Pyruvate decarboxylase and its lysine succinylation contribute to the development and metabolite biosynthesis in pathogenic fungus <i>Aspergillus flavus</i>

This study evaluates the effects of pyruvate decarboxylase and its lysine succinylation (Ksucc) on the development of <i>Aspergillus flavus</i> and the production of secondary metabolites. Mutant strains, including the knockout (∆<i>pdc1</i>), <i>pdc1</i> point mutants (K258R and K258E) and complementary (∆<i>pdc1.com</i>) were constructed. The results showed that both Δ<i>pdc1</i> and K258R strains exhibited decreased conidiophore and conidia production and failed to generate sclerotia. The production of aflatoxin B1 (AFB1) was significantly increased in the Δ<i>pdc1</i> and K258R strains, while it decreased in the K258E strain. The results also indicate that <i>pdc1</i> and its Ksucc are involved in the stress response and pathogenicity of <i>A. flavus</i>. Through GC-MS analysis, Δ<i>pdc1</i> was found to produce several significantly decreased compounds, including n-hexadecanoic acid, 2-bromotetradecane, and palmitic acid, among others. Additionally, different volatile metabolites, such as 1-iodo-decane, <i>n</i>, <i>n</i>-dimethyloctanamide and <i>n</i>, <i>n</i>-dimethyl-7-octynamide, were not detected in the Δ<i>pdc1</i> strain compared to WT and Δ<i>pdc1.com</i>. HPLC results showed that the production of pyruvic acid, malic acid and succinic acid increased in both the Δ<i>pdc1</i> and K258R strains when compared to WT and Δ<i>pdc1.com</i> strains. Comparative RNA-seq analysis revealed a total of 3,817 differentially expressed genes (DEGs) including 1,913 up-regulated and 1,904 down-regulated genes in Δ<i>pdc1 vs</i>. WT. These results suggest that PDC1 and K258 play a crucial role in the biosynthesis of secondary metabolites, development and stress responses of <i>A. flavus</i>.