The biochemical activities of dirigent proteins (DPs) give rise to distinct complex classes of plant phenolics. DPs apparently began to emerge during the aquatic-to-land transition, with phylogenetic ...analyses revealing the presence of numerous DP subfamilies in the plant kingdom. The vast majority (>95%) of DPs in these large multigene families still await discovery of their biochemical functions. Here, we elucidated the 3D structures of two pterocarpan-forming proteins with dirigent-like domains. Both proteins stereospecifically convert distinct diastereomeric chiral isoflavonoid precursors to the chiral pterocarpans, (–)- and (+)-medicarpin, respectively. Their 3D structures enabled comparisons with stereoselective lignan– and aromatic terpenoid–forming DP orthologs. Each protein provides entry into diverse plant natural products classes, and our experiments suggest a common biochemical mechanism in binding and stabilizing distinct plant phenol–derived mono- and bis-quinone methide intermediates during different C–C and C–O bond–forming processes. These observations provide key insights into both their appearance and functional diversification of DPs during land plant evolution/adaptation. The proposed biochemical mechanisms based on our findings provide important clues to how additional physiological roles for DPs and proteins harboring dirigent-like domains can now be rationally and systematically identified.
Early randomized clinical trials (RCTs)1–4 evaluating the efficacy of intravenous iron replacement in heart failure patients with iron deficiency showed promising results in improving objective ...clinical outcomes, including heart failure hospitalizations and cardiovascular mortality. The 2017 ACC/AHA/HFSA focused guideline update provides a IIb recommendation for intravenous iron repletion in NYHA class II and III heart failure patients and iron deficiency to improve functional status and quality of life.5 Most recently, the results of the AFFIRM-AHF (A Randomized, Double-blind Placebo-Controlled Trial Comparing the Effect of Intravenous Ferric Carboxymaltose on Hospitalisations and Mortality in Iron Deficient Subjects Admitted for Acute Heart Failure) was presented in the American Heart Association Scientific Sessions and has refueled the interest regarding the utility of intravenous iron therapy in patients with heart failure.4 We aimed to pool results from all randomized controlled trials evaluating the efficacy of intravenous iron in improving cardiovascular outcomes in patients with heart failure with reduced ejection fraction (HFrEF). Randomized trials examining the role of oral iron on improving clinical endpoints in heart failure patients have failed to show benefit likely due to poor absorption of oral iron in the setting of chronic inflammatory state associated with heart failure.1–4 In conclusion, in patients with HFrEF and iron deficiency, treatment with intravenous iron therapy has reduced the risk of heart failure hospitalization by almost 30% with no difference in all-cause mortality and cardiovascular mortality compared to standard of care.Disclosures The authors have no conflicts of interest to report.
How stereoselective monolignol-derived phenoxy radical-radical coupling reactions are differentially biochemically orchestrated in planta, whereby for example they afford (+)- and (−)-pinoresinols, ...respectively, is both a fascinating mechanistic and evolutionary question. In earlier work, biochemical control of (+)-pinoresinol formation had been established to be engendered by a (+)-pinoresinol-forming dirigent protein in Forsythia intermedia, whereas the presence of a (−)-pinoresinol-forming dirigent protein was indirectly deduced based on the enantiospecificity of downstream pinoresinol reductases (AtPrRs) in Arabidopsis thaliana root tissue. In this study of 16 putative dirigent protein homologs in Arabidopsis, AtDIR6, AtDIR10, and AtDIR13 were established to be root-specific using a β-glucuronidase reporter gene strategy. Of these three, in vitro analyses established that only recombinant AtDIR6 was a (−)-pinoresinol-forming dirigent protein, whose physiological role was further confirmed using overexpression and RNAi strategies in vivo. Interestingly, its closest homolog, AtDIR5, was also established to be a (−)-pinoresinol-forming dirigent protein based on in vitro biochemical analyses. Both of these were compared in terms of properties with a (+)-pinoresinol-forming dirigent protein from Schizandra chinensis. In this context, sequence analyses, site-directed mutagenesis, and region swapping resulted in identification of putative substrate binding sites/regions and candidate residues controlling distinct stereoselectivities of coupling modes.
Background: How vascular plants control phenoxy radical coupling is enigmatic.
Results: Two dirigents engendered (−)-pinoresinol formation in Arabidopsis. Coupling stereoselectivity was reversed from (+)- to (−)-pinoresinol through swapping identical regions.
Conclusion: Novel insights into stereoselective control over phenoxy radical coupling were obtained.
Significance: This is the first report of dirigent-mediated phenoxy radical coupling control leading to opposite stereoselectivities and identification of protein regions involved.
Dirigent protein homolog DRR206 is involved in phytoalexin (lignan) biosynthesis, and the encoding gene is induced upon fungal exposure. MALDI mass spectrometry imaging established that both the ...monoglucoside derived from (+)-pinoresinol, and the isoflavonoid pisatin, were co-localized in infected endocarp epidermal cells where pathway genes were also detected. Display omitted
•The gene encoding DRR206, a dirigent protein homolog, was induced upon fungal exposure of pea pod.•Recombinant DRR206 engendered stereoselective formation of (+)-pinoresinol.•Pinoresinol monoglucoside was detected as a phytoalexin response. MALDI MS imaging established that pinoresinol monoglucoside and pisatin were co-localized. Co-localization was in endocarp epidermal cells.
Continually exposed to potential pathogens, vascular plants have evolved intricate defense mechanisms to recognize encroaching threats and defend themselves. They do so by inducing a set of defense responses that can help defeat and/or limit effects of invading pathogens, of which the non-host disease resistance response is the most common. In this regard, pea (Pisum sativum) pod tissue, when exposed to Fusarium solani f. sp. phaseoli spores, undergoes an inducible transcriptional activation of pathogenesis-related genes, and also produces (+)-pisatin, its major phytoalexin. One of the inducible pathogenesis-related genes is Disease Resistance Response-206 (DRR206), whose role in vivo was unknown. DRR206 is, however, related to the dirigent protein (DP) family. In this study, its biochemical function was investigated in planta, with the metabolite associated with its gene induction being pinoresinol monoglucoside. Interestingly, both pinoresinol monoglucoside and (+)-pisatin were co-localized in pea pod endocarp epidermal cells, as demonstrated using matrix-assisted laser desorption/ionization (MALDI) mass spectrometry imaging. In addition, endocarp epidermal cells are also the site for both chalcone synthase and DRR206 gene expression. Taken together, these data indicate that both (+)-pisatin and pinoresinol monoglucoside function in the overall phytoalexin responses.
Background There is a lack of contemporary data on cardiogenic shock (CS) in‐hospital mortality trends. Methods and Results Patients with CS admitted January 1, 2004 to December 31, 2018, were ...identified from the US National Inpatient Sample. We reported the crude and adjusted trends of in‐hospital mortality among the overall population and selected subgroups. Among a total of 563 949 644 hospitalizations during the period from January 1, 2004, to December 30, 2018, 1 254 358 (0.2%) were attributed to CS. There has been a steady increase in hospitalizations attributed to CS from 122 per 100 000 hospitalizations in 2004 to 408 per 100 000 hospitalizations in 2018 ( P trend <0.001). This was associated with a steady decline in the adjusted trends of in‐hospital mortality during the study period in the overall population (from 49% in 2004 to 37% in 2018; P trend <0.001), among patients with acute myocardial infarction CS (from 43% in 2004 to 34% in 2018; P trend <0.001), and among patients with non–acute myocardial infarction CS (from 52% in 2004 to 37% in 2018; P trend <0.001). Consistent trends of reduced mortality were seen among women, men, different racial/ethnic groups, different US regions, and different hospital sizes, regardless of the hospital teaching status. Conclusions Hospitalizations attributed to CS have tripled in the period from January 2004 to December 2018. However, there has been a slow decline in CS in‐hospital mortality during the studied period. Further studies are necessary to determine if the recent adoption of treatment algorithms in treating patients with CS will further impact in‐hospital mortality.
Two western red cedar pinoresinol‐lariciresinol reductase (PLR) homologues were studied to determine their enantioselective, substrate versatility, and kinetic properties. PLRs are downstream of ...dirigent protein engendered, coniferyl alcohol derived, stereoselective coupling to afford entry into the 8‐ and 8′‐linked furofuran lignan, pinoresinol. Our investigations showed that each PLR homolog can enantiospecifically metabolize different furofuran lignans with modified aromatic ring substituents, but where phenolic groups at both C4/C4′ are essential for catalysis. These results are consistent with quinone methide intermediate formation in the PLR active site. Site‐directed mutagenesis and kinetic measurements provided additional insight into factors affecting enantioselectivity and kinetic properties. From these data, PLRs can be envisaged to allow for the biotechnological potential of generation of various lignan skeleta, that could be differentially “decorated” on their aromatic ring substituents, via the action of upstream dirigent proteins.
A graphene-based Terahertz (THz) diversity antenna using a series-fed microstrip antenna array is reported in this paper for body-worn applications under biomedical conditions. The proposed ...series-fed antenna array is constructed using a quad-band radiator. Each array comprises two quad-band elements, and two such arrays are developed to create the THz antenna array with diversity reception. The proposed diversity antenna has an overall footprint of 40 × 28 μm. The proposed array operates at 1.57 THz, 2.08 THz, 3.32 THz and 4.43 THz with 10 dB reflection coefficient bandwidth of 29 GHz, 49 GHz, 55 GHz and 99 GHz, respectively. The antenna elements are spaced at a distance of 26 μm to achieve mutual coupling less than − 25 dB. The realized antenna gain is 4.5 dBi, 4.8 dBi, 5 dBi, 5.2 dBi at 1.57 THz, 2.08 THz, 3.32 THz and 4.43 THz, respectively. The diversity metrics such as envelope correlation coefficient, adaptive diversity gain, effective diversity gain, mean effective gain and the cumulative distribution function are evaluated and presented. The results indicate that the proposed two-element antenna array is a suitable candidate for diversity reception in wireless body area networks operating in the THz regime.
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