Analysis of Two New Arabinosyltransferases Belonging to the Carbohydrate-Active Enzyme (CAZY) Glycosyl Transferase Family1 Provides Insights into Disease Resistance and Sugar Donor Specificity

Glycosylation of small molecules is critical for numerous biological processes in plants, including hormone homeostasis, neutralization of xenobiotics, and synthesis and storage of specialized metabolites. Glycosylation of plant natural products is usually carried out by uridine diphosphate-dependent glycosyltransferases (UGTs). Triterpene glycosides (saponins) are a large family of plant natural products that determine important agronomic traits such as disease resistance and flavor and have numerous pharmaceutical applications. Most characterised plant natural product UGTs are glucosyltransferases, and little is known about enzymes that add other sugars. Here we report the discovery and characterization of AsAAT1 (UGT99D1), which is required for biosynthesis of the antifungal saponin avenacin A-1 in oat. This enzyme adds L-arabinose to the triterpene scaffold at the C-3 position, a modification critical for disease resistance. The only previously reported plant natural product arabinosyltransferase is a flavonoid arabinosyltransferase from Arabidopsis. We show that AsAAT1 has high specificity for UDP-β-L-arabinopyranose, identify two amino acids required for sugar donor specificity, and through targeted mutagenesis convert AsAAT1 into a glucosyltransferase. We further identify a second arabinosyltransferase potentially implicated in the biosynthesis of saponins that determine bitterness in soybean. Our investigations suggest independent evolution of UDP-arabinose sugar donor specificity in arabinosyltransferases in monocots and eudicots

Type F congenital quadricuspid aortic valve: A very rare case diagnosed by 3-dimenional transoesophageal echocardiography

Congenital quadricuspid aortic valve (QAV) is a rare cardiac anomaly. Several different anatomical variations of a quadricuspid aortic valve have been described. Aortic regurgitation is the predominant valvular dysfunction associated with QAV and patients tend to present in their 5(th) or 6(th) decade of life. This anomaly is rarely picked up by transthoracic echocardiogram (TTE). A comprehensive transoesophageal echocardiography (TOE) study is more likely to diagnose it. We describe a very rare type of QAV - Type F in a 52-year-old lady who presented with symptoms of shortness of breath and pre-syncope. We include TOE images and intra-operative valve images

Influence of muscle mass in the assessment of lower limb strength in COPD: validation of the prediction equation

Absence of established reference values limits application of quadriceps maximal voluntary contraction (QMVC) measurement. The impact of muscle mass inclusion in predictions is unclear. Prediction equations encompassing gender, age and size with (FFM+) and without (FFM−), derived in healthy adults (n=175), are presented and compared in two COPD cohorts recruited from primary care (COPD-PC, n=112) and a complex care COPD clinic (COPD-CC, n=189). Explained variance was comparable between the prediction models (R2: FFM+: 0.59, FFM−: 0.60) as were per cent predictions in COPD-PC (88.8%, 88.3%). However, fat-free mass inclusion reduced the prevalence of weakness in COPD, particularly in COPD-CC where 11.9% fewer were deemed weak

The influence of muscle mass in the assessment of lower limb strength in COPD [Abstract]

The influence of muscle mass in the assessment of lower limb strength in COPD [Abstract

A noncanonical vacuolar sugar transferase required for biosynthesis of antimicrobial defense compounds in oat

Plants produce an array of natural products with important ecological functions. These compounds are often decorated with oligosaccharide groups that influence bioactivity, but the biosynthesis of such sugar chains is not well understood. Triterpene glycosides (saponins) are a large family of plant natural products that determine important agronomic traits, as exemplified by avenacins, antimicrobial defense compounds produced by oats. Avenacins have a branched trisaccharide moiety consisting of L-arabinose linked to 2 D-glucose molecules that is critical for antifungal activity. Plant natural product glycosylation is usually performed by uridine diphosphate-dependent glycosyltransferases (UGTs). We previously characterized the arabinosyltransferase that initiates the avenacin sugar chain; however, the enzymes that add the 2 remaining D-glucose molecules have remained elusive. Here we characterize the enzymes that catalyze these last 2 glucosylation steps. AsUGT91G16 is a classical cytosolic UGT that adds a 1,2-linked D-glucose molecule to L-arabinose. Unexpectedly, the enzyme that adds the final 1,4-linked D-glucose (AsTG1) is not a UGT, but rather a sugar transferase belonging to Glycosyl Hydrolase family 1 (GH1). Unlike classical UGTs, AsTG1 is vacuolar. Analysis of oat mutants reveals that AsTG1 corresponds to Sad3, a previously uncharacterized locus shown by mutation to be required for avenacin biosynthesis. AsTG1 and AsUGT91G16 form part of the avenacin biosynthetic gene cluster. Our demonstration that a vacuolar transglucosidase family member plays a critical role in triterpene biosynthesis highlights the importance of considering other classes of carbohydrate-active enzymes in addition to UGTs as candidates when elucidating pathways for the biosynthesis of glycosylated natural products in plants

Subtelomeric assembly of a multi-gene pathway for antimicrobial defense compounds in cereals

Non-random gene organization in eukaryotes plays a significant role in genome evolution. Here, we investigate the origin of a biosynthetic gene cluster for production of defence compounds in oat—the avenacin cluster. We elucidate the structure and organisation of this 12-gene cluster, characterise the last two missing pathway steps, and reconstitute the entire pathway in tobacco by transient expression. We show that the cluster has formed de novo since the divergence of oats in a subtelomeric region of the genome that lacks homology with other grasses, and that gene order is approximately colinear with the biosynthetic pathway. We speculate that the positioning of the late pathway genes furthest away from the telomere may mitigate against a ‘self-poisoning’ scenario in which toxic intermediates accumulate as a result of telomeric gene deletions. Our investigations reveal a striking example of adaptive evolution underpinned by remarkable genome plasticity

Retreatment for hepatitis C virus direct-acting antiviral therapy virological failure in primary and tertiary settings: The REACH-C cohort

Virological failure occurs in a small proportion of people treated for hepatitis C virus (HCV) with direct-acting antiviral (DAA) therapies. This study assessed retreatment for virological failure in a large real-world cohort. REACH-C is an Australian observational study (n = 10,843) evaluating treatment outcomes of sequential DAA initiations across 33 health services between March 2016 to June 2019. Virological failure retreatment data were collected until October 2020. Of 408 people with virological failure (81% male; median age 53; 38% cirrhosis; 56% genotype 3), 213 (54%) were retreated once; 15 were retreated twice. A range of genotype specific and pangenotypic DAAs were used to retreat virological failure in primary (n = 56) and tertiary (n = 157) settings. Following sofosbuvir/velpatasvir/voxilaprevir availability in 2019, the proportion retreated in primary care increased from 21% to 40% and median time to retreatment initiation declined from 294 to 152 days. Per protocol (PP) sustained virological response (SVR12) was similar for people retreated in primary and tertiary settings (80% vs 81%; p = 1.000). In regression analysis, sofosbuvir/velpatasvir/voxilaprevir (vs. other regimens) significantly decreased likelihood of second virological failure (PP SVR12 88% vs. 77%; adjusted odds ratio [AOR] 0.29; 95%CI 0.11–0.81); cirrhosis increased likelihood (PP SVR12 69% vs. 91%; AOR 4.26; 95%CI 1.64–11.09). Indigenous Australians had lower likelihood of retreatment initiation (AOR 0.36; 95%CI 0.15–0.81). Treatment setting and prescriber type were not associated with retreatment initiation or outcome. Virological failure can be effectively retreated in primary care. Expanded access to simplified retreatment regimens through decentralized models may increase retreatment uptake and reduce HCV-related mortality

The macroecology of chemical communication in lizards: do climatic factors drive the evolution of signalling glands?

Chemical communication plays a pivotal role in shaping sexual and ecological interactions among animals. In lizards, fundamental mechanisms of sexual selection such as female mate choice have rarely been shown to be influenced by quantitative phenotypic traits (e.g., ornaments), while chemical signals have been found to potentially influence multiple forms of sexual and social interactions, including mate choice and territoriality. Chemical signals in lizards are secreted by glands primarily located on the edge of the cloacae (precloacal glands, PG) and thighs (femoral glands), and whose interspecific and interclade number ranges from 0 to >100. However, elucidating the factors underlying the evolution of such remarkable variation remains an elusive endeavour. Competing hypotheses suggest a dominant role for phylogenetic conservatism (i.e., species within clades share similar numbers of glands) or for natural selection (i.e., their adaptive diversification results in deviating numbers of glands from ancestors). Using the prolific Liolaemus lizard radiation from South America (where precloacal glands vary from 0-14), we present one of the largest-scale tests of both hypotheses to date. Based on climatic and phylogenetic modelling, we show a clear role for both phylogenetic inertia and adaptation underlying gland variation: (i) solar radiation, net primary productivity, topographic heterogeneity and precipitation range have a significant effect on number of PG variation, (ii) humid and cold environments tend to concentrate species with a higher number of glands, (iii) there is a strong phylogenetic signal that tends to conserve the number of PG within clades. Collectively, our study confirms that the inertia of niche conservatism can be broken down by the need of species facing different selection regimes to adjust their glands to suit the demands of their specific environments

nSeP: immune and metabolic biomarkers for early detection of neonatal sepsis-protocol for a prospective multicohort study

Introduction Diagnosing neonatal sepsis is heavily dependent on clinical phenotyping as culture-positive body fluid has poor sensitivity, and existing blood biomarkers have poor specificity. A combination of machine learning, statistical and deep pathway biology analyses led to the identification of a tripartite panel of biologically connected immune and metabolic markers that showed greater than 99% accuracy for detecting bacterial infection with 100% sensitivity. The cohort study described here is designed as a large-scale clinical validation of this previous work. Methods and analysis This multicentre observational study will prospectively recruit a total of 1445 newborn infants (all gestations)—1084 with suspected early—or late-onset sepsis, and 361 controls—over 4 years. A small volume of whole blood will be collected from infants with suspected sepsis at the time of presentation. This sample will be used for integrated transcriptomic, lipidomic and targeted proteomics profiling. In addition, a subset of samples will be subjected to cellular phenotype and proteomic analyses. A second sample from the same patient will be collected at 24 hours, with an opportunistic sampling for stool culture. For control infants, only one set of blood and stool sample will be collected to coincide with clinical blood sampling. Along with detailed clinical information, blood and stool samples will be analysed and the information will be used to identify and validate the efficacy of immune-metabolic networks in the diagnosis of bacterial neonatal sepsis and to identify new host biomarkers for viral sepsis