Molecular cloning and characterisation of two enzymes involved in the rosmarinic acid biosynthesis pathway of <Emphasis Type="Italic">Prunella vulgaris</Emphasis> L.

Prunella vulgaris, a widely-used medicinal perennial herb, contains various active compounds and has multifaceted medicinal activities. As the index component in P. vulgaris, rosmarinic acid (RA) is a typical phenolic acid, with significant anti-inflammatory, anti-oxidant, anti-tumour, anti-viral, and anti-microbial properties. To better understand the RA biosynthetic pathway in P. vulgaris, we isolated and cloned the cDNA sequences of putative RA synthase (PvRAS) and cytochrome P450 monooxygenase (PvCYP98A101), two important enzymes catalysing RA biosynthesis. Sequence analysis revealed that PvRAS contained an open reading frame (ORF) of 1305 bp encoding a 435-amino-acid residue belonging to the BAHD acyltransferase family, and PvCYP98A101 contained an ORF of 1530 bp encoding a 510-amino-acid residue, as a member of the CYP98A family. The deduced PvRAS and PvCYP98A101 amino acid sequences shared high similarity with other putative/known RASs and CYPs, respectively. Quantitative real-time PCR analysis showed that constitutive expression of PvRAS and PvCYP98A101 was much higher in roots than in leaves, stems, or spikes. Further analysis indicated that PvRAS was localised in the cytosol and nucleus, whilst PvCYP98A101 existed as a membrane protein in the endoplasmic reticulum. These results highlight the RA biosynthesis pathway in P. vulgaris and, provide useful information to engineer natural products.     

Characterization and Expression Analysis of a Glutathione Reductase Gene from Antarctic Moss Pohlia nutans

Glutathione reductase (GR) is a flavoprotein oxidoreductase and plays an important role in response to oxidative stresses in plants. A cDNA-encoding cytosolic GR [GenBank accession number GACA01029426, designated as Pohlia nutans glutathione reductase gene (PnGR)] was successfully cloned from Antarctic moss P. nutans. The full-length PnGR cDNA has 1,654 bp nucleotides with an open reading frame of 1,494 bp, encoding 497 amino acid residues. The deduced amino acid sequence of PnGR had 87.0 % identity with GR in Physcomitrella patens subsp. patens. The phylogenetic analysis showed that PnGR is clustered together with known cytosolic GR in other plants. In addition, the subcellular localization analysis by observing the transient expression of PnGR–green fluorescent protein fusion protein in Arabidopsis thaliana mesophyll protoplasts also revealed PnGR targeting to cytosol in plant cells. The expression patterns of PnGR under different abiotic stresses were determined by real-time PCR. Compared to the normal condition, the maximal mRNA accumulation of PnGR increased 3.82-fold at 4 °C, 2.92-fold at 10 °C, 4.14-fold with 200 mM NaCl, and 3.17-fold with drought stress, respectively. Together, our results suggested that the inducible PnGR might play an important role in Antarctic moss P. nutans acclimatizing to polar environment.     

Molecular cloning and sequence analysis of methionine adenosyltransferase from the economic seaweed Undaria pinnatifida

The methionine adenosyltransferase gene (MAT) had been isolated from an economic seaweed Undaria pinnatifida by PCR using degenerate primers. The cDNA was 1,491 bp in length with an open reading frame of 1,194 nucleotides, encoding a deduced protein of 397 amino acids. The protein had a predicted molecular weight of 43.2 kDa, and the isoelectric point was 5.244. The sequence contains a 92 bp 5′-untranslated region (UTR) and a 205 bp 3′-UTR. The methionine adenosyltransferase (MAT) sequence of U. pinnatifida (UpMAT) shared 68–92 % identities with the previous published MAT sequences of other species. Phylogenetic analysis indicated that the phylogenetic relationship of UpMAT with some other seaweeds was closer than with those of higher plants. Under different stress conditions, the relative mRNA expression levels of the MAT of U. pinnatifida (UpMAT) were measured by real-time quantitative PCR, and the results demonstrated that the UpMAT might help to protect the alga against various abiotic stresses.     

Cloning and expression of <Emphasis Type="Italic">Perilla frutescens FAD2</Emphasis> gene and polymorphism analysis among cultivars

?12 fatty acid desaturase (FAD2) is a key enzyme for linoleic acid and linolenic acid biosynthesis. Perilla frutescens is a special oil plant species with highest linolenic acid content. In this study, based on RACE, two alleles for one FAD2 gene were isolated from P. frutescens cultivar C2: the 3956 bp PfFAD2a and the 3959 bp PfFAD2b, both with a full-length cDNA of 1526 bp, and both encoding a 382aa basic protein. The alleles have identities of over 98%, and their encoded proteins differ only by substitution of a strongly similar residue. Saccharomyces cerevisiae heterologous expression suggested that PfFAD2a/b both encode a bio-functional FAD2 enzyme. Phylogenetic analyses indicated that PfFAD2 shows the highest homologies to FAD2 genes from dicots such as Boraginaceae and Burseraceae. PfFAD2a/b expressions are mainly restricted to developing seeds. PfFAD2a/b expression in the seedling leaf is upregulated by cold (4 °C) and repressed by heat (42 °C). Each of the eight cultivars contains two alleles for one PfFAD2 and 40 SNP sites are found. One allelic gene in cultivars C1 and P1 is pseudogene because of premature stop codon mutation in 5′ coding region. All other normal PfFAD2 genes/allelic genes encode identical or very similar proteins. PfFAD2a/b expression level in developing seeds also varies among the eight cultivars. This study provides systemic molecular and functional features of PfFAD2 and enables its application in the study of plant fatty acids traits.     

Isolation and Characterization of the PKAr Gene From a Plant Pathogen,Curvularia lunata

By using EST database from a full-length cDNA library of Curvularia lunata, we have isolated a 2.9 kb cDNA, termed PKAr. An ORF of 1,383 bp encoding a polypeptide of 460 amino acids with molecular weight 50.1 kDa, (GeneBank Acc. No. KF675744) was cloned. The deduced amino acid sequence of the PKAr shows 90 and 88 % identity with cAMP-dependent protein kinase A regulatory subunit from Alternaria alternate and Pyrenophora tritici-repentis Pt-1C-BFP, respectively. Database analysis revealed that the deduced amino acid sequence of PKAr shares considerable similarity with that of PKA regulatory subunits in other organisms, particularly in the conserved regions. No introns were identified within the 1,383 bp of ORF compared with PKAr genomic DNA sequence. Southern blot indicated that PKAr existed as a single copy per genome. The mRNA expression level of PKAr in different development stages were demonstrated using real-time quantitative PCR. The results showed that the level of PKAr expression was highest in vegetative growth mycelium, which indicated it might play an important role in the vegetative growth of C. lunata. These results provided a fundamental supporting research on the function of PKAr in plant pathogen, C. lunata.     

Effect of strigolactones and auxins on growth and metabolite content of Sutherlandia frutescens (L.) R. Br. microplants in vitro

The influence of strigolactones as hormones in plants is not fully characterised even though they are known to affect plant architecture, both above ground and in the roots. Using an in vitro system, the effects of the synthetic auxins 1-naphthalene acetic acid and indole-3-butyric acid (NAA and IBA) and synthetic strigolactones (GR24 and Nijmegen-1) were tested on microplant development of Sutherlandia frutescens, a leguminous medicinal plant native to South Africa. Considerable phytochemical variation in wild populations has led to the proposal of using micropropagation for this species. This will assist with domestication and provide plants with a more predictable chemistry for the phytopharmaceuticals industry. Nodal explants with an axillary bud were grown on Murashige and Skoog (Plant Physiol 15:473–497, 1962) medium [0.8 % (m/v) agar (pH 5.8), 3 % (m/v) sucrose and 0.1 g/L myo-inositol] supplemented with NAA, IBA, GR24 and Nijmegen-1, either singly or in combination. The amino acid profile and secondary metabolite pool was monitored using LC–MS-profiling. Treatment with NAA promoted mass shoot production, whilst a combination of NAA and Nijmegen-1 also positively influenced the accumulation of amino acids, flavonoids (sutherlandins) and terpenoids (sutherlandiosides) that S. frutescens produces. Since these compounds represent the presumed active compounds in this species and the biomarkers used in quality control assessment of S. frutescens tissues harvested for the pharmaceutical industry, this treatment holds promise for the commercial production of Sutherlandia extracts and herbal medications.     

Molecular cloning and characterization of SoNCED, a novel gene encoding 9-cis-epoxycarotenoid dioxygenase from sugarcane (Saccharum officinarum L.)

Abscisic acid (ABA) plays important roles in adaptive responses to various environmental stresses. The rate-limiting step in ABA biosynthesis is the oxidative cleavage of cis-epoxycarotenoids, which is catalyzed by 9-cis-epoxycarotenoid dioxygenase (NCED). In this experiment, a full-length cDNA encoding NCED gene was cloned by RT-PCR and RACE from sugarcane (Saccharum officinarum L.). The full-length of SoNCED is 2,521 bp with 1,827 bp open reading frame, encoding a peptide of 608 amino acids. The calculated molecular weight of protein was 65.9 kDa with isoelectric point of 6.04. Conserved domains prediction indicated a chloroplast-targeting peptide located at N-terminus of SoNCED. Phylogenetic tree, constructed by Neighbor-Joining method indicated that SoNCED shared high identity with the NCEDs reported from other plant species. Sequence alignment revealed that the basic secondary structure including α-helices, β-strands, β-propeller and His residues coordinating catalytic sites of SoNCED were highly conserved as in the NCEDs from other plants. Tissue specific expression analysis using quantitative real-time PCR showed a significant increase in SoNCED mRNA level and its correlation with O₂ ^– production rate and ABA accumulation in leaves and roots of sugarcane variety GT21 when exposed to water stress. Further, the stimulation of SoNCED mRNA level, O₂ ^– production rate and ABA content after exogenous application of ABA (100 μMol l^?1) proved its involvement in pathways providing tolerance to drought stress.     

Molecular cloning, characterization and expression of PmRsr1, a Ras-related gene from yeast form of Penicillium marneffei

GTP-binding proteins such as Ras act as molecular switches in a large number of signal pathways. In this report, we isolated and characterized a novel Ras small monomeric GTPase Rsr1 gene, designated PmRsr1, from yeast-form Penicillium marneffei. The full-length PmRsr1 cDNA sequence is 1,866 bp in size, and contains an open reading frame of 642 bp encoding 213 amino acids. The predicted molecular mass of PmRsr1 is 24.41 kDa with an estimated theoretical isoelectric point of 9.21. The deduced amino acid sequence of PmRsr1 shows 87% identity with that of Aspergillus fumigatus and A. clavatus. Eight exons and seven introns are identified within the 2,102 bp PmRsr1 genomic DNA sequence of P. marneffei. The open reading frame was subcloned into the pcDNA6-myc-His B expression vector, and the recombinant plasmid was transfected into Vero cell line. The expressed fusion protein was analyzed by SDS-PAGE and western blotting. Differential expression of the PmRsr1 was demonstrated by real-time RT-PCR. The expression of PmRsr1 was the highest in the yeast phase comparing with that in the mycelia and conidia phases.     

OsDOG, a gibberellin-induced A20/AN1 zinc-finger protein, negatively regulates gibberellin-mediated cell elongation in rice

The A20/AN1 zinc-finger proteins (ZFPs) play pivotal roles in animal immune responses and plant stress responses. From previous gibberellin (GA) microarray data and A20/AN1 ZFP family member association, we chose Oryza sativa dwarf rice with overexpression of gibberellin-induced gene (OsDOG) to examine its function in the GA pathway. OsDOG was induced by gibberellic acid (GA₃) and repressed by the GA-synthesis inhibitor paclobutrazol. Different transgenic lines with constitutive expression of OsDOG showed dwarf phenotypes due to deficiency of cell elongation. Additional GA₁ and real-time PCR quantitative assay analyses confirmed that the decrease of GA₁ in the overexpression lines resulted from reduced expression of GA3ox2 and enhanced expression of GA2ox1 and GA2ox3. Adding exogenous GA rescued the constitutive expression phenotypes of the transgenic lines. OsDOG has a novel function in regulating GA homeostasis and in negative maintenance of plant cell elongation in rice.     

Molecular characterization of a short peptidoglycan recognition protein (PGRP-S) from Asian corn borer (Ostrinia furnacalis) and its role in triggering proPO activity

Peptidoglycan recognition proteins (PGRPs) are non-specific immune molecules of insects, and vertebrates etc., but are not present in plants and nematodes. In the current experiment, a PGRP DNA sequence (2,910 bp containing four exons) was identified from genomic DNA library of Asian corn borer, Ostrinia furnacalis, and a full-length cDNA programming PGRP was cloned (designed as OfPGRP-S) with an open reading frame of 579 bp, having 192 amino acid. This inferred amino acid sequence showed maximum similarity to known lepidopteran PGRPs. Quantitative real-time PCR investigation disclosed the level of mRNA of OfPGRP-S to be constitutively expressed in the whole developmental stages and with higher expression in the mature larvae. Even more the OfPGRP-S was mainly expressed in immune capable organs i.e., fat body and midgut, and was strongly induced by injecting gram-positive bacteria i.e., Staphylococus aureus. Recombinant protein OfPGRP-S could bind to S. aureus and Bacillus thuringiensis which enhance proPO activation in the presence of these microbes. The results indicated that OfPGRP-S is an inducible protein acting as a receptor-type PGRP for enhancing the proPO activation on exposure to bacteria.     

Isolation and characterization of a C-repeat binding factor (CBF)-like gene in cassava (Manihot esculenta Crantz)

Cassava (Manihot esculenta Crantz) is a tropical and subtropical plant and susceptible to chilling injury. In this research, a C-repeat binding factor (CBF)-like gene (GenBank accession number JQ339740) has been isolated from cassava, and named as MeCBF1. The full-length DNA of MeCBF1 is 1,037 base pair (bp), without intron. The 5′ untranslated region is 102 bp, the 3′ untranslated region is 239 bp, and the open reading frame is 696 bp encoding 231 amino acids. The deduced amino acid sequence of MeCBF1 contains two CBF conserved motifs of PKK(P/R)AGRxKFxETRHP and DSxWR. The MeCBF1 shows 83 % homology to the CRT/DRE binding factor 1 from Hevea brasiliensis (Accession no. AAY43213.1). However, in cassava, the MeCBF1 target genes showed low similarity to the CBF/DREB regulated genes in Arabidopsis thaliana. Quantitative real-time PCR showed that the MeCBF1 was highly expressed in stems and leaves, and lowly expressed in roots. In addition, the expression of the MeCBF1 quickly responded to low temperature stress (4 °C). These results suggest that, the MeCBF1 is functional in cassava. Further studies on the MeCBF1 might be helpful to reveal molecular mechanism of cassava’s high sensitivity to low temperature.     

Cloning and characterisation of rosmarinic acid synthase from Melissa officinalis L

Lemon balm (Melissa officinalis L.; Lamiaceae) is a well-known medicinal plant mainly due to two groups of compounds, the essential oil and the phenylpropanoid derivatives. The prominent phenolic compound is rosmarinic acid (RA), an ester of caffeic acid and 3,4-dihydroxyphenyllactic acid. RA shows a number of interesting biological activities. Rosmarinic acid synthase (RAS; 4-coumaroyl-CoA:hydroxyphenyllactic acid hydroxycinnamoyltransferase) catalyses the ester formation. Cell cultures of M. officinalis have been established in order to characterise the formation of RA in an important diploid medicinal plant. RAS activity as well as the expression of the RAS gene are closely correlated with the accumulation of RA in suspension cultures of M. officinalis. The RAS cDNA and gene (MoRAS) were isolated. The RAS gene was shown to be intron-free. MoRAS belongs to the BAHD superfamily of acyltransferases. Southern-blot analysis suggests the presence of only one RAS gene copy in the M. officinalis genome. The enzyme was characterised with respect to enzyme properties, substrate preferences and kinetic data in crude plant extracts and as heterologously synthesised protein from Escherichia coli.     

Molecular characterization and differential expression studies of an oxidosqualene cyclase (OSC) gene of Brahmi (Bacopa monniera)

Triterpenoid saponins are the class of secondary metabolites, synthesized via isoprenoid pathway. Oxidosqualene cyclases (OSCs) catalyzes the cyclization of 2, 3-oxidosqualene to various triterpene skeletons, the first committed step in triterpenoid biosynthesis. A full-length oxidosqualene cyclase cDNA from Bacopa monniera (BmOSC) was isolated and characterized. The open reading frame (ORF) of BmOSC consists of 2,292 bp, encoding 764 amino acid residues with an apparent molecular mass of 87.62 kDa and theoretical pI 6.21. It contained four QxxxxxW motifs, one Asp-Cys-Thr-Ala-Glu (DCTAE) motif which is highly conserved among the triterpene synthases and another MWCYCR motif involved in the formation of triterpenoid skeletons. The deduced amino acid sequence of BmOSC shares 80.5 % & 71.8 % identity and 89.7 % & 83.5 % similarity with Olea europaea mixed amyrin synthase and Panax notoginseng dammarenediol synthase respectively. Phylogenetic analysis revealed that BmOSC is closely related with other plant OSCs. Quantitative real-time PCR (qRT-PCR) data showed that BmOSC is expressed in all tissues examined with higher expression in stem and leaves as compared to roots and floral parts.     

斑茅δ-OAT基因克隆及其序列分析

利用RT-PCR和RACE技术从斑茅（Erianthus arundinaceus）中分离出编码鸟氨酸-δ-氨基转氨酶基因的全长cDNA序列,序列全长1 680 bp,编码454个氨基酸。通过对哺乳动物、高等植物、微生物的δ-OAT基因编码的氨基酸序列进行同源比对,发现斑茅δ-OAT基因同其近缘属植物甘蔗的同源性最高（87%）,同其他高等植物的同源性次之（约为70%）,而同动物的同源性最低（约为60%）。在斑茅δ-OAT基因编码的氨基酸序列的5′端未发现线粒体定位序列,同甘蔗δ-OAT基因一样。斑茅δ-OAT基因具有完整的鸟氨酸转氨酶功能区rocD。利用定量RCR（real-time PCR）对30%PEG胁迫下的斑茅δ-OAT基因表达量进行研究,结果表明δ-OAT基因在胁迫12 h表达量达到最高,约为对照的4.1倍;胁迫2 h δ-OAT基因表达量反而有所降低。