Induction of tocopherol biosynthesis through heat shock treatment in Arabidopsis

ABSTRACT Plants have developed various self-defense systems to survive many types of unfavorable conditions. Heat shock (HS) treatment, an abiotic stress, activates salicylic acid (SA) biosynthesis to enhance resistance to biotic stresses in some plant species. Since SA is produced from the shikimate pathway, other related metabolic pathways were expected to be upregulated by HS treatment. We speculated that tocopherol biosynthesis utilizing chorismic acid would be activated by HS treatment. In Arabidopsis, expression analysis of tocopherol biosynthetic genes, HPPD, VTE2, VTE3, VTE1, and VTE4, in combination with measurement of metabolites, indicated that HS treatment enhanced the biosynthesis and accumulation of tocopherols. Analyses using an SA biosynthesis-deficient mutant indicated that the upregulation of tocopherol biosynthesis was independent of the SA-mediated signaling pathway.

Independent Tryptophan pathway in Trichoderma asperellum and T koningiopsis: New insights with bioinformatic and molecular analysis

ABSTRACTThe synthesis of Indole Acetic Acid from tryptophan has been described in plants, fungi and bacteria; it is thus known as tryptophan-dependent indole acetic acid. Four possible pathways of IAA formation have been described, including the indole acetonitrile acid (IAN), indole acetamide (IAM), indole-pyruvic (IAP) and tryptamine (TRM) pathways. Of these, the indole acetonitrile pathway is particularly important because when this compound is transformed into IAA, a nitrogenated molecule is released. The microorganisms that have this pathway are thus called nitrogen fixers. There is another little-studied pathway called TRP-Independent, so-called because the IAA that is formed in it can have an exogenous origin, chorismic acid (CHA), and it enters the pathway through anthranilic acid (ANA). The TRP-Independent pathway is made up of three stages. The first from CHA to ANA, the second from AA to IAA and the third from TRP to ANA through Kynurenine (KYN). This work describes the different stages of the pathway, as well as the enzymes and the genes that control the production of IAA, using a bioinformatic analysis of the genes involved, which were identified by PCR. An expression analysis showed that only T asperellum has the necessary genes to incorporate ANA into the TRP-I pathway and synthesize IAA through it. The analysis also detected the gene that regulates anthranilate phosphoribosyl transferase (AFT), an enzyme necessary for the synthesis of AIA from ANA; the presence of this gene was confirmed in the two species analyzed.

Antimicrobial Secondary Metabolites from the Seawater-Derived Fungus Aspergillus sydowii SW9

Marine-derived fungi are considered to be valuable producers of bioactive secondary metabolites used as lead compounds with medicinal importance. In this study, chemical investigation of the seawater-derived fungus Aspergillus sydowii SW9 led to the isolation and identification of one new quinazolinone alkaloid, 2-(4-hydroxybenzyl)-4-(3-acetyl)quinazolin-one (1), one new aromatic bisabolene-type sesquiterpenoid, (2) and one new chorismic acid analogue (3), as well as two known alkaloids (compounds 4 and 5). Their structures were determined by extensive 1D/2D NMR and mass spectrometric data, and the absolute configurations of 2 and 3 were assigned by the analysis of ECD spectra aided by quantum chemical computations. Compounds 1, 2, and 4 exhibited selective inhibitory activities against the human pathogenic bacteria Escherichia coli, Staphylococcus aureus, S. epidermidis, and Streptococcus pneumoniae, with MIC values ranging from 2.0 to 16 μg/mL.

PBS3 is the missing link in plant-specific isochorismate-derived salicylic acid biosynthesis

The phytohormone salicylic acid (SA) is a central regulator of plant immunity. Despite such functional importance, our knowledge of its biosynthesis is incomplete. Previous work showed that SA is synthesized from chorismic acid in plastids. The bulk of pathogen-induced SA derives from isochorismate generated by the catalytic activity of ISOCHORISMATE SYNTHASE1 (ICS1). How and in which cellular compartment isochorismate is converted to SA is unknown. Here we show that the pathway downstream of isochorismate requires only two additional proteins: the plastidial isochorismate exporter ENHANCED DISEASE SUSCEPTIBILITY5 (EDS5) and the cytosolic amido-transferase AvrPphB SUSCEPTIBLE3 (PBS3). PBS3 catalyzes the conjugation of glutamate to isochorismate. The reaction product isochorismate-9-glutamate spontaneously decomposes into enolpyruvyl-N-glutamate and SA. This previously unknown reaction mechanism appears to be conserved throughout the plant kingdom.One Sentence SummarySalicylic acid is synthesized via isochorismate-9-glutamate by PBS3.

Diacidene, a Polyene Dicarboxylic Acid from a Micromonospora Isolate from the German Wadden Sea

Micromonospora sp. strain DB620 was isolated from a Wadden Sea sediment sample collected near Büsum (Germany) and is closely related (99% 16S-rRNA gene sequence similarity) to Micromonospora coxensis strain MTCC8093. It produced a new polyene dicarboxylic acid named diacidene (1) and in addition a derivative of chorismic acid, the known 3-[(1-carboxyvinyl)oxy]benzoic acid. The structure elucidation of 1 was achieved by applying different 1D and 2D NMR techniques as well as mass spectrometry and UV spectroscopy

Requirement of Siderophore Biosynthesis for Plant Colonization by Salmonella enterica

ABSTRACTContaminated fresh produce has become the number one vector of nontyphoidal salmonellosis to humans. However,Salmonella entericagenes essential for the life cycle of the organism outside the mammalian host are for the most part unknown. Screening deletion mutants led to the discovery that anaroAmutant had a significant root colonization defect due to a failure to replicate. AroA is part of the chorismic acid biosynthesis pathway, a central metabolic node involved in aromatic amino acid and siderophore production. Addition of tryptophan or phenylalanine to alfalfa root exudates did not restorearoAmutant replication. However, addition of ferrous sulfate restored replication of thearoAmutant, as well as alfalfa colonization. Tryptophan and phenylalanine auxotrophs had minor plant colonization defects, suggesting that suboptimal concentrations of these amino acids in root exudates were not major limiting factors forSalmonellareplication. AnentBmutant defective in siderophore biosynthesis had colonization and growth defects similar to those of thearoAmutant, and the defective phenotype was complemented by the addition of ferrous sulfate. Biosynthetic genes of eachSalmonellasiderophore, enterobactin and salmochelin, were upregulated in alfalfa root exudates, yet only enterobactin was sufficient for plant survival and persistence. Similar results in lettuce leaves indicate that siderophore biosynthesis is a widespread or perhaps universal plant colonization fitness factor forSalmonella, unlike phytobacterial pathogens, such asPseudomonasandXanthomonas.