Zanthoxylum L. is an economic crop with a long history of cultivation and domestication and has important economic, ecological, and medicinal value. To solve the classification problems caused by the similar morphological characteristics of Zanthoxylum and establish a credible phylogenetic relationship, we sequenced and annotated six Zanthoxylum chloroplast (cp) genomes (Z. piasezkii, Z. armatum, Z. motuoense, Z. oxyphyllum, Z. multijugum, and Z. calcicola) and combined them with previously published genomes for the Zanthoxylum species. We used bioinformatics methods to analyze the genomic characteristics, contraction, and expansion of inverted repeat (IR) regions; differences in simple sequence repeats (SSRs) and long repeat sequences; species pairwise Ka/Ks ratios; divergence hotspots; and phylogenetic relationships of the 14 Zanthoxylum species. The results revealed that cp genomes of Zanthoxylum range in size from 158,071 to 158,963 bp and contain 87 protein-coding, 37 tRNA, and 8 rRNA genes. Seven mutational hotspots were identified as candidate DNA barcode sequences to distinguish Zanthoxylum species. The phylogenetic analysis strongly supported the genus Fagara as a subgenus of Zanthoxylum and proposed the possibility of a new subgenus in Zanthoxylum. The availability of these genomes will provide valuable information for identifying species, molecular breeding, and evolutionary analysis of Zanthoxylum.

Paeonia ludlowii is indigenous to Tibet and has an important ecological and economic value in China. In Tibet, P. ludlowii has been used in folk medicine with relative success. Plant microbial endophytes play an important role in plant growth, health and ecological function. The diversity of endophytic bacteria associated with P. ludlowii remains poorly understood. In this study, the structure of the endophytic bacterial communities associated with different tissues, including fruits, flowers, leaves, stems, and roots, and rhizosphere soils was analyzed with Illumina MiSeq sequencing of bacterial 16S rDNA. A total of 426,240 sequences and 4847 operational taxonomic units (OTUs) were obtained. The OTUs abundance of roots was higher than that of other tissues; however, the OTUs abundance was similar among different deep soil samples. In the plant tissues, Cyanobacteria was the most abundant bacterial phylum, followed by Proteobacteria; however, the most abundant phyla were Proteobacteria and Acidobacteria in soil samples from three different layers. In addition, the diversity and richness of the microorganisms in the soil were very similar to those in roots but higher than those in other tissues of P. ludlowii . Predictive metagenome analysis revealed that endophytic bacteria play critical functional roles in P. ludlowii . This conclusion could facilitate the study of the ecological functions of endophytic bacteria and their interactions with P. ludlowii to analyze the reasons why this important medicinal plant is becoming endangered.

No abstract

Isopentenyl diphosphate isomerase (EC 5.3.3.2, IPI) catalyzes the revisable conversion of 5-carbon isopentenyl diphosphate (IPP) and its allylic isomer dimethylallyl diphosphate (DMAPP), which are the essential precursors for isoprenoids, including anti-tumor camptothecin. Here we report cloning, characterization and functional expression of a new cDNA encoding IPI from Camptotheca acuminata. The full-length cDNA was 1143 bp long designated as CaIPI (GenBank Accession Number: DQ839416), containing an open reading frame (ORF) of 930bp which encodes a polypeptide of 309 amino acids. Bioinformatic analysis showed the cDNA sequence of CaIPI was highly homologous with other IPI gene and the deduced amino acid sequence of CaIPI was similar to known plant IPIs and contained Cys-149 and Glu-212 active sites. Phylogenic analysis indicated that all IPIs could be divided into five groups and CaIPI belonged to plant IPIs' family. The tissue expression profile analysis was carried out to investigate the transcriptional level of CaIPI in different tissues. The result showed that CaIPI expression could be detected in roots, stems and tender leaves but could not in mature leaves and fruits, and the expression levels was much higher in stems than in roots and tender leaves. Finally, CaIPI was functionally expressed in engineered Escherichia coli in which the carotenoid pathway was reconstructed. In engineered E. coli, CaIPI could facilitate the metabolic flux to the carotenoids biosynthesis and made the bacteria produce the orange beta-carotene. These confirmed that CaIPI had the typically function of IPI gene. In summary, cloning, characterization and functional expression of CaIPI will facilitate to understand the function of CaIPI at the level of molecular genetics and unveil the biosynthetic mechanism of camptothecin precursors.