Differential expression analysis of sugar accumulation-related genes during chestnut nut development

The chestnuts of Castanea mollissima Bl. are an important food crop in China, and have high nutritional content. To understand the pattern of sugar accumulation during chestnut nut development, the related enzyme gene regulatory pathways, and the molecular regulatory mechanisms of chestnut sugar biosynthesis metabolism, two chestnut varieties with different sugar content, namely Chengbu Youzhu (hereinafter referred to as CBYZ) and AnYou No. 1 (hereinafter referred to as AY01), were selected for investigation. Total sugar and starch content, and the activity of enzymes related to sugar accumulation, were measured in the nuts of the two chestnut varieties 10 days after flowering (DAF), 20 DAF, 30 DAF, 40 DAF, 50 DAF, 60 DAF, 70 DAF, 80 DAF, and 90 DAF. Changes in starch, straight-chain starch, and branched-chain starch content, and sucrose-phosphate synthase, soluble starch synthase, and granule-bound starch synthase enzyme activities were consistent with one-another. A total of 24 differentially expressed genes between the two varieties were associated with sugar biosynthesis and metabolism at three key stages (30, 60, and 90 DAF) of sugar accumulation. Further analysis showing upregulation of the expression of starch-related genes, such as β-amylase, GYS, and INV indicated that these genes were not actively expressed in AY01, resulting in slow accumulation of starch and reduced sugar content. By contrast, the downregulation of the expression of genes, such as PGK and MDH1, indicated that these genes were actively expressed in low-sugar chestnuts, resulting in the rapid fermentation of sugars. A link between gene up- or down-regulation during different developmental stages of chestnut and the effect of their expression on sugar content were established by KEGG pathway enrichment analysis. These findings provide further insights into the mechanism of sugar biosynthesis in chestnuts.

Chestnuts in Fermented Rice Beverages Increase Metabolite Diversity and Antioxidant Activity While Reducing Cellular Oxidative Damage

Foods containing chestnuts (Castanea mollissima Blume) are relatively uncommon, despite the high nutrient and starch contents and purported health benefits. In this study, we examine the flavor-related metabolites, volatile compounds, and amino acids in a traditional glutinous rice fermented beverage supplemented with chestnuts as a fermentation substrate for lactic acid bacteria (LAB). Changes in antioxidant activity towards free radicals and effects on cellular oxidative stress are compared between beverages with or without chestnuts. The fermented chestnut-rice beverage (FCRB) has higher sensory scores and a wider range of volatiles and flavor-related compounds (74 vs. 38 species compounds), but lower amino acid contents, than the traditional fermented glutinous rice beverage (TFRB). In free radical scavenging assays, the FCRB exhibits higher activity than the TFRB in vitro. Furthermore, while neither beverage induces cytotoxity in Caco-2 cells at concentrations up to 2 mg/mL, pretreatment with the FCRB results in lower rates of apoptosis and necrosis and higher overall viability in cells with H₂O₂-induced oxidative stress compared to pretreatment with the TFRB. The enhanced reactive oxygen species neutralization in vitro and protection against oxidative damage in cells, coupled with increased diversity of volatiles and flavor-related metabolites of LAB, support the addition of chestnuts to enhance flavor profile and antioxidant properties of fermented functional foods.

Enzymes and Biocatalysis

Enzymes, also known as biocatalysts, are proteins produced by living cells and found in a wide range of species, including animals, plants, and microorganisms [...]