Central South University of Forestry & Technology

Given the vital nutritional and metabolic role of ascorbic acid (AA) and the need for rapid detection, a photoresponsive nanozyme-based composite was developed for sensitive, accurate, and convenient AA analysis. In this report, a ternary ZIF-8/g-C₃N₄/SiO₂ photoresponsive oxidase-mimicking system was developed and applied to AA detection. By regulating the loading ratio of ZIF-8 on the g-C₃N₄/SiO₂ substrate, the composite with excellent photoresponsive oxidase-like activity was successfully prepared. Owing to its enhanced visible-light absorption and efficient charge separation and transfer, the system exhibited significantly improved photoresponsive performance. Experimental results demonstrated that ZIF-8/g-C₃N₄/SiO₂ could catalyze the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), generating oxidized TMB (oxTMB) through the formation of reactive species, thereby producing a distinct color change. In an acidic environment, AA inhibited the oxidase-like activity of the catalyst due to its strong reducing capability, thus suppressing the colorimetric reaction. Based on this principle, the as-synthesized ZIF-8/g-C₃N₄/SiO₂ photoresponsive oxidase mimic was applied to the detection of AA in three beverages. The method revealed a good linear response within the concentration range of 1-40 μM, and the detection limit (LOD) was 0.14 μM. The recoveries of the spiked samples ranged from 95.00% to 103.85%, suggesting that the present method could be successfully applied to sense AA in practical samples. Furthermore, we integrated ZIF-8/g-C₃N₄/SiO₂ with the RGB strategy into a novel sensing platform for the visual/onsite semi-quantitative detection of AA in real samples, demonstrating the great potential prospects for the development of rapid food assay.

Myrcene is a high-value monoterpene extensively applied in the fragrance, flavor, and agricultural industries, yet its efficient microbial production remains challenging due to pathway competition and limited metabolic flux. Compartmentalization offers a unique strategy to spatially organize heterologous metabolic pathways in Saccharomyces cerevisiae, enabling improved pathway efficiency through physical separation from competing cytosolic metabolism. In this study, we engineered the S. cerevisiae nucleus as a synthetic metabolic compartment for myrcene biosynthesis. Screening of myrcene synthases identified two highly active enzymes from Snapdragon Oc15 and Picea abies that function efficiently in S. cerevisiae. Myrcene production was detected only when myrcene synthase and the engineered GPP synthase mERG20p were co-localized to the nucleus, whereas cytosolic expression failed to yield detectable myrcene under their co-expression. Reconstruction of the complete mevalonate (MVA) pathway in the nucleus further increased myrcene titers. By identifying and optimizing rate-limiting steps, we substantially enhanced metabolic flux toward myrcene, achieving a final titer of 23.4 mg L^-1 in flask-shaking fermentation. This work demonstrates the feasibility of repurposing the yeast nucleus for myrcene efficient biosynthesis and provide a new strategy for further improving microbial production of myrcene.

Camellia oleifera is an important economic woody oil plant in many Asian countries, and the anthracnose caused by Colletotrichum fructicola is prevalent in its cultivation regions, causing significant losses annually. We previously found that CfGcn5-mediated H3 acetylation governs virulence of C. fructicola. To further elucidate the regulatory mechanism of CfGcn5, we carried out mass spectrometry analysis for CfGcn5-interacting proteins and identified CfAda3 protein for functional analysis. We found that CfAda3 was mainly localized in nucleus and cooperated with CfGcn5 to acetylate H3K18 for global gene transcription. Targeted gene deletion revealed that CfAda3 is involved in growth and conidiation. Similar to ΔCfgcn5 mutant, the ΔCfada3 mutant is defective in conidial germination, appressorial formation, autophagy, and in the response to environmental stresses. These combined effects result in its non-virulence on C. oleifera. In addition, we provided evidence showing that both NLS region and ADA3 domain are required for the localization and function of CfAda3. Moreover, we indicated that the interaction with CfGcn5 is essential but not sufficient for the normal localization and full function of CfAda3. Taken together, our studies not only illustrate the prominent roles of CfAda3 in growth, development, and virulence but also highlight how CfAda3 functions together with CfGcn5 in C. fructicola.