Functional Differentiation And Association Of The FgPho23 And FgPho23 Like Proteins In Fusarium Graminearum

Fusarium head blight(FHB)is a major fungal disease that seriously affects grain production and food safety in China,among which Fusarium graminearum is the dominant pathogen.It is of great significance to fully understand the mechanism of F.graminearum growth,development and pathogenicity for the development of FHB control strategy.Histone acetylation is an important epigenetic modification which plays an important role in every stage of pathogen life cycle.The level of histone acetylation is regulated by acetyltransferase and deacetylase complex.The activation of catalytic subunits in both complexes depend on the presence of non-catalytic subunits.As an important class of tumor suppressors,the growth inhibitory factor protein family(ING)is considered to be a key component of the histone acetylation and deacetylation complex,which is involved in the regulation of histone acetylation.Previous studies have analyzed the function of ING protein FNG1 in F.graminearum.In this study,we identified two other ING proteins,FgPho23 and FgPho23 like,and studied their function,localization and molecular mechanism.The deletion mutants of FgPHO23 and FgPHO23 LIKE were obtained by split-PCR and PEG-mediated protoplast transformation.We found Fgpho23 and Fgpho23 like mutants grew slowly and significantly reduced pathogenicity,suggesting that both genes are important for growth and infection.Both of them had significant functional differentiation in regulating biological processes such as morphogenesis of aerial hyphae,sexual development and autophagy.The PHD domain is responsible for recognizing histone methylation existing in the carbon terminal of FgPho23 and FgPho23 like proteins.We interchanged the PHD domain of FgPho23 and FgPho23 like proteins,and found that the function of the two proteins was not affected.Therefore,we speculated that the cause of functional differentiation between the two genes is unrelated to PHD domain.Based on subcellular localization observation of FgPho23 and FgPho23 like,we found that although both of them were localized in the nucleus,there were significant difference.FgPho23 completely co-localizes with Fg Rpd3,the catalytic subunit of Rpd3 histone deacetylation complex,while FgPho23 like only partially co-localizes with Fg Rpd3.Histone acetylation level analysis showed that the acetylation levels of histone H3 and H4 increased in the Fgpho23 mutant,while only the acetylation level of H4 increased in the Fgpho23 like mutant,while the acetylation level of H3 decreased.This suggests that FgPho23 like is involved in the positive regulation of H3 acetylation.Therefore,we speculated that FgPho23 like may be associated with the Nu A3 complex responsible for H3 acetylation.Further Bi FC assays confirmed that FgPho23 like protein not only interacts with Fg Rpd3,but also Fg Sas3,the catalytic subunit of Nu A3 complex.In addition,FgPho23 like also maintains the stability of Fg Sas3 protein and participates in Nu A3 complex recognition of H3K4me3.FgPho23,another ING protein of F.graminearum,only interacts with Fg Rpd3.These results suggest that the association with different complexes determines the functional differentiation between FgPho23 and FgPho23 like.Further analysis of RNA-seq data showed that there were a large amount of overlap among the genes regulated by FgPho23 like,Fg Sas3 and Fg Rpd3,which further confirmed the close relationship between FgPho23 like and the two complexes in regulating gene transcription.In conclusion,the growth inhibitory factors FgPho23 and FgPho23 like regulate the level of histone acetylation and gene transcription mode through association with the Rpd3 histone deacetylation complex and Nu A3 histone acetylation complex,thus playing key roles in the growth,development and infection process of F.graminearum.The functional analysis of F.graminearum ING protein plays an important foundation for revealing the regulatory network of fungal histone modification.