Search

Astaxanthin possesses various biological properties and is used in the animal and fish feed, food, and beverage industries. In this study, we derived zeaxanthin biosynthesis genes (crtE, crtB, crtI, crtY, and crtZ) from Erwinia uredovora and crtW from Agrobacterium aurantiacum. We fused inducible and constitutive promoters to astaxanthin biosynthesis genes to construct a novel plasmid (dubbed PTP3-6) that can effectively enhance free-form astaxanthin (FFAX) production. The PTP3-6 plasmid contains one T7 promoter, driving IPTG inducible crtW expression, and three constitutive promoters (isolated from E. uredovora) driving expression of the other zeaxanthin biosynthesis genes. Escherichia coli BL21 (DE3) cells carrying the PTP3-6 plasmid produced 8.3 mg/g dry cell weight astaxanthin, which is 69.4-fold higher than has been previously reported. Using multiple promoter fusions of astaxanthin biosynthesis genes could be applied in other hosts to enhance astaxanthin production. FFAX was identified in recombinant E. coli cells through ultra-performance liquid chromatography-mass spectrometry.

The effect of light-emitting diodes (LEDs) on the production of secondary metabolites in medicinal plants and hairy roots is receiving much attention. The roots and rhizomes of the traditional Chinese medicinal plant Salvia miltiorrhiza Bunge are widely used for treating cardiovascular and cerebrovascular diseases. The main components are liposoluble tanshinones and hydrophilic phenolic acids. Moreover, hairy root culture of S. miltiorrhiza has been used in research of valuable plant-derived secondary metabolites. In this study, we examined the effect of LEDs with different combinations of wavelengths on the content of the main components in hairy roots of S. miltiorrhiza. Tanshinone IIA (TSIIA) content in hairy roots was significantly decreased with all light treatments containing blue light by >60% and was 9 times lower with LED treatment duration changed from 1 week to 3 weeks. HMGR, DXS2, DXR, GGPPS, CPS and CYP76AH1 genes involved in the tanshinone biosynthesis pathway were downregulated by blue light. Furthermore, light quality treatments have different effect on the accumulation of phenolic acids in hairy roots of S. miltiorrhiza. The light treatments 6R3B, 6B3IR, 7RGB and 2R6BUV for 3 weeks could increase rosmarinic acid (RA) content slightly but not salvianolic acid B (SAB) content. Different secondary metabolite contents could be regulated by different wavelength combinations of LEDs. Blue light could reduce TSIIA content in hairy roots of S. miltiorrhiza via gene regulation.

Mungbean (Vigna radiata (L.) Wilczek) is an important rotation legume crop for human nutrition in Asia. Bruchids (Callosobruchus spp.) currently cause heavy damage as pests of grain legumes during storage. We used omics-related technologies to study the mechanisms of bruchid resistance in seeds of the nearly isogenic lines VC1973A (bruchid-susceptible) and VC6089A (bruchid-resistant). A total of 399 differentially expressed genes (DEGs) were identified between the two lines by transcriptome sequencing. Among these DEGs, 251 exhibited high expression levels and 148 expressed low expression levels in seeds of VC6089A. Forty-five differential proteins (DPs) were identified by isobaric tags for relative and absolute quantification (iTRAQ); 21 DPs had higher abundances in VC6089A, and 24 DPs had higher abundances in VC1973A. According to transcriptome and proteome data, only three DEGs/DPs, including resistant-specific protein (g39185), gag/pol polyprotein (g34458), and aspartic proteinase (g5551), were identified and located on chromosomes 5, 1, and 7, respectively. Both g39185 and g34458 genes encode a protein containing a BURP domain. In previous research on bruchid molecular markers, the g39185 gene located close to the molecular markers of major bruchid-resistant locus may be a bruchid-resistant gene.

A novel dehydrin gene (VrDhn1) was isolated from an embryo cDNA library of Vigna radiata (L.) Wilczek (mungbean) variety VC1973A. The intronless VrDhn1 gene encodes a protein belonging to the Y(2)K-type dehydrin family. VrDhn1 protein accumulated in embryos and cotyledons during seed maturation and disappeared 2 days after seed imbibition (DAI). The expression of VrDhn1 mRNA and accumulation of VrDhn1 protein were at high levels in mature seeds, but neither mRNA nor protein was detected in mungbean vegetative tissues under normal growth conditions. The VrDhn1 mRNA level was extremely high in mature seeds and decreased to ∼30% at 1 DAI, and was not detectable at ~7 DAI. Tissue dehydration, salinity and exogenous ABA markedly induced VrDhn1 transcripts in plants as measured by quantitative real-time reverse transcription-PCR (qRT-PCR). VrDhn1 protein was not detected using immunoblots in seedlings under stress treatments. In mature seeds or 1 DAI seedlings, VrDhn1 proteins were immunolocalized in the nucleus and cytoplasm. VrDhn1 exhibited low affinity for non-specific interaction with DNA using electrophoretic mobility shift assays (EMSAs), and the exogenous addition of Zn(2+) or Ni(2+) stimulated interaction. The His-tagged VrDhn1 (30.17 kDa) protein showed a molecular mass of 63.1 kDa on gel filtration, suggesting a dimer form. This is the first report showing that a Y(2)K-type VrDhn1 enters the nucleus and interacts with DNA during seed maturation.

Three novel ethylene response factor (ERF) genes, BkERF1, BkERF2.1 and BkERF2.2, were isolated from a medicinal plant, Bupleurum kaoi. The deduced BkERFs contain a canonical nuclear localization signal and an ERF/AP2 DNA binding domain. RNA gel blot analysis revealed that BkERF1 and BkERF2.1 were ubiquitously expressed at low levels in all parts of mature plants, and that BkERF2.2 was expressed at moderate levels in vegetative tissues. Exogenous application of methyl jasmonate induced BkERF1/2.1/2.2 transcripts. BkERF2.2 transcript levels were slightly increased by addition of ethephon and salicylic acid. BkERFs were localized in the plant nucleus and functioned as transcriptional activators. In B. kaoi cells overexpressing BKERFs, inoculation with Botrytis cinerea increased expression of some defense genes which are associated with enhanced disease resistance. Similarly, overexpression of BkERFs in transgenic Arabidopsis thaliana resulted in elevated mRNA levels of the defense gene PDF1.2, and in enhanced resistance to B. cinerea. Collectively, these results provide evidence that BkERFs mediate the expression of defense-related genes in plants.

Background Mungbean (Vigna radiata [L.] R. Wilczek) is an important legume crop with high nutritional value in South and Southeast Asia. The crop plant is susceptible to a storage pest caused by bruchids (Callosobruchus spp.). Some wild and cultivated mungbean accessions show resistance to bruchids. Genomic and transcriptomic comparison of bruchid-resistant and -susceptible mungbean could reveal bruchid-resistant genes (Br) for this pest and give insights into the bruchid resistance of mungbean. Results Flow cytometry showed that the genome size varied by 61 Mb (mega base pairs) among the tested mungbean accessions. Next generation sequencing followed by de novo assembly of the genome of the bruchid-resistant recombinant inbred line 59 (RIL59) revealed more than 42,000 genes. Transcriptomic comparison of bruchid-resistant and -susceptible parental lines and their offspring identified 91 differentially expressed genes (DEGs) classified into 17 major and 74 minor bruchid-resistance–associated genes. We found 408 nucleotide variations (NVs) between bruchid-resistant and -susceptible lines in regions spanning 2 kb (kilo base pairs) of the promoters of 68 DEGs. Furthermore, 282 NVs were identified on exons of 148 sequence-changed-protein genes (SCPs). DEGs and SCPs comprised genes involved in resistant-related, transposable elements (TEs) and conserved metabolic pathways. A large number of these genes were mapped to a region on chromosome 5. Molecular markers designed for variants of putative bruchid-resistance–associated genes were highly diagnostic for the bruchid-resistant genotype. Conclusions In addition to identifying bruchid-resistance-associated genes, we found that conserved metabolism and TEs may be modifier factors for bruchid resistance of mungbean. The genome sequence of a bruchid-resistant inbred line, candidate genes and sequence variations in promoter regions and exons putatively conditioning resistance as well as markers detecting these variants could be used for development of bruchid-resistant mungbean varieties. Electronic supplementary material The online version of this article (doi:10.1186/s12870-016-0736-1) contains supplementary material, which is available to authorized users.

We performed deep sequencing of the nuclear and organellar genomes of three mungbean genotypes: Vigna radiata ssp. sublobata TC1966, V. radiata var. radiata NM92 and the recombinant inbred line RIL59 derived from a cross between TC1966 and NM92. Moreover, we performed deep sequencing of the RIL59 transcriptome to investigate transcript variability. The mungbean chloroplast genome has a quadripartite structure including a pair of inverted repeats separated by two single copy regions. A total of 213 simple sequence repeats were identified in the chloroplast genomes of NM92 and RIL59; 78 single nucleotide variants and nine indels were discovered in comparing the chloroplast genomes of TC1966 and NM92. Analysis of the mungbean chloroplast transcriptome revealed mRNAs that were affected by transcriptional slippage and RNA editing. Transcriptional slippage frequency was positively correlated with the length of simple sequence repeats of the mungbean chloroplast genome (R2=0.9911). In total, 41 C-to-U editing sites were found in 23 chloroplast genes and in one intergenic spacer. No editing site that swapped U to C was found. A combination of bioinformatics and experimental methods revealed that the plastid-encoded RNA polymerase-transcribed genes psbF and ndhA are affected by transcriptional slippage in mungbean and in main lineages of land plants, including three dicots (Glycine max, Brassica rapa, and Nicotiana tabacum), two monocots (Oryza sativa and Zea mays), two gymnosperms (Pinus taeda and Ginkgo biloba) and one moss (Physcomitrella patens). Transcript analysis of the rps2 gene showed that transcriptional slippage could affect transcripts at single sequence repeat regions with poly-A runs. It showed that transcriptional slippage together with incomplete RNA editing may cause sequence diversity of transcripts in chloroplasts of land plants.

Background Mungbean (Vigna radiata L. Wilczek) is an economically important legume of high nutritional value, however, its cultivation is limited by susceptibility to chilling. Varieties NM94 and VC1973A, with differential susceptibility to stress, serve as good materials for uncovering how they differ in chilling tolerance. This study aimed to identify the ultrastructural, physiological and molecular changes to provide new insights on the differential susceptibility to chilling between varieties VC1973A and NM94. Results Chilling stress caused a greater reduction in relative growth rate, a more significant decrease in maximum photochemical efficiency of PSII and DPPH scavenging activity and more-pronounced ultrastructural changes in VC1973A than in NM94 seedlings. Comparative analyses of transcriptional profiles in NM94 and VC1973A revealed that the higher expression of chilling regulated genes (CORs) in NM94. The transcript levels of lipid transfer protein (LTP), dehydrin (DHN) and plant defensin (PDF) in NM94 seedlings after 72 h at 4 °C was higher than that in its parental lines VC1973A, 6601 and VC2768A. Conclusions Our results suggested that LTP, DHN and PDF may mediate chilling tolerance in NM94 seedlings. Electronic supplementary material The online version of this article (doi:10.1186/s40529-017-0161-2) contains supplementary material, which is available to authorized users.