ASF1 regulates asexual and sexual reproduction in Stemphylium eturmiunum by DJ-1 stimulation of PI3K/AKT signaling pathway

Abstract

Most fungi display a mixed mating system with both asexual and sexual reproduction. The timing of the two modes of reproduction must be carefully coordinated through signal perception and coordination in the cell along with chromatin modification. Here, we investigated coordination of reproductive output by investigating the function of the histone chaperone anti-silencing factor 1 (ASF1) in a fungal species amenable to characterization of both asexual and sexual reproduction. We used knockout approach to show that SeASF1 influenced asexual and sexual reproduction in S. eturmiunum. SeASF1-deleted strains failed to produce perithecia, but produce abnormal conidia and showed an irregular distribution of nuclei in mycelium. Transcriptome sequencing was then used to identify genes with altered expression in the SeASF1-deleted strains. The screen identified SeDJ-1 that was strongly regulated by SeASF1. The interaction of SeDJ-1 and SeASF1 was confirmed using Y2H, Co-IP, and pull-down. The phosphatidylinositol 3kinase/protein kinase B (PI3K/AKT) signaling pathway was known to interact with DJ-1 in mammals, and we verified that SePI3K was directly linked to SeDJ-1 and was defined as a coordinator of reproduction. Meanwhile, SeDJ-1 and SePI3K stimulated asexual and sexual activity, respectively, but SePI3K recovered the asexual and sexual development of SeDJ-1 knockout mutants. The SeDJ-1-M6 segment of SeDJ-1 was essential for its interaction with SePI3K and also carried out a critical role in restoring reproduction in the SePI3K knockout mutants, providing a deep understanding of the regulatory mechanism of SeDJ-1 in S. eturmiunum. Summarily, SeASF1 triggers SeDJ-1 to activate SePI3K which is involved in asexual and sexual reproduction in S. eturmiunum. This study revealed that SeASF1 manipulates asexual and sexual reproduction in S. eturmiunum by SeDJ-1 perception of PI3K/AKT signaling pathway. These data highlight the deep similarities in coordinating asexual and sexual processes in both fungi and eukaryotes in general.