Independent Evolution of Six Families of Halogenating Enzymes.

Halogenated natural products are widespread in the environment, and the halogen atoms are typically vital to their bioactivities. Thus far, six families of halogenating enzymes have been identified: cofactor-free haloperoxidases (HPO), vanadium-dependent haloperoxidases (V-HPO), heme iron-dependent haloperoxidases (HI-HPO), non-heme iron-dependent halogenases (NI-HG), flavin-dependent halogenases (F-HG), and S-adenosyl-L-methionine (SAM)-dependent halogenases (S-HG). However, these halogenating enzymes with similar biological functions but distinct structures might have evolved independently. Phylogenetic and structural analyses suggest that the HPO, V-HPO, HI-HPO, NI-HG, F-HG, and S-HG enzyme families may have evolutionary relationships to the α/β hydrolases, acid phosphatases, peroxidases, chemotaxis phosphatases, oxidoreductases, and SAM hydroxide adenosyltransferases, respectively. These halogenating enzymes have established sequence homology, structural conservation, and mechanistic features within each family. Understanding the distinct evolutionary history of these halogenating enzymes will provide further insights into the study of their catalytic mechanisms and halogenation specificity

Evolutionary relationships between the HI-HPO and the peroxidases.

<p>The phylogenetic tree was reconstructed using the Neighbor-Joining method. The representative HI-HPO enzymes are marked (◆).</p

Evolutionary relationships between the NI-HG and the chemotaxis phosphatases.

<p>The phylogenetic tree was reconstructed using the Neighbor-Joining method. The representative NI-HG enzymes are marked (■).</p

Evolutionary relationships between the cofactor-free HPO and the α/β hydrolases.

<p>The phylogenetic tree was reconstructed using the Neighbor-Joining method. The representative HPO enzymes are marked (▲).</p

Evolutionary relationships between the F-HG and the oxidoreductases.

<p>The phylogenetic tree was reconstructed using the Neighbor-Joining method. The representative F-HG enzymes are marked (●).</p

Genomic analysis, trajectory tracking, and field surveys reveal sources and long-distance dispersal routes of wheat stripe rust pathogen in China

Identifying sources of phytopathogen inoculum and determining their contributions to disease outbreaks are essential for predicting disease development and establishing control strategies. Puccinia striiformis f. sp. tritici (Pst), the causal agent of wheat stripe rust, is an airborne fungal pathogen with rapid virulence variation that threatens wheat production through its long-distance migration. Because of wide variation in geographic features, climatic conditions, and wheat production systems, Pst sources and related dispersal routes in China are largely unclear. In the present study, we performed genomic analyses of 154 Pst isolates from all major wheat-growing regions in China to determine Pst population structure and diversity. Through trajectory tracking, historical migration studies, genetic introgression analyses, and field surveys, we investigated Pst sources and their contributions to wheat stripe rust epidemics. We identified Longnan, the Himalayan region, and the Guizhou Plateau, which contain the highest population genetic diversities, as the Pst sources in China. Pst from Longnan disseminates mainly to eastern Liupan Mountain, the Sichuan Basin, and eastern Qinghai; that from the Himalayan region spreads mainly to the Sichuan Basin and eastern Qinghai; and that from the Guizhou Plateau migrates mainly to the Sichuan Basin and the Cen-tral Plain. These findings improve our current understanding of wheat stripe rust epidemics in China and emphasize the need for managing stripe rust on a national scale

Targeted Metabolomics Reveals a Protective Role for Basal PPARα in Cholestasis Induced by α‑Naphthylisothiocyanate

α-Naphthylisothiocyanate (ANIT) is an experimental agent used to induce intrahepatic cholestasis. The <i>Ppara</i>-null mouse line is widely employed to explore the physiological and pathological roles of PPARα. However, little is known about how PPARα influences the hepatotoxicity of ANIT. In the present study, wild-type and <i>Ppara</i>-null mice were orally treated with ANIT to induce cholestasis. The serum metabolome of wild-type mice segregated from that of the <i>Ppara</i>-null mice, driven by changes of bile acid (BA) metabolites. Alkaline phosphatase and total BAs were elevated preferentially in <i>Ppara</i>-null mice, which correlated with changes in <i>Cyp7a1</i>, <i>Cyp8b1</i>, <i>Mrp3</i>, <i>Cyp3a11</i>, <i>Cyp2b10</i>, <i>Ugt1a2</i>, and <i>Ugt1a5</i> genes and showed cross-talk between basal PPARα and potentially adaptive pathways. <i>Il6</i>, <i>Tnfa</i>, and target genes in the STAT3 pathway (<i>Socs3</i>, <i>Fga</i>, <i>Fgb</i>, and <i>Fgg</i>) were up-regulated in <i>Ppara</i>-null mice but not in wild-type mice. The JNK pathway was activated in both mouse lines, while NF-κB and STAT3 were activated only in <i>Ppara</i>-null mice. These data suggest protection against cholestasis by basal PPARα involves regulation of BA metabolism and inhibition of NF-κB/STAT3 signaling. Considering studies on the protective effects of both basal and activated PPARα, caution should be exercised when one attempts to draw conclusions in which the PPARα is modified by genetic manipulation, fasting, or activation in pharmacological and toxicological studies

“Pseudo” γ-Butyrolactone Receptors Respond to Antibiotic Signals to Coordinate Antibiotic Biosynthesis*

In actinomycetes, the onset of secondary metabolite biosynthesis is often triggered by the quorum-sensing signal γ-butyrolactones (GBLs) via specific binding to their cognate receptors. However, the presence of multiple putative GBL receptor homologues in the genome suggests the existence of an alternative regulatory mechanism. Here, in the model streptomycete Streptomyces coelicolor, ScbR2 (SCO6286, a homologue of GBL receptor) is shown not to bind the endogenous GBL molecule SCB1, hence designated “pseudo” GBL receptor. Intriguingly, it could bind the endogenous antibiotics actinorhodin and undecylprodigiosin as ligands, leading to the derepression of KasO, an activator of a cryptic type I polyketide synthase gene cluster. Likewise, JadR2 is also a putative GBL receptor homologue in Streptomyces venezuelae, the producer of chloramphenicol and cryptic antibiotic jadomycin. It is shown to coordinate their biosynthesis via direct repression of JadR1, which activates jadomycin biosynthesis while repressing chloramphenicol biosynthesis directly. Like ScbR2, JadR2 could also bind these two disparate antibiotics, and the interactions lead to the derepression of jadR1. The antibiotic responding activities of these pseudo GBL receptors were further demonstrated in vivo using the lux reporter system. Overall, these results suggest that pseudo GBL receptors play a novel role to coordinate antibiotic biosynthesis by binding and responding to antibiotics signals. Such an antibiotic-mediated regulatory mechanism could be a general strategy to coordinate antibiotic biosynthesis in the producing bacteria