Molecular and biochemical analysis of XDH from Phaseolus vulgaris suggest that uric acid protects the enzyme against the inhibitory effects of nitric oxide in nodules

Comparative transcriptomics revealed the ecological trap effect of linearly polarized light on Oratosquilla oratoria

Although polarized light can assist many animals in performing special visual tasks, current polarized light pollution (PLP) caused by urban construction has been shown to induce maladaptive behaviors of PL-sensitive animals and change ecological interactions. However, the underlying mechanisms remain unclear. Our previous work hypothesized that linearly polarized light (LPL) is an ecological trap for Oratosquilla oratoria, a common Stomatopoda species in the China Sea. Here we explored the underlying negative effects of artificially LPL on O. oratoria based on comparative transcriptomics. We identified 3616 differentially expressed genes (DEGs) in O. oratoria compound eyes continuous exposed to natural light (NL) and LPL scenarios. In comparison with the NL scenario, a total of 1972 up- and 1644 down- regulated genes were obtained from the O. oratoria compound eyes under LPL scenario, respectively. Furthermore, we performed functional annotation of those DEGs described above and identified 65 DEGs related to phototransduction, reproduction, immunity, and synapse. Based on the functional information, we suspected that continuous LPL exposure could block the light transmission, disrupt the reproductive process, and lead to the progressive failure of the immune response of O. oratoria. In conclusion, this study is the first to systematically describe the negative effects of artificial LPL exposure on O. oratoria at the genetic level, and it can improve the biological conservation theory behind PLP.

Flavonoid extract of saffron by-product alleviates hyperuricemia via inhibiting xanthine oxidase and modulating gut microbiota

Hyperuricemia was associated with the overproduction or inadequate excretion of uric acid, while its association with gut microbiota has emerged although few studies were focused on it. Previously, we have reported a flavonoid extract from saffron floral bio-residues lowered uric acid in potassium oxonate-induced hyperuricemic mice. In this study, the impacts of the flavonoid extract on potassium oxonate-induced hyperuricemic rats were evaluated through its effects on serum, renal, intestinal uric acid, and xanthine oxidase activity. At the same time, the microbial and metabolic features of the flavonoid extract against hyperuricemia were explored using 16S rRNA sequencing techniques and serum metabolomics, respectively. According to the results, the flavonoid extract lowered serum and intestinal uric acid levels in hyperuricemic rats without kidney damage. On the one hand, it inhibited serum and liver xanthine oxidase activities and down-regulated the expression of hepatic xanthine oxidase. On the other hand, it ameliorated the hyperuricemia-associated gut microbiota dysbiosis and alleviated the disturbance of serum metabolome, especially of lipid and amino acid metabolites. The results suggested that the flavonoid extract of saffron floral bio-residues exerts a potent antihyperuricemia effect by inhibiting xanthine oxidase to decrease uric acid production and modulating gut microbiota related to host metabolism.

Enzymes and cellular interplay required for flux of fixed nitrogen to ureides in bean nodules

Tropical legumes transport fixed nitrogen in form of ureides (allantoin and allantoate) over long distances from the nodules to the shoot. Ureides are formed in nodules from purine mononucleotides by a partially unknown reaction network that involves bacteroid-infected and uninfected cells. Here, we demonstrate by metabolic analysis of CRISPR mutant nodules of Phaseolus vulgaris defective in either xanthosine monophosphate phosphatase (XMPP), guanosine deaminase (GSDA), the nucleoside hydrolases 1 and 2 (NSH1, NSH2) or xanthine dehydrogenase (XDH) that nodule ureide biosynthesis involves these enzymes and requires xanthosine and guanosine but not inosine monophosphate catabolism. Interestingly, promoter reporter analyses revealed that XMPP, GSDA and XDH are expressed in infected cells, whereas NSH1, NSH2 and the promoters of the downstream enzymes urate oxidase (UOX) and allantoinase (ALN) are active in uninfected cells. The data suggest a complex cellular organization of ureide biosynthesis with three transitions between infected and uninfected cells.

Tropical legumes export fixed nitrogen from nodules as ureides. Here, the authors describe how ureides are produced by several biosynthetic enzymes in different nodule cell types and provide explanations for metabolic compartmentation.