Farnesol-mediated shift in the metabolic origin of prenyl groups used for protein prenylation in plants

Methyl-Jasmonate Functions as a Molecular Switch Promoting Cross-Talk between Pathways for the Biosynthesis of Isoprenoid Backbones Used to Modify Proteins in Plants

In plants, the plastidial mevalonate (MVA)-independent pathway is required for the modification with geranylgeranyl groups of CaaL-motif proteins, which are substrates of protein geranylgeranyltransferase type-I (PGGT-I). As a consequence, fosmidomycin, a specific inhibitor of 1-deoxy-d-xylulose (DX)-5 phosphate reductoisomerase/DXR, the second enzyme in this so-called methylerythritol phosphate (MEP) pathway, also acts as an effective inhibitor of protein prenylation. This can be visualized in plant cells by confocal microscopy by expressing GFP-CaM-CVIL, a prenylation sensor protein. After treatment with fosmidomycin, the plasma membrane localization of this GFP-based sensor is altered, and a nuclear distribution of fluorescence is observed instead. In tobacco cells, a visual screen of conditions allowing membrane localization in the presence of fosmidomycin identified jasmonic acid methyl esther (MeJA) as a chemical capable of gradually overcoming inhibition. Using Arabidopsis protein prenyltransferase loss-of-function mutant lines expressing GFP-CaM-CVIL proteins, we demonstrated that in the presence of MeJA, protein farnesyltransferase (PFT) can modify the GFP-CaM-CVIL sensor, a substrate the enzyme does not recognize under standard conditions. Similar to MeJA, farnesol and MVA also alter the protein substrate specificity of PFT, whereas DX and geranylgeraniol have limited or no effect. Our data suggest that MeJA adjusts the protein substrate specificity of PFT by promoting a metabolic cross-talk directing the origin of the prenyl group used to modify the protein. MVA, or an MVA-derived metabolite, appears to be a key metabolic intermediate for this change in substrate specificity.

Recovery and utilization of waste filtrate from industrial biological fermentation: Development and metabolite profile of the Bacillus cereus liquid bio-fertilizer

Most fermentation waste filtrates can be used as raw materials for producing bio-fertilizers to reduce wastewater emissions and environmental pollution, but their bio-fertilizer utilization depends on the nutrients contained and their metabolized by functional microorganism. To achieve bio-fertilizer utilization of Acremonium terricola fermented waste filtrate, this study systematically explored the functional microbial species for making good use of waste liquid, optimized material process parameters for bio-fertilizer production based on D-optimal mixture design method, and analyzed the composition of the waste filtrate and its metabolism by functional microorganisms using a non-targeted LC-MS metagenomics technique. The results showed that Bacillus cereus was the functional microbial candidate for producing bio-fertilizer because of its more efficiently utilize the waste filtrate than other Bacillus sp. The optimal material process parameters of the liquid bio-fertilizer were the inoculum dose of 5% (v:v, %), 80% of waste filtrate, 0.25% of N, 3.5% of P2O5, 3.25% of K2O of mass percentage. Under these conditions, the colony forming unit (CFU) of Bacillus cereus could reach (1.59 ± 0.01) × 108 CFU/mL, which met the bio-fertilizer standard requirements of the People's Republic of China (NY/T798). Furthermore, the potential functions of bio-fertilizer were studied based on comparison of raw materials and production components: on the one hand, waste filtrate contained abundant of nitrogen and carbon sources, and bioactive substances secreted by Acremonium terricola, such as β-alanyl-L-lysine, anserine, UMP, L-lactic acid and etc., which could meet the nutrient requirements of the growth of Bacillus cereus; On the other hand, some compounds of waste filtrate with the potential to benefit the plant growth and defense, such as betaine aldehyde, (2E,6E)-farnesol, homogentisic acid and etc., were significantly up regulated by Bacillus cereus utilization of the filtrate. To sum up, this work highlighted that the waste filtrate could be efficiently developed into liquid bio-fertilizer by Bacillus cereus.

Engineering Nicotiana tabacum trichomes for triterpenic acid production

In this work, we aimed at implementing the biosynthesis of triterpenic acids in Nicotiana tabacum glandular trichomes. Although endogenous genes coding for enzymes involved in such biosynthetic pathway are found in the Nicotiana tabacum genome, implementing such pathway specifically in glandular trichomes required to boost endogenous enzymatic activities. Five transgenes coding for a farnesyl-diphosphate synthase, a squalene synthase, a squalene epoxidase, a beta-amyrin synthase and a beta-amyrin 28-monooxygenase were introduced in N.tabacum, their expression being driven by pMALD1, a trichome-specific transcriptional promoter. This study aimed at testing whether sinking isoprenoid precursors localized in plastids, by exploiting potential cross-talks allowing the exchange of terpenoid pools from the chloroplast to the cytosol, could be a way to improve overall yield. By analyzing metabolites extracted from entire leaves, a low amount of ursolic acid was detected in plants expressing the five transgenes. Our study shows that the terpene biosynthetic pathway could be, in part, redirected in N.tabacum glandular trichomes with no deleterious phenotype at the whole plant level (chlorosis, dwarfism,…). In light of our results, possible ways to improve the final yield are discussed.

The Biomedical Importance of the Missing Pathway for Farnesol and Geranylgeraniol Salvage

Isoprenoids are the output of the polymerization of five-carbon, branched isoprenic chains derived from isopentenyl pyrophosphate (IPP) and its isomer, dimethylallyl pyrophosphate (DMAPP). Isoprene units are consecutively condensed to form longer structures such as farnesyl and geranylgeranyl pyrophosphate (FPP and GGPP, respectively), necessary for the biosynthesis of several metabolites. Polyprenyl transferases and synthases use polyprenyl pyrophosphates as their natural substrates; however, it is known that free polyprenols, such as farnesol (FOH), and geranylgeraniol (GGOH) can be incorporated into prenylated proteins, ubiquinone, cholesterol, and dolichols. Furthermore, FOH and GGOH have been shown to block the effects of isoprenoid biosynthesis inhibitors such as fosmidomycin, bisphosphonates, or statins in several organisms. This phenomenon is the consequence of a short pathway, which was observed for the first time more than 25 years ago: the polyprenol salvage pathway, which works via the phosphorylation of FOH and GGOH. Biochemical studies in bacteria, animals, and plants suggest that this pathway can be carried out by two enzymes: a polyprenol kinase and a polyprenyl-phosphate kinase. However, to date, only a few genes have been unequivocally identified to encode these enzymes in photosynthetic organisms. Nevertheless, pieces of evidence for the importance of this pathway abound in studies related to infectious diseases, cancer, dyslipidemias, and nutrition, and to the mitigation of the secondary effects of several drugs. Furthermore, nowadays it is known that both FOH and GGOH can be incorporated via dietary sources that produce various biological effects. This review presents, in a simplified but comprehensive manner, the most important data on the FOH and GGOH salvage pathway, stressing its biomedical importance The main objective of this review is to bring to light the need to discover and characterize the kinases associated with the isoprenoid salvage pathway in animals and pathogens.

The specific molecular architecture of plant 3-hydroxy-3-methylglutaryl-CoA lyase

3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase (HMGL) is involved in branched-chain amino acid catabolism leading to acetyl-CoA production. Here, using bioinformatics analyses and protein sequence alignments, we found that in Arabidopsis thaliana a single gene encodes two HMGL isoforms differing in size (51 kDa, HMGL51 and 46 kDa, HMGL46). Similar to animal HMGLs, both isoforms comprised a C-terminal type 1 peroxisomal retention motif, and HMGL51 contained a mitochondrial leader peptide. We observed that only a shortened HMGL (35 kDa, HMGL35) is conserved across all kingdoms of life. Most notably, all plant HMGLs also contained a specific N-terminal extension (P100) that is located between the N-terminal mitochondrial targeting sequence TP35 and HMGL35 and is absent in bacteria and other eukaryotes. Interestingly, using HMGL enzyme assays, we found that rather than HMGL46, homodimeric recombinant HMGL35 is the active enzyme catalyzing acetyl-CoA and acetoacetate synthesis when incubated with (S)-HMG-CoA. This suggested that the plant-specific P100 peptide may inactivate HMGL according to specific physiological requirements. Therefore, we investigated whether the P100 peptide in HMGL46 alters its activity, possibly by modifying the HMGL46 structure. We found that induced expression of a cytosolic HMGL35 version in A. thaliana delays germination and leads to rapid wilting and chlorosis in mature plants. Our results suggest that in plants, P100-mediated HMGL inactivation outside of peroxisomes or mitochondria is crucial, protecting against potentially cytotoxic effects of HMGL activity while it transits to these organelles.

Comparative transcriptome analyses on terpenoids metabolism in field- and mountain-cultivated ginseng roots

BACKGROUND

There exist differences in morphological traits and phytochemical compositions between field- and mountain-cultivated Panax ginseng (FCG and MCG), which might be attributed to variations of terpenoids metabolism adapting to different growth conditions. The present work aims to uncover these variations.

RESULTS

Among 26,648 differentially expressed genes, 496 genes distributed in seven dominant terpenoids pathways were identified. Diterpenoids and triterpenoids biosynthesis genes were significantly higher-expressed in FCG root. Conversely, biosynthesis of carotenoids was significantly more active in MCG root. Additionally, terpenoids backbones, monoterpenoids, sesquiterpenoids, and terpenoid-quinones biosyntheses were neither obviously inclined. Our determination also revealed that there were more gibberellins and steroids accumulated in FCG root which might be responsible for its quick vegetative growth, and enriched abscisic acid and germacrenes as well as protopanaxatriol-type ginsenosides might be major causes of enhanced stress-resistance in MCG root.

CONCLUSIONS

The study firstly provided an overview of terpenoids metabolism in roots of FCG and MCG in elucidating the underlying mechanisms for their different morphological appearances and phytochemical compositions.