ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
Anthraquinones are not only the main active constituents but also the index components for the quality control of Rhei Radix et Rhizoma. To study the anthraquinone biosynthesis, Rheum palmatum L. seedlings were subjected to a high-throughput transcriptomic sequencing analysis by Illumina HiSeqTM 2000 150PE. The Illumina sequencing generated a total of 11.04 G clean data resulting in 736 309 74 clean reads, deposited in the sequence read archive (SRA accession SRP160030). Trinity do novo assembly yielded 93 646 unigenes, with an average of 1 108 nt. Functional annotation revealed that all unigenes were successfully annotated in the NR, NT, Swiss-port, PFAM, and KOG databases. GO enrichments showed that 57 subgroups were involved in biological process, cellular component, and molecular function. KEGG analysis indicated that 1 107 unigenes were implicated in 19 standard secondary metabolic pathways. 172 unigenes were analyzed to encode 28 key enzymes during the MVA, MEP, shikimic acid, and polyketide pathways related to anthraquinone biosynthesis. 125 CYP450 and 73 UGTs unigenes were related the modification of secondary metabolites in R. palmatum L. Furthermore, seven unigenes with full length cDNAs were successfully verified by RT-PCR and sequencing analyses. Then, MISA prediction produced a number of 18 885 simple sequence repeats (SSRs). Herein, the transcriptomic gene expression profiles of R. palmatum L. and candidate genes during the anthraquinone biosynthesis pathway were obtained for the first time. The results provided basic information for subsequent gene function characterization, secondary metabolic pathway analysis, and anthraquinone biosynthesis and regulation elucidation in R. palmatum L.
ABSTRACT
The efficacy of rhIL-11 in treating thrombocytopenia and neutropenia in gamma-irradiated rhesus monkeys and the variation in curative effect due to difference of administration times were studied. Healthy rhesus monkeys were exposed to 3.0 Gy (60)Co total body irradiation (TBI) to result in pancytopenia for three weeks. Treatment with rhIL-11 (30, 60 or 120 micro g.kg(-1).day(-1)) on early days (days 0 - 13 after TBI) could significantly improve the nadir of platelet count. Although the nadir of leukocyte count was not improved, the duration below 50% of its baseline value was shortened similarly to that of platelet. During the first two weeks after TBI, erythrocyte numbers of the animals treated with these doses of rhIL-11 were lower than those of the control group at first but they became higher beginning from the third week. Four monkeys were treated with rhIL-11 at 60 micro g.kg(-1).day(-1) on days 13 - 26 after TBI. The numbers of their peripheral blood cells followed the similar decrease patterns as those of control group during the first three weeks, then they were improved rapidly. By semi-solid bone marrow cell culture it was demonstrated that rhIL-11 could stimulate bone marrow cells to form more CFU-Meg, CFU-Mix, CFU-E, BFU-E and CFU-GM in vitro. Histopathological observation revealed that bone marrow of the control group was devoid of hematopoietic cells and bleeding, being contrary to that of the group treated with rhIL-11, in which the cells proliferated actively. The results suggest that rhIL-11 can accelerate hematopoietic recovery of irradiated monkeys.