| Summary: | Ochratoxin A (OTA), as a common mycotoxin, has seriously harmful effects on agricultural products, livestock and humans. There are reports on the regulation of SakA in the MAPK pathway, which regulates the production of mycotoxins. However, the role of SakA in the regulation of <i>Aspergillus westerdijkiae</i> and OTA production is not clear. In this study, a <i>SakA</i> deletion mutant (<i>ΔAwSakA</i>) was constructed. The effects of different concentrations of D-sorbitol, NaCl, Congo red and H<sub>2</sub>O<sub>2</sub> on the mycelia growth, conidia production and biosynthesis of OTA were investigated in <i>A. westerdijkiae</i> WT and <i>ΔAwSakA</i>. The results showed that 100 g/L NaCl and 3.6 M D-sorbitol significantly inhibited mycelium growth and that a concentration of 0.1% Congo red was sufficient to inhibit the mycelium growth. A reduction in mycelium development was observed in <i>ΔAwSakA</i>, especially in high concentrations of osmotic stress. A lack of <i>AwSakA</i> dramatically reduced OTA production by downregulating the expression of the biosynthetic genes <i>otaA</i>, <i>otaY</i>, <i>otaB</i> and <i>otaD</i>. However, <i>otaC</i> and the transcription factor <i>otaR</i>1 were slightly upregulated by 80 g/L NaCl and 2.4 M D-sorbitol, whereas they were downregulated by 0.1% Congo red and 2 mM H<sub>2</sub>O<sub>2</sub>. Furthermore, <i>ΔAwSakA</i> showed degenerative infection ability toward pears and grapes. These results suggest that <i>AwSakA</i> is involved in the regulation of fungal growth, OTA biosynthesis and the pathogenicity of <i>A. westerdijkiae</i> and could be influenced by specific environmental stresses.
|
|---|