Shuyu Li’s scientific contributions

Natural products from medicinal plants serve as an invaluable resource for drug discovery and development. However, low-abundance natural products are often understudied due to the challenges of obtaining sufficient quantities for pharmacological testing in cells or animals. Additionally, their complex stereochemistry and functional groups make chemical synthesis and purification difficult. In this study, we showcased the power of biosynthetic approaches to explore these underexplored compounds, using the low-abundance polyphyllin trillin 6′-O-glucoside from Paris polyphylla as an example. We identified two trillin 6′-O-glucosyltransferases required for its biosynthesis and successfully reconstructed the entire pathway in Nicotiana benthamiana. We demonstrated that trillin 6′-O-glucoside exhibits anti-bacterial activity comparable to major polyphyllins like polyphyllins I, II, and VII. Notably, it also showed much lower hemolytic activity, a common side effect of those major polyphyllins. Together, our study underscores the advantages of employing biosynthetic approaches to explore natural products that exist in low or trace abundances yet possess equally important pharmacological activities.

Background Acetaminophen (APAP)-induced hepatotoxicity has attracted considerable attention in clinical settings due to the limited treatment options available. Liensinine stands out as a key alkaloid known for its pharmaceutical activities. However, the role of liensinine in mitigating APAP-induced liver injury remains unclear. Objective The aim of the study was to explore the protective effects of liensinine against APAP-induced liver injury. Methods C57BL/6 male mice were treated with a dose of 200 mg/kg N-acetylcysteine or varying doses of liensinine (10 or 20 mg/kg) for seven consecutive days. APAP (400 mg/kg, i.g .) was then administered to induce liver damage for 12 hours. Blood samples and hepatic tissues were collected for further analysis. Liver enzyme levels and histopathological analysis were employed to assess liver injury. RNA-seq was conducted to evaluate the dynamic changes in gene expression. Biochemical assays were used to measure oxidative stress and inflammation, while the TUNEL assay was performed to assess hepatocyte apoptosis. Results The results demonstrated that the administration of liensinine mitigated serum liver enzyme levels and tissue damage resulting from APAP overdose. Transcriptome analysis revealed significant and coordinated changes in genes related to the peroxisome proliferator-activated receptor signaling pathway, mitogen-activated protein kinase signaling pathway, and apoptosis pathway in response to APAP-induced hepatotoxicity. The expression alterations of key genes within these three pathways, associated with inflammation, oxidative stress, and cell apoptosis, were reversed by liensinine, indicating its potential in alleviating APAP-induced liver damage through multiple signaling pathways. This suggests the diverse therapeutic effects of liensinine, including inflammation suppression, oxidative stress reduction, and cell apoptosis inhibition. Indeed, pretreatment with liensinine effectively reduced inflammatory cytokines, oxidative stress indicators, and apoptotic cells induced by APAP. Conclusions Liensinine mitigates APAP-induced hepatotoxicity in mice through multifaceted pathways, providing anti-inflammatory, antioxidant, and anti-apoptotic benefits.

Polyphyllins are the active ingredients of the medicinal plant Paris polyphylla. The biosynthesis of different types of polyphyllins all require the catalysis of glycosyltransferases. Even though significant efforts have been made to identify PpUGTs capable of catalyzing the initial glycosylation reaction, the specific glycosyltransferases responsible for the synthesis of trillin have not been reported in P. polyphylla. Here, we identified a new trillin synthase, named PpUGT91BP1, which was highly expressed in the rhizome. Importantly, PpUGT91BP1 could specifically glycosylate diosgenin but not pennogenin. To improve its catalytic efficiency, we introduced random mutations through error-prone PCR and conducted an activity-based screening. Three mutants with significantly enhanced trillin synthase activity were identified. Finally, we successfully reconstituted trillin biosynthesis in Nicotiana benthamiana, achieving a yield of 3.69 mg per gram of plant dry weight using the mutant PpUGT91BP1. Taken together, our results deepen the understanding of PpUGT91 family’s role in polyphyllin biosynthesis in P. polyphylla, facilitating rational selection of better P. polyphylla cultivars and guiding future studies in metabolic engineering of polyphllins.

Stress on the Endoplasmic reticulum (ER) can severely disrupt cellular function by impairing protein folding and post-translational modifications, thereby leading to the accumulation of poor-quality proteins. However, research on its impact on photosynthesis remains limited. In this study, we investigated the impact of ER stress on the photosynthetic efficiency of Chlamydomonas reinhardtii using pharmacological inducers, tunicamycin (TM) and brefeldin A (BFA), which specifically target the ER. Our measurements of photosynthetic parameters showed that these ER stress-inducing compounds caused a significant decline in photosynthetic efficiency. A proteomic analysis confirmed that TM and BFA effectively induce ER stress, as evidenced by the upregulation of ER stress-related proteins. Furthermore, we observed a widespread downregulation of photosynthesis-related proteins, which is consistent with the results obtained from our measurements of photosynthetic parameters. These findings suggest that the stress on ER has a profound impact on chloroplast function, disrupting photosynthetic processes. This study highlights the critical interdependence between the ER and chloroplasts, and it underscores the broader implications of ER stress on the cellular metabolism and energy efficiency of photosynthetic organisms.