrial and nuclear genomes. Analysis of the nucleic acid substitution rate, nucleic acid diversity, and collinearity of protein-coding genes of the F. suspensa mitochondrial genome revealed that the majority of genes may have undergone purifying selection, exhibiting a slower rate of evolution and a relatively conserved structure. Analysis of the phylogenetic relationships among different species revealed that F. suspensa was most closely related to Olea europaea subsp. Europaea. CONCLUSION: In this study, we sequenced, assembled, and annotated a high-quality F. suspensa mitochondrial genome. The results of this study will enrich the mitochondrial genome data of Forsythia, lay a foundation for the phylogenetic development of Forsythia, and promote the evolutionary analysis of Oleaceae species.

Oxygen-limited pyrolysis and incineration impact on biochar transport.

At present, studies on biochar transport have focused on biochar obtained by oxygen-limited pyrolysis, which may differ from conventional biochar produced by incineration in nature. This work investigated the transport and retention mechanisms of three types of oxygen-limited pyrolytic biochar and three types of traditional biochar in saturated porous media. The results showed that the specific surface area of the three oxygen-limited pyrolysis biochar (180-200 m2·g-1) was higher than that of the traditional biochar (50-60 m2·g-1). Therefore, the retention capacity of pyrolytic biochar is strong and the permeability is less than 0.1. The absolute value of the zeta potential of traditional biochar is greater than 30 mV, and the electrostatic repulsion generated is stronger, with a peak penetration rate of 0.16. Moreover, the zeta potential of biochar and traditional biochar is regulated by pH value and ionic strength. In acidic conditions or solutions with high ionic strength, the zeta potentials of the six types of biochar changed to about - 15 mV, and the second minimum value was less than 0, indicating that there was a tendency for sedimentation. This study provides a new perspective for assessing the transport and environmental risks of biochar in the environment.