Characterization of the complete chloroplast genome of Polygonatum franchetii Hua, a Chinese endemic medicinal species, and phylogenetic relationships of Polygonatum / 药学学报

italic>Polygonatum franchetii Hua is a medicinal plant endemic to China from Polygonatum Mill. The chloroplast genomes of two P. franchetii individuals sampled from two different habitats were sequenced by using the DNBSEQ-T7 high-throughput sequencing platform. After assembly and annotation, the two complete chloroplast genomes were characterized, and then comparative and phylogenetic analyses were performed with other published chloroplast genome sequences from Polygonatum. The whole chloroplast genomes of the two P. franchetii individuals were 155 942 and 155 962 bp in length, with a large single copy region (LSC, 84 670 and 84 722 bp), a small single copy region (SSC, 18 564 and 18 566 bp) and a pair of reverse repeats (IRa/IRb, 26 354 and 26 337 bp), respectively. Both of them contained 113 genes, including 79 protein-coding genes (PCGs), 30 transfer RNA (tRNA) genes, and 4 ribosomal RNA (rRNA) genes. Comparative analyses showed that the genome length, the guanine and cytosine (GC) content, genes content and order were highly conserved between the two P. franchetii individuals and among different Polygonatum species. The detected repeat sequences, including dispersed repeats, tandem repeats and simple sequence repeats (SSRs), were also relatively similar in types and positions, though showing a slightly difference in number. No significant expansion or contraction of the inverted repeat regions was found. Sequences variation between the two P. franchetii individuals was lower than that among different Polygonatum species. Besides, coding sequences (CDS) showed less divergence than noncoding sequences, and sequence divergence of IRs regions was lower than that of the LSC and SSC regions, both intraspecifically and interspecifically. Eight sequences with high nucleotide diversity among different species were screened, all of which were found located in the LSC and SSC regions. Phylogenetic inference showed that all Polygonatum species clustered into a monophyletic clade with a 100% bootstrap value, within which, species in section Verticillata formed a distinct group, section Sibirica and section Polygonatum were sister groups. The two P. franchetii individuals grouped together and showed the closest phylogenetic affinity to P. stenophyllum Maxim., belonging to the section Verticillata. The chloroplast genome of P. franchetii and its phylogenetic position in Polygonatum were comprehensively investigated and clearly elucidated in this study, the results may lay a foundation for the resource development and utilization of P. franchetii, as well as further molecular identification and phylogenetic studies of medicinal Polygonatum species.

Identification and analysis of R1-MYB gene family in Rheum palmatum L. based on full-length transcriptome sequencing / 药学学报

As one kind of v-myb avian myeloblastosis viral oncogene homolog (MYB) transcription factors, R1-MYB (MYB-related) family plays an important role in plant growth and development, as well as environmental stress and hormone signal transduction. In this study, R1-MYB family genes in Rheum palmatum L. were systematically screened based on full-length transcriptome sequencing analysis. Firstly, the physicochemical, protein domain and molecular evolution characteristics of the coding proteins were analyzed. Furthermore, the tissue expression levels of R1-MYB genes were analyzed by RNA-seq. We also investigated the expression pattern of RpMYB24 in response to various hormones and abiotic stresses. The results showed that a total of 49 R1-MYB genes were identified, which mainly encoded thermally stable hydrophilic proteins. Most of the deduced proteins were predicted to locate in nucleus. Each protein had a large proportion of random curl and α helix, and also had the W-type conserved amino acids which were the signature of MYB. R1-MYB family members were distributed in five subgroups, including circadian clock associated 1 (CCA1)-like, I-box (GATAAG)-like, CAPRICE (CPC)-like, telomere repeat binding factor (TRF)-like and TATA binding protein (TBP)-like, and the number of CCA1-like was the majority. RNA-seq revealed that 49 R1-MYB genes were differentially expressed in roots, rhizomes and leaves of R. palmatum, and the expression levels of 15 and 23 genes in roots and rhizomes were higher than those in leaves, respectively. RpMYB24 transcript was induced by abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA) treatment, and could also significantly respond to injury, low temperature and high temperature stresses except drought stress. This study systematically identified the R1-MYB family genes and their molecular characteristics, better for further gene functional validation, and then provide a scientific basis for the transcriptional regulation mechanism research into rhubarb quality formation.

Cloning and expression characteristics of a transcription factor gene RpMYB4 in Rheum palmatum L / 药学学报

MYB transcription factors play many important regulatory roles in plant growth and development, secondary metabolism, and stress adaptation processes. In this work, an MYB gene containing a complete open reading frame (ORF) was selected from the transcriptome database of R. palmatum L. RpMYB4 ORF and cloned, encoding a polypeptide of 245 amino acids with a molecular weight of 26.99 kDa. RpMYB4 lacks a signal peptide or transmembrane domain but contains two conserved DNA binding domains (HTH-MYB) of the R2R3-MYB subfamily at the N-terminus. Multiple-sequence alignment demonstrated that RpMYB4 shared as high as 61% identity with many MYB proteins from other species. Phylogenetic analysis showed that RpMYB4 had the closest relationship with FtMYB8 and was clustered in the S4 subfamily. Subcellular localization by confocal microscopy showed that an RpMYB4-GFP-fusion protein localized to the nucleus in tobacco. Real-time fluorescence quantitative PCR analyses revealed that RpMYB4 was differentially expressed in various tissues, with the highest expression in leaves, followed by petioles, rhizome, and roots, and with the lowest level in mature seeds. After treatment of R. palmatum L. seedlings with 200 μmol·L-1 MeJA, the expression of RpMYB4 in leaves was down-regulated within 24 h, and significantly up-regulated after 200 μmol·L-1 SA treatment at 12 h and 24 h. However, gene expression did not change with 200 μmol·L-1 ABA treatment. The transcripts of RpMYB4 under drought, high temperature, and mechanical injury stresses reached a peak at 24 h, 24 h, and at 3 h, respectively, while RpMYB4 expression was inhibited by low temperature stress, reaching its lowest value at 6 h. The gene showed no significant response to salt stress. Overall, RpMYB4 was cloned from R. palmatum L. for the first time, showed high expression in leaves, and was responsive to SA and various abiotic stress treatments including drought, high temperature, and mechanical injury. The results will be useful for further analysis of secondary metabolism and stress adaptations in R. palmatum L.

Complete plastid genomes of Bupleurum chinense DC. and B. boissieuanum H. Wolff, with comparative and phylogenetic analyses of medicinal Bupleurum species / 药学学报

italic>Bupleurum L. (Apiaceae) is an economically important genus, in which many species are of medicinal value. In this study, the complete plastid genomes (plastomes) of B. chinense DC. and B. boissieuanum H. Wolff were sequenced and their characteristics were investigated. Comparative and phylogenetic analyses were conducted with other published Bupleurum plastomes. The complete plastomes of B. chinense and B. boissieuanum were 155 458 and 155 800 bp in length, and both exhibited the typical quadripartite circular structure consisting of a large single copy region (LSC, 85 343 and 85 804 bp), a small single copy region (SSC, 17 495 and 17 410 bp), and a pair of inverted repeat regions (IRa/b, 26 310 and 26 293 bp), respectively. A total of 129 genes, including 84 protein-coding genes, 37 transfer RNA (tRNA) genes, and eight ribosomal RNA (rRNA) genes were identified from each of the two plastomes. Repeat sequences detected were similar in types and distribution patterns, but the numbers were slightly different. Comparative analyses revealed that the Bupleurum plastomes were highly conserved in length, structure, the guanine and cytosine (GC) content, and gene content and order, both intraspecifically and interspecifically, and no obvious expansion or contraction of the inverted repeat regions occurred. Sequence variation was lower within the same species than among different species, noncoding sequences (including intergenic regions and introns) showed a higher divergence than the protein-coding sequences, and sequences in the LSC and SSC regions were more divergent than those in the IR regions. In addition, 11 sequences with higher nucleotide diversity among species were detected in the LSC and SSC regions. All studied Bupleurum species were inferred forming a monophyletic group with a 100% bootstrap value. Bupleurum chinense and B. boissieuanum were phylogenetically closest to B. commelynoideum and B. falcatum, separately, with all three B. chinense accessions clustered into a distinct clade. These results provide genetic information for further species identification, phylogenetic resolution, and will assist in exploration and utilization of medicinal Bupleurum species.

Use of ITS2 and psbA-trnH DNA barcode sequences of wild Phytolacca resources in Guanzhong area of Shaanxi Province / 药学学报

In order to explore the use of DNA barcode in the identification of wild Phytolacca resources in the Shaanxi Guanzhong area, 29 DNA samples were amplified and sequenced by using the universal primers ITS2 and psbA-trnH. The sequences were spliced and proof-read by Codon CodeA aligner V3.0, followed by blast comparison and identification analysis; mega 6.0 was used to analyze sequence characteristics, Kimura 2-Parameter (K2P) was used to analyze distance and intraspecific or interspecific variation, and Neighbor-Joining trees were established to evaluate the ability of two pairs of candidate sequences to distinguish Phytolaccae Radix from its adulterants. The results showed that the success rate of PCR amplification and sequencing of ITS2 and psbA-trnH was 100%; the NJ tree showed that both ITS2 and psbA-trnH sequences could separate P. acinosa, P. americana, other species of the same genus like P. japonica, P. exiensis and two adulterant species into a single clade; primer ITS2 had an advantage over psbA-trnH in determining interspecific genetic distances. Therefore, both ITS2 and psbA-trnH sequences can be used for identification of Phytolacca and their adulterants, which provides a theoretical basis for the distribution of wild Phytolacca resources and their rational development and utilization.

Complete chloroplast genome of Paeonia mairei H. Lév.: characterization and phylogeny / 药学学报

The whole chloroplast genome ofthe medicinal plant Paeonia mairei H. Lév. was sequenced using the Illumina HiSeq X Ten platform and then assembled, annotated, and characterized by bioinformatic methods in this study. The complete chloroplast genome of P. mairei is 152 731 bp in length with the typical quadripartite structure, which consists of a large single copy-region (LSC, 84 402 bp), a small single copy-region (SSC, 16 969 bp), and a pair of inverted repeat regions (IRa and IRb, 25 680 bp), with an overall GC content of 38.4%. A total of 136 predicted genes, including 90 protein-coding genes, 38 tRNA genes and eight rRNA genes were identified. Among these, seven protein-coding genes, seven tRNA genes and four rRNA genes were found duplicated in the IR regions. In addition, 28 dispersed repeats, 10 tandem repeats, and 64 simple sequence repeats were detected within the whole chloroplast genome of P. mairei. Comparative analyses between 12 Peaonia species showed that the chloroplast genomes are highly conserved in length, gene content, gene order, and GC content. Meanwhile, the noncoding sequences (intergenic regions and introns) show a higher variation than the protein coding sequences, and sequences from the LSC region and SSC region are more variable than those from the IR regions. P. mairei was inferred forming in a distinct clade with P. lactiflora, P. obovate, and P. anomala subsp. veitchii with a 100% bootstrap value and is phylogenetically closest to P. lactiflora. These results may provide a basis for further genetic studies and the development and utilization of medicinal P. mairei.

Cloning and expression analysis of gene DoSRK2E in Dendrobium officinale / 中草药

Objective To clone the SnRK2 gene in Dendrobium officinale and investigate its characteristics and expression pattern. Methods RT-PCR and RACE techniques were used to clone the full-length cDNA of DoSRK2E, with the aids of a series of online bioinformatic software, characteristics including molecular mass, isoelectric point, conserved domain, transmembrane structure, signal peptide, and subcellular localization of the deduced protein were analyzed. Besides, the sequence of the deduced protein was aligned with those of other plant SnRK2 by DNASTAR, and phylogenetic relationships were reconstructed utilizing MEGA. Finally, tissue specific expression pattern of DoSRK2E was tested by quantitative real-time PCR (qRT-PCR). Results The full-length cDNA of DoSRK2E (GenBank accession API65110) is 1 795 bp with a 1 086 bp complete open reading frame (ORF). The predicted molecular mass and isoelectric point of the deduced protein DoSRK2E were 40 850 and 4.80, respectively. No signal peptide nor transmembrane region were detected, this protein contains one protein kinase domain, one ATP binding site, and one Ser/Thr active site, which was predicted most likely to be located in the endoplasmic reticulum membrane. DoSRK2E protein showed high similarity with those from other plant SnRK2, and its phylogenetic location was in Group III of SnRK2 subfamily, and phylogenetically closest to AtSnRK2.6 from Arabidopsis. In addition, qPCR analysis revealed that DoSRK2E showed the highest expression level in root, followed by stem and leaf. Conclusion A SnRK2 family gene DoSRK2E was cloned from the rare and endangered medicinal plant D. officinale for the first time. The Characteristics and expression pattern of this gene were analyzed. This study will provide a basis for further exploration of the regulation mechanisms of DoSRK2E in D. officinale under stress conditions.