Cloning, expression analysis and enzyme activity verification of dihydroflavonol 4-reductase from Cistanche tubulosa (Schenk) Wight flower / 药学学报

Dihydroflavonol 4-reductase (DFR) plays an essential role in the biosynthesis of anthocyanin and regulation of plant flower color. Based on the transcriptome data of Cistanche tubulosa (Schenk) Wight, a full-length cDNA sequence of CtDFR gene was cloned by reverse transcription-polymerase chain reaction (RT-PCR). CtDFR contains an open reading frame (ORF) of 1 263 bp which encodes 420 amino acids with a predicted molecular weight of 47.5 kDa. The sequence analysis showed that CtDFR contains a nicotinamide adenine dinucleotide phosphate (NADPH) binding domain and a specific substrate binding domain. The expression analysis indicated that CtDFR was highly expressed in red and purple flowers, and the relative expression levels were 4.04 and 19.37 times higher than those of white flowers, respectively. The recombinant CtDFR protein was expressed in E.coli BL21 (DE3) using vector pET-28a-CtDFR and was purified. In vitro enzyme activity analysis, CtDFR could reduce three types of dihydroflavonols including dihydrokaempferol, dihydroquercetin, and dihydromyricetin to leucopelargonidin, leucocyanidin and leucodelphinidin. Subcellular localization analysis showed that CtDFR was mainly localized in the cytoplasm. These results demonstrate that CtDFR plays an important role in regulation of flower color in C. tubulosa and make a valuable contribution for the further investigation on the regulation mechanism of C. tubulosa (Schenk) Wight flower color.

Cloning, expression and functional identification of cytochrome P450 reductase gene in Aquilaria sinensis / 药学学报

Cytochrome P450 reductase (CPR) is essential for the electron transport chain of cytochrome P450s, playing an indispensable role in electron transfer in vivo. In this study, one cDNA encoding cytochrome P450 reductase (Ascpr1) was identified from the callus of Aquilaria sinensis. Ascpr1 contains an open reading frame of 2 124 bp. The deduced protein is composed of 707 amino acids, with a predicted molecular weight of 78.82 kD. Phylogenetic analysis revealed that AsCPR1 is a type Ⅱ CPR protein closely related to the CPR from Theobroma cacao. Transmembrane prediction using TMHMM 2.0 indicated that the amino acids 52-71 of AsCPR1 comprise a transmembrane region. After truncating of 67 amino acid residues from N-terminal, the truncated AsCPR1 was successfully expressed in E. coli Transetta (DE3). Further purification of the recombinant AsCPR1 by affinity chromatography and determination of the enzymatic activity allowed the reducing ability of AsCPR1 to cytochrome C in vitro. The results pave the way for further study on the synthesis of defensive chemicals involved in P450s and the functions of CPR in self-defense of A. sinensis.

Cloning and expression analysis of chalcone isomerase from Aquilaria sinensis / 药学学报

Chalcone isomerases (CHIs) play an essential role in the biosynthesis of flavonoids important in plant self-defense. Based on the transcriptome data of Aquilaria sinensis Calli, a full-length cDNA sequence of CHI1 (termed as AsCHI1) was cloned by reverse transcription PCR. AsCHI1 contains a complete open frame (ORF) of 654 bp. The deduced protein is composed of 217 amino acids, with a predicted molecular weight of 23.11 kDa. The sequence alignment and phylogenetic analysis revealed that AsCHI1 has conserved most of the active site residues in type I CHIs, indicating a close relationship with the CHI from Gossypium hirsutum. The recombinant AsCHI1 protein was obtained by heterologous expression of AsCHI1 in E. coli BL21(DE3). The purified AsCHI1 protein exhibited CHI activity by catalyzing the production of naringenin from naringenin chalcone. Remarkably, AsCHI1 expression in A. sinensis Calli treated with various abiotic stresses including salt, mannitol, cold, and heavy metals could be markedly increased, and plant hormones such as abscisic acid (ABA), gibberellin (GA3), and salicylic acid (SA) could also increase the expression of AsCHI1, suggesting that AsCHI1 might play an important role in plant self-defense. The results expand our understanding of the biosynthesis of flavonoids in A. sinensis and give further insight into the defensive responses of A. sinensis to abiotic and biotic stresses.

Cloning and expression analysis of S-adenosylmethionine synthetase gene from Aquilaria sinensis / 药学学报

S-adenosylmethionine synthetase, a key enzyme in plant metabolism, plays an essential role in the plant defence system. In present study, a full length cDNA sequence of AsSAMS1 gene was cloned by RACE and reverse transcription PCR from Aquilaria sinensis calli. Meanwhile, the bioinformatics, prokaryotic expression, tissue-specific expression analysis, and expression analysis under different abiotic stresses and hormone treatments were performed. The open reading frame (ORF) of AsSAMS1 gene was 1 183 bp, encoding a protein of 393 amino acids with a calculated molecular mass (MW) of 43.13 kDa. Bioinformatic analysis indicated that AsSAMS1 contained 3 SAMS characteristic sequences. The phylogenetic analysis indicated that AsSAMS1 protein had the highest level of homology with SAMS protein from Glycine soja. The recombinant AsSAMS1 protein was successfully expressed in Escherichia coli BL21 (DE3) cells using the prokaryotic expression vector pET28a-AsSAMS1 and the recombinant AsSAMS1 was purified by Ni2+ affinity chromatography. Expression analysis results in different tissues indicated that AsSAMS1 was primarily observed in stems, and then stem tips and leaves, following by roots. The transcript level of AsSAMS1 and the content of S-adenosylmethionine (SAM) were induced by various abiotic stresses including salt, drought, cold, and heavy metal stress. Furthermore, AsSAMS1 expression level was enhanced upon methyl jasmonate (MeJA), salicylic acid (SA), gibberellin (GA3), and abscisic acid (ABA) treatment. These results provided valuable insights for further study on the role of SAMS in the mechanism of agarwood formation and plant resistance.

Cloning and expression analysis of allene oxide cyclase gene from Aquilaria sinensis / 药学学报

Allene oxide cyclase (AOC), a key enzyme in biosynthesis of jasmonic acid, plays an essential role in the plant defense system. In present study, a full length cDNA of AsAOC gene was cloned by the reverse transcription PCR from Aquilaria sinensis calli. Meanwhile, the bioinformatics, prokaryotic expression, purification, tissue-specific expression analysis, and expression analysis under different abiotic stresses and hormone treatments were performed. The open reading frame (ORF) of AsAOC1 gene was 753 bp, encoding a protein of 251 amino acids with a calculated molecular mass (MW) of 27.46 kD. Bioinformatic analysis showed that AsAOC1 protein contains a conserved allene_ox_cyc domain in C-terminus. The phylogenetic analysis indicated that AsAOC1 protein had the highest level of homology with the AOC protein from Morus notabilis. The recombinant AsAOC1 protein was successfully expressed in Escherichia coli BL21(DE3) cells using the prokaryotic expression vector pET28a-AsAOC1 and was purified by Ni2+ affinity chromatography. Expression analysis in different tissues indicated that AsAOC1 was primarily observed in stems, and then stem tips and roots, following by leaves. The transcript level of AsAOC1 was induced by various abiotic stresses including salt, drought, cold, and heavy metal stress. Furthermore, AsAOC1 expression level was enhanced upon methyl jasmonate (MeJA), salicylic acid (SA), gibberellin (GA3), and abscisic acid (ABA) treatments. These results provide valuable insights into the role of JA in the mechanism of agarwood formation and plant defense system.

Cloning and expression analysis of glucose-6-phosphate dehydrogenase 1 (G6PDH1) gene from Chimonanthus praecox / 中国中药杂志

Glucose-6-phosphate dehydrogenase is main regulatory enzyme for pentose phosphate pathway. To amplify the core sequence of G6PDH gene from Chimonanthus praecox, the primers were synthesized, based on the conserved nucleotide sequence of other reported plant G6PDH genes. The specific primers were designed according to the major fragment. The full length cDNA of the G6PDH1 gene was isolated by the 3' and 5' rapid amplification of cDNA ends approach. Transcript levels of G6PDH1 isoform was measured by real-time quantitative RT-PCR in different tissues and in responds to cold treatment. The G6PDH1 subcellular localization, transmembrane domain, three-dimensional structure, and phylogenetic analysis were predicted by different software to analysis the bioinformatics of G6PDH1 protein. The G6PDH1 cDNA sequence was 2 011 bp in length and consisted of 1 551 bp Open Reading Frame (ORF) , encoding a protein of 516 amino acids. Expression analysis results in different tissues showed that G6PDH1 was primarily observed in flowers and roots, as opposed to the leaves and stems. Cold treatment experiments indicated that cold treatment caused a rapid increase in G6PDH1 expression in flowers within 12 h. The full-length cDNA of G6PDH1 and its expression analysis will play an important role for further study on cold stress responses in Ch. praecox.