Cheng Wang

Rapamycin is a polyketide macrocyclic antibiotic with exceptional pharmacological potential. To explore the potential mechanism of rapamycin overproduction, the intracellular metabolic differences of three chemical elicitor treatments were first investigated by combining them with dynamic metabolomics and network analysis. The metabolic response characteristics of each chemical elicitor treatment were identified by a weighted gene co-expression network analysis (WGCNA) model. According to the analysis of the identified metabolic modules, the changes in the cell membrane permeability might play a key role in rapamycin overproduction for dimethyl sulfoxide (DMSO) treatment. The enhancement of the starter unit of 4,5-dihydroxycyclohex-1-ene carboxylic acid (DHCHC) and the nicotinamide adenine dinucleotide phosphate (NADPH) availability were the main functions in the LaCl₃ treatment. However, for sodium butyrate (SB), the improvement of the methylmalonyl-CoA and NADPH availability was a potential reason for the rapamycin overproduction. Further, the responsive metabolic pathways after chemical elicitor treatments were selected to predict the potential key limiting steps in rapamycin accumulation using a genome-scale metabolic network model (GSMM). Based on the prediction results, the targets within the reinforcement of the DHCHC and NADPH supply were selected to verify their effects on rapamycin production. The highest rapamycin yield improved 1.62 fold in the HT-aroA/zwf2 strain compared to the control.

As an important medicine homologous food, Chinese jujube is rich in nutrition and medicinal value. To enhance the bioactive compounds level of Chinese jujube products, three kinds of fungi strains (Rhizopus oryzae, Aspergillus niger and Monascus purpureus) were firstly selected to evaluate their effects on total soluble phenolic compounds (TSPC) and total soluble flavonoids compounds (TSFC) contents during liquid state fermentation of Chinese jujube. As the best strain, the highest contents of TSPC and TSFC could increase by 102.1% (26.02 mg GAE/g DW) and 722.8% (18.76 mg RE/g DW) under M. purpureus fermentation when compared to the unfermented sample, respectively. Qualitative and quantitative analysis of individual polyphenol compounds indicated that proto-catechuic acid, p-hydroxybenzoic acid and chlorogenic acid showed the highest level in the fer-mented Chinese jujube at the 7th day, which was enhanced by 16.72-, 14.05- and 6.03-fold when compared to the control, respectively. Combining with RNA sequencing, function annotation of CAZymes database and polyphenol profiling, three potential transformation pathways of poly-phenol compounds were proposed in the fermented Chinese jujube by M. purpureus, such as the conversion of insoluble bound phenolic acids, rutin and anthocyanin degradation. These findings would be beneficial for better understanding of the biotransformation mechanism of polyphenol compounds in fungi fermentation.

Pericarp color is an important economic characteristic of Zanthoxylum bungeanum. Anthocyanins are the main reason for the pericarp’s red appearance in Z. bungeanum. In this study, through the combined analysis of the metabolome and transcriptome, HY5, whose expression is highly correlated to changes in the anthocyanin content, was screened and identified. Under natural ripening conditions, the Z. bungeanum fruit gradually changed in color from green to red, while bagging resulted in the fruit maintaining its green color. After unbagging, the fruit gradually turned red, and the ZbHY5 expression and anthocyanin content increased. In addition, the leaves changed from green to red after exposure to UV-B radiation, and the ZbHY5 expression and anthocyanin content increased. The transient overexpression of ZbHY5 deepened the redness of the Z. bungeanum leaves and promoted the expression of ZbHY5 and ZbMYB113 as well as anthocyanin accumulation. Bimolecular fluorescence complementation (BIFC) showed that there was an interaction between ZbHY5 and ZbMYB113. These results revealed that under UV-B irradiation, ZbHY5 might regulate the expression levels of the structural genes related to anthocyanin biosynthesis through combination with ZbMYB113, thereby affecting anthocyanin accumulation. This finding provides useful insights for further studies focusing on UV-B-induced anthocyanin accumulation in Z. bungeanum.