Acptp2,3 participates in the regulation of spore production, stress response, and pigments synthesis in Aspergillus cirstatus

Aspergillus cristatus was a filamentous fungus that produced sexual spores under hypotonic stress and asexual spores under hypertonic stress. It could be useful for understanding filamentous fungi's sporulation mechanism. Previously, we conducted functional studies on Achog1, which regulated the hyperosmotic glycerol signaling (HOG) pathway and found that SI65_02513 was significantly downregulated in the transcriptomics data of ΔAchog1 knockout strain. This gene was located at multiple locations in the HOG pathway, indicating that it might play an important role in the HOG pathway of A. cristatus. Furthermore, the function of this gene had not been identified in Aspergillus fungi, necessitating further investigation. This gene's conserved domain study revealed that it has the same protein tyrosine phosphatases (PTPs) functional domain as Saccharomyces cerevisiae, hence SI65_02513 was named Acptp2,3.

According to our findings, Acptp2,3 played an important role in the regulation of sporulation, stress response, and pigments synthesis in A. cristatus. This was the first study on the function of PTPs in Aspergillus fungi.

The function of this gene was mostly validated using gene knockout and gene complementation approaches. Knockout strains exhibited sexual and asexual development, as well as pigments synthesis. Morphological observations of the knockout strain were carried out under several stress conditions (osmotic stress, oxidative stress, Congo Red, and sodium dodecyl sulfate (SDS). Real-time fluorescence polymerase chain reaction (PCR) identified the expression of genes involved in sporulation, stress response, and pigments synthesis.

The deletion of Acptp2,3 reduced sexual and asexual spore production by 4.4 and 4.6 times, demonstrating that Acptp2,3 positively regulated the sporulation of A. cristatus. The sensitivity tests to osmotic stress revealed that ΔAcptp2,3 strains did not respond to sorbitol-induced osmotic stress. However, ΔAcptp2.3 strains grew considerably slower than the wild type in high concentration sucrose medium. The ΔAcptp2,3 strains grew slower than the wild type on media containing hydrogen peroxide, Congo red, and SDS. These findings showed that Acptp2,3 favorably controlled osmotic stress, oxidative stress, and cell wall-damaging chemical stress in A. cristatus. Deleting Acptp2,3 resulted in a deeper colony color, demonstrating that Apctp2,3 regulated pigment synthesis in A. cistatus. The expression levels of numerous stress-and pigments-related genes matched the phenotypic data.