Toxoplasma gondii is a common protozoan parasite that infects a wide range of hosts, including livestock and humans. Previous studies have suggested that the type 2 fatty acid synthesis (FAS2) pathway, located in the apicoplast (a nonphotosynthetic plastid relict), is crucial for the parasite's survival. Here we examined the physiological relevance of fatty acid synthesis in T. gondii by focusing on the pyruvate dehydrogenase complex and malonyl-CoA-[acyl carrier protein] transacylase (FabD), which are located in the apicoplast to drive de novo fatty acid biosynthesis. Our results disclosed unexpected metabolic resilience of T. gondii tachyzoites, revealing that they can tolerate CRISPR/Cas9–assisted genetic deletions of three pyruvate dehydrogenase subunits or FabD. All mutants were fully viable in prolonged cultures, albeit with impaired growth and concurrent loss of the apicoplast. Even more surprisingly, these mutants displayed normal virulence in mice, suggesting an expendable role of the FAS2 pathway in vivo. Metabolic labeling of the Δpdh-e1α mutant showed reduced incorporation of glucose-derived carbon into fatty acids with medium chain lengths (C14:0 and C16:0), revealing that FAS2 activity was indeed compromised. Moreover, supplementation of exogenous C14:0 or C16:0 significantly reversed the growth defect in the Δpdh-e1α mutant, indicating salvage of these fatty acids. Together, these results demonstrate that the FAS2 pathway is dispensable during the lytic cycle of Toxoplasma because of its remarkable flexibility in acquiring fatty acids. Our findings question the long-held assumption that targeting this pathway has significant therapeutic potential for managing Toxoplasma infections.
Camellia japonica petals are colorful, rich in anthocyanins, and possess important ornamental, edible, and medicinal value. However, the regulatory mechanism of anthocyanin accumulation in C. japonica is still unclear. In this study, an integrative analysis of the metabolome and transcriptome was conducted in five C. japonica cultivars with different petal colors. Overall, a total of 187 flavonoids were identified (including 25 anthocyanins), and 11 anthocyanins were markedly differentially accumulated among these petals, contributing to the different petal colors in C. japonica. Moreover, cyanidin-3-O-(6″-O-malonyl) glucoside was confirmed as the main contributor to the red petal phenotype, while cyanidin-3-O-rutinoside, peonidin-3-O-glucoside, cyanidin-3-O-glucoside, and pelargonidin-3-O-glucoside were responsible for the deep coloration of the C. japonica petals. Furthermore, a total of 12,531 differentially expressed genes (DEGs) and overlapping DEGs (634 DEGs) were identified by RNA sequencing, and the correlation between the expression level of the DEGs and the anthocyanin content was explored. The candidate genes regulating anthocyanin accumulation in the C. japonica petals were identified and included 37 structural genes (especially CjANS and Cj4CL), 18 keys differentially expressed transcription factors (such as GATA, MYB, bHLH, WRKY, and NAC), and 16 other regulators (mainly including transporter proteins, zinc-finger proteins, and others). Our results provide new insights for elucidating the function of anthocyanins in C. japonica petal color expression.
Toxoplasma gondii is a ubiquitous pathogen infecting one-third of the global population. A significant fraction of toxoplasmosis cases is caused by reactivation of existing chronic infections. The encysted bradyzoites during chronic infection accumulate high levels of amylopectin that is barely present in fast-replicating tachyzoites. However, the physiological significance of amylopectin is not fully understood. Here, we identified a starch synthase (SS) that is required for amylopectin synthesis in T. gondii . Genetic ablation of SS abolished amylopectin production, reduced tachyzoite proliferation, and impaired the recrudescence of bradyzoites to tachyzoites. Disruption of the parasite Ca 2+ -dependent protein kinase 2 (CDPK2) was previously shown to cause massive amylopectin accumulation and bradyzoite death. Therefore, the Δcdpk2 mutant is thought to be a vaccine candidate. Notably, deleting SS in a Δcdpk2 mutant completely abolished starch accrual and restored cyst formation as well as virulence in mice. Together these results suggest that regulated amylopectin production is critical for the optimal growth, development and virulence of Toxoplasma . Not least, our data underscore a potential drawback of the Δcdpk2 mutant as a vaccine candidate as it may regain full virulence by mutating amylopectin synthesis genes like SS.
Numerous olive cultivars have been planted in China, mainly to reap the health benefits of olive oil. This study characterized the quality and investigated the antioxidant activity of olives harvested at three different maturation stages, defined by the skin color of the olives (black, purple, and green), from three newly introduced olive cultivars (Barnea, Manzanilla and Kadesh) grown in China. The oleic acid content of olives from all three olive cultivars decreased significantly during maturation, whereas the linoleic acid content increased. The highest content of total phenols was recorded in Manzanilla cultivar (284.94 mg kg−1), whereas the lowest was recorded in Kadesh cultivar (134.82 mg kg−1). In addition, a total of 13 individual phenolic compounds were obtained, and their concentrations were significantly influenced by the cultivar and maturity (P < 0.05). Secoiridoids were the main group of phenolic compounds, but their quantity decreased during maturation. The content of secoiridoids in the Manzanilla cultivar was significantly higher than that of the Barnea and Kadesh cultivars. In general, a significant decrease (P < 0.05) in the values of antioxidant activity and the contents of pigments, α‐tocopherol, and squalene occurred during maturation. Furthermore, principal component analysis was used to classify the nine olive oil samples according to the cultivar and ripening degree.
Longan (Dimocarpus longan) is a typical southern subtropical fruit tree species that is sensitive to cold stress. C-repeat binding factors (CBFs), as transcription factors, are crucial components involved in the molecular regulation of the plant response to cold stress. However, the role of CBF homologs in the cold response regulation of longan remains largely unknown. Here, three novel CBF genes, DlCBF1, DlCBF2, and DlCBF3, were cloned from longan. DlCBF1 and DlCBF2 contain an AP2 domain and PKKPAGR and DSAWR CBF signature motifs, while DlCBF3 has mutations within these conserved signature motifs. DlCBF1/2/3 were mainly localized in the nucleus and specifically bound to CRT/DRE cis-elements, resulting in strong transcriptional activation. DlCBF1/2 exhibited tissue expression specificity, and their expression was induced by low temperature, while DlCBF3 had no tissue specificity and barely responded to low temperature. DlCBF1, DlCBF2, and DlCBF3 overexpression in Arabidopsis-enhanced cold tolerance by increasing proline accumulation and reducing reactive oxygen species (ROS) content, accompanied by upregulated expression of cold-responsive genes (AtRD29A, AtCOR15A, AtCOR47, and AtKIN1) in the CBF cold stress response signaling pathway. In conclusion, the biological functions of DlCBF1/2/3 were somewhat conserved, but slow expression of DlCBF1/2 and low expression of DlCBF3 may partly cause the cold sensitivity of longan. Collectively, these results indicated that differences exist in the expression and function of CBF orthologs in the cold-sensitive plant species longan, and these findings may help to improve the understanding of the cold response regulation mechanism and provide important theoretical support for coldtolerant breeding of longan.
BackgroundNeuromyelitis optica spectrum disorders (NMOSDs) are severe inflammatory diseases mediated mainly by humoral and cellular immunity. Circulating follicular helper T (Tfh) cells are thought to be involved in the pathogenesis of NMOSD, and serum C-X-C motif ligand 13 (CXCL13) levels reflect the effects of Tfh cells on B-cell-mediated humoral immunity. Immune cell and cytokine changes during the dynamic relapsing and remitting processes in NMOSD require further exploration.Patients and methodsBlood samples were collected from 36 patients in acute and recovery phases of NMOSD, 20 patients with other noninflammatory neurological diseases (ONND) and 20 age- and sex-matched healthy volunteers. CD4+CXCR5+PD-1+ Tfh cells were detected by flow cytometry, and serum CXCL13 levels were assessed by enzyme-linked immunosorbent assay (ELISA).ResultsThe percentage of CD4+CXCR5+PD-1+ Tfh cells was significantly higher during the acute phase than during the recovery phase, and serum CXCL13 levels were significantly higher in patients in the acute and recovery phases of NMOSD than in the ONND and control groups. The Tfh cell percentage was positively correlated with CXCL13 levels, and both were positively correlated with Expanded Disability Status Scale (EDSS) scores and cerebrospinal fluid protein levels in patients with acute NMOSD.ConclusionCirculating Tfh cells level has the potential to be a biomarker of disease severity.
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