Comparative analysis of the chloroplast genomes of Rosa species and RNA editing analysis.

BACKGROUND: The genus Rosa (Rosaceae) contains approximately 200 species, most of which have high ecological and economic values. Chloroplast genome sequences are important for studying species differentiation, phylogeny, and RNA editing. RESULTS: In this study, the chloroplast genomes of three Rosa species, Rosa hybrida, Rosa acicularis, and Rosa rubiginosa, were assembled and compared with other reported Rosa chloroplast genomes. To investigate the RNA editing sites in R. hybrida (commercial rose cultivar), we mapped RNA-sequencing data to the chloroplast genome and analyzed their post-transcriptional features. Rosa chloroplast genomes presented a quadripartite structure and had highly conserved gene order and gene content. We identified four mutation hotspots (ycf3-trnS, trnT-trnL, psbE-petL, and ycf1) as candidate molecular markers for differentiation in the Rosa species. Additionally, 22 chloroplast genomic fragments with a total length of 6,192 bp and > 90% sequence similarity with their counterparts were identified in the mitochondrial genome, representing 3.96% of the chloroplast genome. Phylogenetic analysis including all sections and all subgenera revealed that the earliest divergence in the chloroplast phylogeny roughly distinguished species of sections Pimpinellifoliae and Rosa and subgenera Hulthemia. Moreover, DNA- and RNA-sequencing data revealed 19 RNA editing sites, including three synonymous and 16 nonsynonymous, in the chloroplast genome of R. hybrida that were distributed among 13 genes. CONCLUSIONS: The genome structure and gene content of Rosa chloroplast genomes are similar across various species. Phylogenetic analysis based on the Rosa chloroplast genomes has high resolution. Additionally, a total of 19 RNA editing sites were validated by RNA-Seq mapping in R. hybrida. The results provide valuable information for RNA editing and evolutionary studies of Rosa and a basis for further studies on genomic breeding of Rosa species.

A combined theoretical and experimental investigation on the photocatalytic hydrogenation of CO2 on Cu/ZnO polar surface.

The photocatalytic hydrogenation of CO2 by Cu-deposited ZnO (Cu/ZnO) polar surfaces is investigated through density functional theory (DFT) calculations combined with experimental work. The DFT results demonstrate that, without Cu-loading, CO2 and H2 present weak physisorption on the clean ZnO polar surface, except that H2 undergoes strong chemisorption on the ZnO(0001̄) surface. Cu deposition on the ZnO polar surface could remarkably enhance the CO2 chemisorption ability, due to the induced charge redistribution on the interface of the Cu/ZnO polar surface systems. Additionally, a Cu-nanoisland, which was simulated using a Cu(111) slab model, exhibited strong ability to chemically adsorb H2. Thus, H2 may act as an adsorption competitor to CO2 on the Cu/ZnO(0001̄), while, in contrast, CO2 and H2 (syngas) may have more opportunity to simultaneously adsorb on Cu/ZnO(0001) to promote the CO2 hydrogenation. These facet-dependent properties lead us to assume that Cu/ZnO(0001) should be a favorable photocatalyst for CO2 hydrogenation. This assumption is further verified by our photocatalysis experiment based on a ZnO single crystal. According to the theoretical and experimental results, the optimal HCOO* reaction pathway for the photocatalytic hydrogenation of CO2 on Cu/ZnO(0001) is proposed. In this optimal HCOO* path, the hydrogenation of CO2* step and hydrogenation of HCOO* step could be promoted by the coupling of a photo-generated spillover proton and a photoelectron on the interface of Cu/ZnO(0001). This research demonstrates the feasibility of the photocatalytic reduction of CO2 on Cu/ZnO(0001), and will help to develop related high-efficiency catalysts.