The Impact of Diaphorina citri-Vectored 'Candidatus Liberibacter asiaticus' on Citrus Metabolism.

'Candidatus Liberibacter asiaticus' is associated with the devastating citrus disease Huanglongbing (HLB). It is transmitted by grafting infected material to healthy plants and by the feeding of the Asian citrus psyllid (Diaphorina citri). Previously, we demonstrated that a metabolomics approach using proton-nuclear magnetic resonance spectroscopy discriminates healthy from diseased plants via grafting. This work assessed the capability of this technology in discriminating healthy and diseased plants when the bacterium is vectored by psyllids. One-year-old greenhouse-grown 'Lisbon' lemon trees were exposed to either carrier psyllids (exposed, n = 10), or psyllids that were free of 'Candidatus Liberibacter asiaticus' (control, n = 6). Leaf metabolites were tracked for 1 year and disease diagnosis was made using quantitative PCR. Overall, 31 water-soluble metabolites were quantified in leaves, including four sugars and 12 amino acids. Analysis via nonmetric multidimensional scaling and principal component analysis revealed significant differences between the leaf metabolome of control versus infected trees beginning at 8 weeks postexposure, including alterations in glucose and quinic acid concentrations. These findings provide a longitudinal overview of the metabolic effects of HLB during the early phases of disease, and confirm previous experimental work demonstrating that infection elicits changes in the leaf metabolome that enables discrimination between healthy and infected plants. Here we demonstrate that the mode of inoculation (i.e., graft versus psyllid) results in a similar pathology.

Impact of grapevine red blotch disease on primary and secondary metabolites in 'Cabernet Sauvignon' grape tissues.

The grapevine red blotch disease (GRBD) was first noticed in 2008, impacting grape ripening. In general, GRBD reduces grape and wine quality resulting in significant economic losses. The purpose of the present study was to evaluate the effect of GRBD on agronomical parameters of 'Cabernet Sauvignon' vines at harvest. Using a metabolomics approach, the influence on primary and secondary metabolite profiling in skin + pulp/flesh and seeds were also determined. GRBD influenced °Brix and berry weight, as well as primary and secondary metabolites in both tissues. 1D 1H NMR was effective in quantifying the main primary and secondary metabolites affected by GRBD. RP-HPLC was similarly able to quantify the main phenolics affected. Multivariate analysis showed the influence of the virus on grape metabolites using both tools in two berry tissues. The effectiveness of both tools to describe sample variability was compared and the most affected metabolites in each tissue could be identified.

Trunk Girdling Increased Stomatal Conductance in Cabernet Sauvignon Grapevines, Reduced Glutamine, and Increased Malvidin-3-Glucoside and Quercetin-3-Glucoside Concentrations in Skins and Pulp at Harvest.

Girdling is a traditional horticultural practice applied at fruit set or other phenological stages, and is used mostly as a vine management. In grapevines, it is used primarily for table grapes to improve berry weight, sugar content, color, and to promote early harvest. The objective of this study was to evaluate the effect of trunk girdling applied at veraison, in 'Cabernet Sauvignon' wine grapes (Vitis vinifera L.), on agronomical and physiological parameters during vine development from the onset of ripening (veraison) to harvest, and additionally to quantify the effect of girdling on primary and secondary metabolism. Girdling was applied 146 days after pruning (dap) at veraison, when berry sampling for metabolomics and agronomical evaluations commenced, with a further three sampling dates until harvest, at 156 dap (30% maturation, 10 days after girdling-dag), 181 dap (70% maturation, 35 dag), and 223 dap (commercial harvest, 77 dag). Skin/pulp and seed tissues were extracted separately and metabolomics was performed using one-dimensional proton nuclear magnetic resonance (1D 1H NMR) spectroscopy and high performance liquid chromatography (HPLC-DAD). At harvest, girdling significantly increased stomatal conductance (gs) in vines, decreased glutamine concentrations, and increased anthocyanin and flavonol concentrations in the skin/pulp tissues of grape berries. Berry weight was reduced by 27% from 181 dap to harvest, and was significantly higher in grapes from girdled vines at 181 dap. Sugars, organic acids, and other amino acids in skin/pulp or seeds were not significantly different, possibly due to extra-fascicular phloem vessels transporting metabolites from leaves to the roots. Using a metabolomics approach, differences between skin/pulp and seeds tissues were meaningful, and a greater number of secondary metabolites in skin/pulp was affected by girdling than in seeds. Girdling is a simple technique that could easily be applied commercially on vine management to improve berry color and other phenolics in 'Cabernet Sauvignon' grapes.

Metabolome and Microbiome Signatures in the Roots of Citrus Affected by Huanglongbing.

Huanglongbing (HLB) is a severe, incurable citrus disease caused by the bacterium 'Candidatus Liberibacter asiaticus' (CLas). Although citrus leaves serve as the site of initial infection, CLas is known to migrate to and colonize the root system; however, little is known about the impact of CLas infection on root metabolism and resident microbial communities. Scions of 'Lisbon' lemon and 'Washington Navel' orange grafted onto 'Carrizo' rootstock were grafted with either CLas-infected citrus budwood or uninfected budwood. Roots were obtained from trees 46 weeks after grafting and analyzed via 1H nuclear magnetic resonance spectroscopy to identify water-soluble root metabolites and high-throughput sequencing of 16S rRNA and ITS gene amplicons to determine the relative abundance of bacterial and fungal taxa in the root rhizosphere and endosphere. In both citrus varieties, 27 metabolites were identified, of which several were significantly different between CLas(+) and control plants. CLas infection also appeared to alter the microbial community structure near and inside the roots of citrus plants. Nonmetric multidimensional scaling (NMDS) and a principal coordinate analysis (PCoA) revealed distinct metabolite and microbial profiles, demonstrating that CLas impacts the root metabolome and microbiome in a manner that is variety-specific.

Beyond the Cholesterol-Lowering Effect of Soy Protein: A Review of the Effects of Dietary Soy and Its Constituents on Risk Factors for Cardiovascular Disease.

The hypocholesterolemic effect of soy is well-documented and this has led to the regulatory approval of a health claim relating soy protein to a reduced risk of cardiovascular disease (CVD). However, soybeans contain additional components, such as isoflavones, lecithins, saponins and fiber that may improve cardiovascular health through independent mechanisms. This review summarizes the evidence on the cardiovascular benefits of non-protein soy components in relation to known CVD risk factors such as hypertension, hyperglycemia, inflammation, and obesity beyond cholesterol lowering. Overall, the available evidence suggests non-protein soy constituents improve markers of cardiovascular health; however, additional carefully designed studies are required to independently elucidate these effects. Further, work is also needed to clarify the role of isoflavone-metabolizing phenotype and gut microbiota composition on biological effect.