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Indole-3-acetic acid (IAA) plays an important role in the growth and development of plants. In this study, a series of predominant strains were isolated and identified as Enterobacter sp. with remarkable IAA-producing capabilities. The IAA-producing strains are mainly tryptophan-dependent and have significantly high yields of IAA (3477 μg mL−1 and 3378 μg mL−1). The ipdC gene encoding indole-3-pyruvate decarboxylase was identified by genomic analysis and RT-qPCR analysis, indicating the involvement of the indole-3-pyruvic acid (IPyA) pathway of IAA biosynthesis. The IPyA pathway was also confirmed by the intermediate assay. The IAA product of microbial metabolites was isolated, purified and characterized. These microbes exhibiting IAA production significantly promoted the growth of maize, increasing root length, plant height, fresh weight and dry weight. Thus, Enterobacter sp. with high IAA production has great prospects in agricultural and industrial applications.

Tanshinones are major secondary metabolites in Salvia miltiorrhiza Bunge, the traditional Chinese medicinal plant Danshen. Increasing the production of tanshinones is important because of their significant economic value in human medicine, for the treatment of cardiovascular and cerebrovascular diseases and for their anti-tumor properties. Phosphate (Pi) starvation can change secondary metabolism in plants. MYB transcription factors (TFs) have been reported to be involved in both Pi starvation signaling and secondary metabolism regulation, enabling plants to build a relationship between the Pi starvation signal and secondary metabolism. In the present study, a nucleus-located R2R3 MYB TF, SmMYB98b, was found in S. militorrhiza. SmMYB98b was shown to belong to subgroup 20 of R2R3-MYB TFs, and expression could be induced by low-Pi conditions. The overexpression of SmMYB98b in S. militorrhiza hairy roots stimulated tanshinone accumulation. Plants overexpressing SmMYB98b exhibited Pi-starvation responses, such as decreased Pi concentration and activation of genes inducible by phosphate starvation, whereas transgenic plants with the SmMYB98b-RNA interference (RNAi) construct showed the opposite phenotype. In summary, the present study highlighted the role of SmMYB98b as a regulator of tanshinone biosynthesis and its potential function in Pi-starvation signaling. These results might have wider implications for studying the crosstalk between Pi stress responses and secondary metabolism pathways in plants. This study highlights the role of SmMYB98b as a positive regulator of tanshinone biosynthesis and its potential function in Pi-starvation signaling in Salvia miltiorrhiza.

L-Phosphinotricin (L-PPT) is an active compound of a broad-spectrum herbicide used worldwide. Asymmetric synthesis of L-PPT from 4-(hydroxy(methyl)phosphoryl)-2-oxobutanoic acid (PPO) using transaminase is of great significance due to the 100% theoretical yield and high enantioselectivity. In this study, a new transaminase from Pseudomonas fluorescens ZJB09-108 (named as Pf-TA) was cloned and expressed in E. coli BL21 (DE3). The amino acid sequence analysis showed that the maximum sequence identity of Pf-TA with other transaminases is 74%. This recombinant Pf-TA exhibited a good temperature stability and pH stability. The Km and kcat of Pf-TA toward PPO were 34.02 mmol L−1 and 11.3 s−1, respectively. After optimization of the L-PPT biosynthesis catalyzed by whole-cells of E. coli harboring transaminase, >99% yield of L-PPT with 99.9% of enantiomeric excess was attained at a PPO concentration of 100 mM. High yield of L-PPT (79%) with 99.9% enantiomeric excess was achieved at high PPO concentration of 500 mM as well. These results suggested the recombinant transaminase is a potential candidate for the biosynthesis of L-PPT from PPO.

Background Isobutanol is considered a potential biofuel, thanks to its high-energy content and octane value, limited water solubility, and compatibility with gasoline. As its biosynthesis pathway is known, a microorganism, such as Saccharomyces cerevisiae, that inherently produces isobutanol, can serve as a good engineering host. Isobutanol’s toxicity, however, is a major obstacle for bioproduction. This study is to understand how yeast tolerates isobutanol. Results A S. cerevisiae gene-deletion library with 5006 mutants was used to screen genes related to isobutanol tolerance. Image recognition was efficiently used for high-throughput screening via colony size on solid media. In enrichment analysis of the 161 isobutanol-sensitive clones identified, more genes than expected were mapped to tryptophan biosynthesis, ubiquitination, and the pentose phosphate pathway (PPP). Interestingly, adding exogenous tryptophan enabled both tryptophan biosynthesis and PPP mutant strains to overcome the stress. In transcriptomic analysis, cluster analysis of differentially expressed genes revealed the relationship between tryptophan and isobutanol stress through some specific cellular functions, such as biosynthesis and transportation of amino acids, PPP, tryptophan metabolism, nicotinate/nicotinamide metabolism (e.g., nicotinamide adenine dinucleotide biosynthesis), and fatty acid metabolism. Conclusions The importance of tryptophan in yeast’s tolerance to isobutanol was confirmed by the recovery of isobutanol tolerance in defective strains by adding exogenous tryptophan to the growth medium. Transcriptomic analysis showed that amino acid biosynthesis- and transportation-related genes in a tryptophan biosynthesis-defective host were up-regulated under conditions similar to nitrogen starvation. This may explain why ubiquitination was required for the protein turnover. PPP metabolites may serve as precursors and cofactors in tryptophan biosynthesis to enhance isobutanol tolerance. Furthermore, the tolerance mechanism may also be linked to tryptophan downstream metabolism, including the kynurenine pathway and nicotinamide adenine dinucleotide biosynthesis. Both pathways are responsible for cellular redox balance and anti-oxidative ability. Our study highlights the central role of tryptophan in yeast’s isobutanol tolerance and offers new clues for engineering a yeast host with strong isobutanol tolerance.

Dendrobium officinale is a kind of traditional Chinese herbal medicine. Its flowers could be used as health care tea for its aroma flavor and medicinal value. Most recent studies demonstrated that terpenoids are the main components of the aromatic compounds in the flowers, but the biosynthesis of terpenoids is poorly understood in D. officinale. In the experiment, the flowers from two cultivars of D. officinale with different smells were collected. The transcriptome analysis and combined volatile terpenoids determination were performed to identify the genes related to the biosynthesis of the terpenoids. The results showed that the different products of volatile terpenoids are α-thujene, linalool, α-terpineol, α-phellandrene, γ-muurolene, α-patchoulene, and δ-elemene in two cultivar flowers. The transcriptome analysis detected 25,484 genes in the flowers. And 18,650 differentially expressed genes were identified between the two cultivars. Of these genes, 253 genes were mapped to the terpenoid metabolism pathway. Among these genes, 13 terpene synthase (TPS) genes may have correlations with AP2/ERF, WRKY, MYB, bHLH, and bZIP transcription factors by weighted gene co-expression network analysis (WGCNA). The transcription factors have regulatory effects on TPS genes. These results may provide ideas for the terpenoid biosynthesis and regulatory network of D. officinale flowers.

SmbHLH148 activated the whole biosynthetic pathways of phenolic acids and tanshinones, thus upregulated the production of both the two groups of pharmaceutical ingredients in Salvia miltiorrhiza. Phenolic acids and tanshinones are the two important groups of pharmaceutical ingredients presented in Salvia miltiorrhiza Bunge. The bHLH transcription factors could regulate secondary metabolism efficiently in plants. However, there are only some MYCs have been studied on regulation of either phenolic acids or tanshinones biosynthesis. In this study, a bHLH TF named SmbHLH148, which is homologous to AtbHLH148, AtbHLH147 and CubHLH1, was isolated and functionally characterized from S. miltiorrhiza. Transcription of SmbHLH148 could be intensely induced by ABA and also be moderately induced by MeJA and GA. SmbHLH148 is present in all the six tissues and mostly expressed in fibrous root and flowers. Subcellular localization analysis found that SmbHLH148 was localized in the nucleus. Overexpression of SmbHLH148 significantly increased not only three phenolic acids components accumulation but also three tanshinones content. Content of caffeic acid, rosmarinic acid and salvianolic acid B were reached to 2.87-, 4.00- and 5.99-fold of the control in the ObHLH148-3, respectively. Content of dihydrotanshinone I, cryptotanshinone, and tanshinone I were also present highest in ObHLH148-3, reached 2.5-, 5.04- and 3.97-fold of the control, respectively. Expression analysis of pathway genes of phenolic acids and tanshinones in transgenic lines showed that most of them were obviously upregulated. Moreover, transcription of AREB and JAZs were also induced in SmbHLH148 overexpression lines. These results suggested that SmbHLH148 might be taken part in ABA and MeJA signaling and activated almost the whole biosynthetic pathways of phenolic acids and tanshinones, thus the production of phenolic acids and tanshinones were upregulated.

Phenolic acids and tanshinones are two groups of pharmaceutical components present in Salvia miltiorrhiza Bunge. Methyl jasmonate (MeJA) has been reported to influence the accumulation of both phenolic acids and tanshinones in S. miltiorrhiza hairy roots. However, there is currently a lack of information regarding the comparison of how these two groups of bioactive compounds in S. miltiorrhiza respond to MeJA under the same conditions. In the present study, the effect of 100 µM MeJA on the biosynthesis of phenolic acids and tanshinones in S. miltiorrhiza hairy roots was investigated. The results showed that MeJA dramatically induced the accumulation of five different phenolic acids, especially rosmarinic acid and salvianolic acid B, which reached their highest contents at day 3 (20.3 mg/g DW, 1.5-fold of control) and day 6 (47.49 mg/g DW, 2.5-fold of control), respectively. The total production of phenolic acids was induced by as much as 3.3-fold of the control (day 9 after treatment), reaching 357.5 mg/L at day 6. However, tanshinone I was almost unaffected by MeJA treatment, and the accumulation of tanshinone IIA was inhibited. Furthermore, cryptotanshinone and dihydrotanshinone I were moderately induced by MeJA. The gene expression results indicated that MeJA probably induced the whole pathways, especially the tyrosine-derived pathway and the methylerythritol phosphate pathway, and finally resulted in the increased production of these metabolites. This study will help us to further understand how the different biosynthetic mechanisms of phenolic acids and tanshinones respond to MeJA and provide a reference for the future selection of elicitors for application to improving the production of targeted compounds.

Background Drought stress during grain development causes significant yield loss in cereal production. The phosphorylated modification of starch granule-binding proteins (SGBPs) is an important mechanism regulating wheat starch biosynthesis. In this study, we performed the first proteomics and phosphoproteomics analyses of SGBPs in elite Chinese bread wheat (Triticum aestivum L.) cultivar Jingdong 17 under well-watered and water-stress conditions. Results Water stress treatment caused significant reductions in spike grain numbers and weight, total starch and amylopectin content, and grain yield. Two-dimensional gel electrophoresis revealed that the quantity of SGBPs was reduced significantly by water-deficit treatment. Phosphoproteome characterization of SGBPs under water-deficit treatment demonstrated a reduced level of phosphorylation of main starch synthesis enzymes, particularly for granule-bound starch synthase (GBSS I), starch synthase II-a (SS II-a), and starch synthase III (SS III). Specifically, the Ser34 site of the GBSSI protein, the Tyr358 site of SS II-a, and the Ser837 site of SS III-a exhibited significant less phosphorylation under water-deficit treatment than well-watered treatment. Furthermore, the expression levels of several key genes related with starch biosynthesis detected by qRT-PCR were decreased significantly at 15 days post-anthesis under water-deficit treatment. Immunolocalization showed a clear movement of GBSS I from the periphery to the interior of starch granules during grain development, under both water-deficit and well-watered conditions. Conclusions Our results demonstrated that the reduction in gene expression or transcription level, protein expression and phosphorylation levels of starch biosynthesis related enzymes under water-deficit conditions is responsible for the significant decrease in total starch content and grain yield. Electronic supplementary material The online version of this article (10.1186/s12870-017-1118-z) contains supplementary material, which is available to authorized users.

Phosphate starvation increased the production of phenolic acids by inducing the key enzyme genes in a positive feedback pathway in Saliva miltiorrhiza hairy roots. SPX may be involved in this process. Salvia miltiorrhiza is a wildly popular traditional Chinese medicine used for the treatment of coronary heart diseases and inflammation. Phosphate is an essential plant macronutrient that is often deficient, thereby limiting crop yield. In this study, we investigated the effects of phosphate concentration on the biomass and accumulation of phenolic acid in S. miltiorrhiza. Results show that 0.124 mM phosphate was favorable for plant growth. Moreover, 0.0124 mM phosphate was beneficial for the accumulation of phenolic acids, wherein the contents of danshensu, caffeic acid, rosmarinic acid, and salvianolic acid B were, respectively, 2.33-, 1.02-, 1.68-, and 2.17-fold higher than that of the control. By contrast, 12.4 mM phosphate inhibited the accumulation of phenolic acids. The key enzyme genes in the phenolic acid biosynthesis pathway were investigated to elucidate the mechanism of phosphate starvation-induced increase of phenolic acids. The results suggest that phosphate starvation induced the gene expression from the downstream pathway to the upstream pathway, i.e., a feedback phenomenon. In addition, phosphate starvation response gene SPX (SYG1, Pho81, and XPR1) was promoted by phosphate deficiency (0.0124 mM). We inferred that SPX responded to phosphate starvation, which then affected the expression of later responsive key enzyme genes in phenolic acid biosynthesis, resulting in the accumulation of phenolic acids. Our findings provide a resource-saving and environmental protection strategy to increase the yield of active substance in herbal preparations. The relationship between SPX and key enzyme genes and the role they play in phenolic acid biosynthesis during phosphate deficiency need further studies.

Pistacia chinensis Bunge is a bioenergy tree whose seed oil has been proposed as a promising feedstock for both edible and industrial oil that can be used for biodiesel production in China. However, the transcriptomic information available for P. chinensis and the genes involved in biosynthesis of oil remain largely unknown. We used Illumina RNA-sequencing technology to sequence the complete transcriptome of P. chinensis for the first time. Over 56 million high-quality reads (5.27 Gb total) were obtained and assembled into 127,545 unigenes with a total length of 89.65 Mb and an average length of 703 bp. Among the unigenes identified, 265 were potentially involved in oil biosynthesis, including FA biosynthesis (71 unigenes), elongation (54 unigenes), desaturation (38 unigenes); triacylglycerol (TAG) and oil body (OB) biosynthesis (65 unigenes); and regulation of acyl editing during TAG biosynthesis (six unigenes). Furthermore, 31 unigenes encoding six activators and five inhibitors of TFs were associated with oil biosynthesis. Expression pattern of two desaturase enzymes were analyzed by quantitative real-time PCR (qRT-PCR) in five tissues of P. chinensis, the results shown seeds had the highest expression level. This study is the first to characterize the P. chinensis transcriptome and sequence information of those genes that are involved in oil biosynthesis could be used for metabolic engineering of pistacia to accelerate the breeding of new tree strains with better agronomic oil yields.

Tuberculosis is a major global health problem, and the emergence of multidrug-resistant and extensively drug-resistant strains has increased the difficulty of treating this disease. Among the novel antituberculosis drugs in the pipeline, decaprenylphosphoryl-beta- d -ribose-2-epimerase (DprE1) inhibitors such as BTZ043 and pBTZ169 exhibited extraordinary antituberculosis potency. Here, the metabolites of the new DprE1 inhibitor SKLB-TB1001 in vivo and its inhibition of cytochrome P450 isoforms and plasma protein binding (PPB) in vitro were studied. The results showed that rapid transformation and high PPB resulted in inadequate exposure in vivo and thus led to the moderate potency of SKLB-TB1001 in vivo . This study provided explanations for the discrepant potency of this scaffold in vivo and in vitro . Meanwhile, it also provides a rationale for lead optimization of this very promising scaffold of antituberculosis agents to prevent them from being metabolized, thus improving their exposure in vivo .

The adaptations that protect pathogenic microorganisms against the cytotoxicity of nitric oxide (NO) engendered in the immune response are incompletely understood. We show here that salmonellae experiencing nitrosative stress suffer dramatic losses of the nucleoside triphosphates ATP, GTP, CTP, and UTP while simultaneously generating a massive burst of the alarmone nucleotide guanosine tetraphosphate. RelA proteins associated with ribosomes overwhelmingly synthesize guanosine tetraphosphate in response to NO as a feedback mechanism to transient branched-chain amino acid auxotrophies. Guanosine tetraphosphate activates the transcription of valine biosynthetic genes, thereby reestablishing branched-chain amino acid biosynthesis that enables the translation of the NO-consuming flavohemoglobin Hmp. Guanosine tetraphosphate synthesized by RelA protects salmonellae from the metabolic stress inflicted by reactive nitrogen species generated in the mammalian host response. This research illustrates the importance of nucleotide metabolism in the adaptation of salmonellae to the nutritional stress imposed by NO released in the innate host response., IMPORTANCE Nitric oxide triggers dramatic drops in nucleoside triphosphates, the building blocks that power DNA replication; RNA transcription; translation; cell division; and the biosynthesis of fatty acids, lipopolysaccharide, and peptidoglycan. Concomitantly, this diatomic gas stimulates a burst of guanosine tetraphosphate. Global changes in nucleotide metabolism may contribute to the potent bacteriostatic activity of nitric oxide. In addition to inhibiting numerous growth-dependent processes, guanosine tetraphosphate positively regulates the transcription of branched-chain amino acid biosynthesis genes, thereby facilitating the translation of antinitrosative defenses that mediate recovery from nitrosative stress.

Waxy starch has an important influence on the qualities of breads. Generally, grain weight and yield in waxy wheat (Triticum aestivum L.) are significantly lower than in bread wheat. In this study, we performed the first proteomic and phosphoproteomic analyses of starch granule-binding proteins by comparing the waxy wheat cultivar Shannong 119 and the bread wheat cultivar Nongda 5181. These results indicate that reduced amylose content does not affect amylopectin synthesis, but it causes significant reduction of total starch biosynthesis, grain size, weight and grain yield. Two-dimensional differential in-gel electrophoresis identified 40 differentially expressed protein (DEP) spots in waxy and non-waxy wheats, which belonged mainly to starch synthase (SS) I, SS IIa and granule-bound SS I. Most DEPs involved in amylopectin synthesis showed a similar expression pattern during grain development, suggesting relatively independent amylose and amylopectin synthesis pathways. Phosphoproteome analysis of starch granule-binding proteins, using TiO2 microcolumns and LC-MS/MS, showed that the total number of phosphoproteins and their phosphorylation levels in ND5181 were significantly higher than in SN119, but proteins controlling amylopectin synthesis had similar phosphorylation levels. Our results revealed the lack of amylose did not affect the expression and phosphorylation of the starch granule-binding proteins involved in amylopectin biosynthesis.

The synthesis of nanoparticles from biological processes is evolving a new era of research interests in nanotechnology. Silver nanoparticles are usually synthesized by chemicals which are quite toxic and ∞ammable in nature. This study deals with an environment friendly and biosynthesis process of antibacterial silver nanoparticles using bamboo leaves. The formation and characterisation of AgNPs were conflrmed by UV-Vis spectroscopy, energy-dispersive spectroscopy (EDX), X-ray difiraction (XRD) and transmission electron microscope (TEM). The antimicrobial activities were carried out against E. coli and S. aureus strains by using disc difiusion method.

We found herein that the intracytoplasmic pool of the low-molecular weight (LMW) thiol glutathione (GSH) is readily oxidized in Salmonella exposed to nitric oxide (NO). The hypersusceptibility of gshA and gshB mutants lacking γ-glutamylcysteine and glutathione synthetases to NO and S-nitrosoglutathione indicates that GSH antagonizes the bacteriostatic activity of reactive nitrogen species. Metabolites of the GSH biosynthetic pathway do not affect the enzymatic activity of classical NO targets such as quinol oxidases. In contrast, LMW thiols diminish the nitrosative stress experienced by enzymes, such as glutamine oxoglutarate amidotransferase, that contain redox active cysteines. LMW thiols also preserve the transcription of Salmonella pathogenicity island 2 gene targets from the inhibitory activity of nitrogen oxides. These findings are consistent with the idea that GSH scavenges reactive nitrogen species (RNS) other than NO. Compared to the adaptive response afforded by inducible systems such as the hmp-encoded flavohemoprotein, gshA, encoding the first step of GSH biosynthesis, is constitutively expressed in Salmonella. An acute model of salmonellosis has revealed that the antioxidant and antinitrosative properties associated with the GSH biosynthetic pathway represent a first line of Salmonella resistance against reactive oxygen and nitrogen species engendered in the context of a functional NRAMP1R divalent metal transporter.

GDP-D-mannose pyrophosphorylase catalyzes the production of GDP-D-mannose, an intermediate product in the plant ascorbic acid (AsA) biosynthetic pathway. This enzyme is a key regulatory target in AsA biosynthesis and is encoded byVITAMIN C DEFECTIVE 1(VTC1) in theArabidopsis thalianagenome. Here, recombinant VTC1 was expressed, purified and crystallized. Diffraction data were obtained from VTC1 crystals grown in the absence and presence of substrate using X-rays. The ligand-free VTC1 crystal diffracted X-rays to 3.3 Å resolution and belonged to space groupR32, with unit-cell parametersa=b= 183.6,c= 368.5 Å, α = β = 90, γ = 120°; the crystal of VTC1 in the presence of substrate diffracted X-rays to 1.75 Å resolution and belonged to space groupP21, with unit-cell parametersa= 70.8,b= 83.9,c= 74.5 Å, α = γ = 90.0, β = 114.9°.

Lysine acetylation is a major post-translational modification that plays an important regulatory role in almost every aspects in both eukaryotes and prokaryotes. Bacillus amyloliquefaciens, a Gram-positive bacterium, is very effective for the control of plant pathogens. However, very little is known about the function of lysine acetylation in this organism. Here, we conducted the first lysine acetylome in B. amyloliquefaciens through a combination of highly sensitive immune-affinity purification and high-resolution LC−MS/MS. Overall, we identified 3268 lysine acetylation sites in 1254 proteins, which account for 32.9% of the total proteins in this bacterium. Till date, this is the highest ratio of acetylated proteins that have been identified in bacteria. Acetylated proteins are associated with a variety of biological processes and a large fraction of these proteins are involved in metabolism. Interestingly, for the first time, we found that about 71.1% (27/38) and 78.6% (22/28) of all the proteins tightly related to the synthesis of three types of pepketides and five families of lipopeptides were acetylated, respectively. These findings suggest that lysine acetylation plays a critical role in the regulation of antibiotics biosynthesis. These data serves as an important resource for further elucidation of the physiological role of lysine acetylation in B. amyloliquefaciens.

When cells of Lithospermum erythrorhizon were transferred from B5 solid medium into M9 liquid medium and grown in the dark, they produced and accumulated shikonin and its derivatives; meanwhile, transcripts of PAL, 4CL, HMGR, PGT, and CYP98A6 were rapidly induced within 2 h, peaking within 6 h, and then decreasing over time. However, when L. erythrorhizon cells were cultured in M9 medium and grown under white light, a negative regulator for the biosynthesis of shikonin and its derivatives, the “stimulating effect” of the medium transition on the transcription of these genes was also displayed with similar patterns over 24 h of culture period. To investigate the time-dependent effect of light signals on regulating gene transcription, expression analysis of L. erythrorhizon dark-inducible genes LeDI-1–LeDI-5 was conducted. No obvious inhibitory effects of light signals on the transcription of LeDI-1–LeDI-5 were detected during the first 12 h, but these genes, in particular LeDI-2 and LeDI-4, were suppressed by light signals to some degree during longer culture periods, 12 h to 10 days. These findings suggest that light signals are likely to inhibit the transcription of the shikonin-biosynthetic genes indirectly or under long-term conditions.

Growth of Cryptococcus neoformans was inhibited by nine nitrogen and sulfur-containing sterols with a heteroatom positioned at C3, C7, C24, C25 or C32 in the lanostane frame. Analysis of the sterol composition of control and treated cells by GC-MS and (1)H NMR has proven that the C-methylation reaction catalyzed by the sterol 24-C-methyltransferase (24-SMT) is the crucial first step in a kinetically favored pathway that fails to include obtusifoliol or zymosterol as intermediates. Cultures fed [methyl-(2)H(3)]methionine led to two deuterium atoms into each of the newly biosynthesized sterols forming a route lanosterol, eburicol (24(28)-methylene-24,25-dihydrolanosterol), 32-noreburicol and ergost-7-enol to ergosterol. Examination of the substrate specificity of a soluble 24-SMT from C. neoformans showed lanosterol to be the optimal acceptor molecule. Incubation with the test compounds generated induced amounts of lanosterol, eburicol or 32-noreburicol concurrent with a decrease of ergosterol. Among them 24(R,S),25-epiminolanosterol (inhibitor of 24-SMT) showed the most potent in vitro antifungal activity comparable to those of itraconazole (inhibitor of the 14-demethylase). Taken together, these data indicate that treatment with substrate-based inhibitors of 24-SMT, a catalyst not found in humans, can disrupt ergosterol homeostasis involved with fungal growth and therefore these compounds can provide leads for rational drug design of opportunistic pathogens.

The tetratricopeptide repeat (TPR)-containing protein FLU is a negative regulator of chlorophyll biosynthesis in plants. It directly interacts through its TPR domain with glutamyl-tRNA reductase (GluTR), the rate-limiting enzyme in the formation of δ-aminolevulinic acid (ALA). Delineation of how FLU binds to GluTR is important for understanding the molecular basis for FLU-mediated repression of synthesis of ALA, the universal tetrapyrrole precursor. Here, we characterize the FLU-GluTR interaction by solving the crystal structures of the uncomplexed TPR domain of FLU (FLU(TPR)) at 1.45-A resolution and the complex of the dimeric domain of GluTR bound to FLU(TPR) at 2.4-A resolution. Three non-canonical TPR motifs of each FLU(TPR) form a concave surface and clamp the helix bundle in the C-terminal dimeric domain of GluTR. We demonstrate that a 2:2 FLU(TPR)-GluTR complex is the functional unit for FLU-mediated GluTR regulation and suggest that the formation of the FLU-GluTR complex prevents glutamyl-tRNA, the GluTR substrate, from binding with this enzyme. These results also provide insights into the spatial regulation of ALA synthesis by the membrane-located FLU protein.

The algal β-carotene hydroxylase gene Crchyb from Chlamydomonas reinhardtii, Czchyb from Chlorella zofingiensis, or Hpchyb from Haematococcus pluvialis and six other carotenoid-synthesis pathway genes were co-integrated into the genome of a yeast host. Each of these three algal genes showed a higher efficiency to convert β-carotene to downstream carotenoids than the fungal genes from Phaffia rhodozyma. Furthermore, the strain with Hpchyb displayed a higher carotenoid productivity than the strains integrated with Crchyb or Czchyb, indicating that Hpchyb is more efficient than Crchyb and Czchyb. These results suggest that β-carotene hydroxylase plays a crucial role in the biosynthesis of carotenoids.

To explore the mode of the spatio-temporal expression of six newly discovered ginsenoside biosynthesis candidate gene transcripts, both Northern blotting and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) were used to elucidate the mRNA expression levels of the transcripts in various tissues and organs of Panax ginseng C. A. Meyer during different growth development stages. The six gene transcripts were all differentially expressed in cultured callus, root, stem, leaf, and seed. The mRNA expression levels were significantly higher in four-year-old roots than in one-year-old roots, and results of semi-quantitative RT-PCR assays were in accordance with those of Northern blotting analyses. The results strongly suggest that all six genes were differentially expressed at root-specific developmental stages. In particular, when a quiescent early stage culture suspension of P. ginseng cells was exposed to the ginsenoside biosynthesis-promoting elicitor Aspergillus niger polysaccharide, the GBR6 gene transcript response showed time-dependent increments and was parallel with ginsenoside productivity (P < 0.01). Overexpressionof the GBR6 gene is likely to play a critically important role in the biosynthesis of ginsenosides. The results of the present study provided a background for the further elucidation of the structure and physiological function of these six candidate genes. (Managing editor: Wei WANG)

A series of new 4″-O-carbamates of 11,12-cyclic carbonate erythromycin A 6,9-imino ether were synthesized and evaluated for their in vitro antibacterial activity. All the desired compounds demonstrated favorable activity (0.03 μg ml(-1)) against erythromycin-susceptible Streptococcus pneumoniae comparable to the references, exhibiting 133-fold higher activity than precursor 2 or 3. Similarly, all of the analogs exhibited improved activity against the erythromycin-resistant S. pneumoniae encoded by the erm gene and the erm and mef genes, showing 4-32-fold more effectiveness than erythromycin A.

Background Lysine acetylation in proteins is a ubiquitous and conserved post-translational modification, playing a critical regulatory role in almost every aspect of living cells. Although known for many years, its function remains elusive in Fusarium graminearum, one of the most important necrotrophic plant pathogens with huge economic impact. Results By the combination of affinity enrichment and high-resolution LC-MS/MS analysis, large-scale lysine acetylome analysis was performed. In total, 577 lysine acetylation sites matched to 364 different proteins were identified. Bioinformatics analysis of the acetylome showed that the acetylated proteins are involved in a wide range of cellular functions and exhibit diverse subcellular localizations. Remarkably, 10 proteins involved in the virulence or DON (deoxynivalenol) biosynthesis were found to be acetylated, including 4 transcription factors, 4 protein kinases and 2 phosphatases. Protein-protein interaction network analysis revealed that acetylated protein complexes are involved in diversified interactions. Conclusions This work provides the first comprehensive survey of a possible lysine acetylome in F. graminearum and reveals previously unappreciated roles of lysine acetylation in the regulation of diverse biological processes. This work provides a resource for functional analysis of acetylated proteins in filamentous fungi. Electronic supplementary material The online version of this article (doi:10.1186/s12864-016-3361-3) contains supplementary material, which is available to authorized users.