Functional Analysis of Penicillium expansum Glucose Oxidase-Encoding Gene, GOX2, and Its Expression Responses to Multiple Environmental Factors

Penicillium expansum is an acidogenic fungal species that belongs to the phylum Ascomycota. During the infection and colonization of host fruits, P. expansum can efficiently express glucose oxidase (GOX) and oxidize β-D-glucose to generate gluconic acid (GLA). In this study, the bioinformatics analysis method was employed to predict and analyze the function of the GOX protein. In addition, a comprehensive assessment was conducted on the P. expansum GOX coding gene GOX2, and the expression response rules of GOX2 under different external stress environments were explored. The results show that GOX is an unstable hydrophilic protein. It is either an integrated membrane protein (such as a receptor or channel) that is directly anchored to the membrane through a transmembrane structure or a non-classical secreted protein that is secreted extracellularly. RNA-seq data analysis shows that the GOX2 gene is regulated by multiple environmental factors, including pH, temperature, carbon base, and chemical fungicides. The expression level of GOX2 reaches its maximum value under alkaline conditions (pH 8–10) and at approximately 10 °C. Using starch as the carbon source and adding sodium propionate or potassium sorbate has the effect of inhibiting the expression of the GOX2 gene. The analysis of the function of the GOX protein and the characteristics of the GOX2 gene in P. expansum provides new insights into the glucose oxidase-encoding gene GOX2. The research results provide significant value for the subsequent development of new disease resistance strategies by targeting the GOX2 gene and reducing post-harvest disease losses in fruits.