ASF1 regulates asexual and sexual reproduction in Stemphylium eturmiunum by DJ-1 stimulation of the 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 Stemphylium eturmiunum. SeASF1-deleted strains failed to produce pseudothecia, 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 transcriptional expression of the identified SeDJ-1 was strongly regulated by SeASF1. The interaction of SeDJ-1 and SeASF1 was confirmed using Y2H, Co-IP, and pull-down. Due to some components of phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signaling pathway were known to interact with DJ-1 in mammals, we verified SePI3K, an element of PI3K/AKT signaling pathway in S. eturmiunum, was directly linked to SeDJ-1 and then these two proteins were defined as a coordinator of reproduction. However, knockout of SeDJ-1 or SePI3K altered the asexual and sexual reproduction, but SePI3K recovered the asexual and sexual development of ∆Sedj-1. The SeDJ-1-M6 segment of SeDJ-1 was essential for its interaction with SePI3K and played a critical role in restoring sexual reproduction in the ∆Sepi3k, providing a deep understanding of the regulatory mechanism of SeDJ-1 in S. eturmiunum development. Summarily, SeASF1 is able to trigger SeDJ-1 and SeDJ-1can also activate SePI3K, which is orchestrally involved in asexual and sexual reproduction in S. eturmiunum. All these results reveal 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.