Survival factor SvfA plays multiple roles in differentiation and is essential for completion of sexual development in Aspergillus nidulans

Abstract

The first member of the velvet family of proteins, VeA, regulates sexual development and secondary metabolism in the filamentous fungus Aspergillus nidulans. in our study, through comparative proteome analysis using wild type and veA-deletion strains, new putative regulators of sexual development were identified and functionally analyzed. Among these, SvfA, containing a yeast survival factor 1 domain, plays multiple roles in the growth and differentiation of A. nidulans. Deletion of the svfA gene resulted in increased sensitivity to oxidative and cold stress as in yeast. the svfAdeletion strain showed an increase in bi-polar germination and a decrease in radial growth rate. The deletion strain formed structurally abnormal conidiophores and thus produced lower amounts of conidiospores during asexual development. the svfA-deletion strain produced few Hülle cells and small cleistothecia with no ascospores, indicating the requirement of svfA for the completion of sexual development. transcription and genetic analyses indicated that SvfA modulates the expression of key development regulatory genes. Western blot analysis revealed two forms of SvfA. The larger form showed sexual-specific and VeA-dependent production. Also, the deletion of svfA caused decreased St (sterigmatocystin) production. We propose that SvfA is a novel central regulator of growth, differentiation and secondary metabolism in A. nidulans. Aspergillus nidulans is a model filamentous fungus that belongs to the phylum Ascomycota. Both asexual and sexual cycles allow the study of various cellular events such as development, stress responses, and secondary metabolism 1-4. Asexual development proceeds in multiple steps with special organs: a foot cell, stalk, vesicle, metulae, phialides, and conidiospores 5. While the vegetative cell goes through asexual development under light conditions, sexual development is favored under dark and hypoxic conditions 6. In the sexual reproductive organ, cleistothecium, numerous asci containing eight red-purple ascospores are developed 1,7,8. The velvet family proteins, including VeA, VelB, VelC, and VosA, comprise highly conserved fungal specific regulators in ascomycetes and basidiomycetes 9. This superfamily plays critical roles in development and secondary metabolism by forming complexes with multiple interacting partners 4,10-12. VeA, the first identified protein in this family, controls the asexual or sexual development in response to external signals such as light and air. This regulatory function of VeA is dependent on its localization. Under light conditions, VeA disperses in both the cytoplasm and the nuclei. Under dark conditions, the VelB-VeA dimer enters the nucleus with the help of importin α (KapA), and forms a trimeric complex with the global regulator of secondary metabolism, LaeA 4,11,13-15. Sexual development and secondary metabolism are induced by the VelB-VeA-LaeA complex and VelC 12. Asexual development is inhibited by the VosA homodimer 9. However, the presence of light blocks the entry of VelB-VeA...

The LAMMER Kinase, LkhA, Affects Aspergillus fumigatus Pathogenicity by Modulating Reproduction and Biosynthesis of Cell Wall PAMPs

“…For mycelial production, strains were cultivated in liquid complete medium (YCGMM), which was the GMM supplemented with 0.15% yeast extract and 0.15% casamino acid. To observe conidiophores, conidia were inoculated on solid YCGMM agar blocks and coverslip-cultured for 24 hrs ( Lim et al., 2020a ). To induce sexual development, the vegetative mass mating (VeM) method was used ( Lim and Park, 2019a ).…”

Survival Factor A (SvfA) Contributes to Aspergillus nidulans Pathogenicity

“…A. nidulans wild-type (WT), svfA -deletion (Δ svfA ), and complementary (C’ svfA ) strains were obtained from our previous studies and maintained in Aspergillus glucose minimal medium (GMM) [ 26 , 34 ]. The C’ svfA strain was generated by the re-introduction of the svfA gene to the Δ svfA strain [ 26 ].…”

“…In a previous study, we identified SvfA as a global transcription factor VeA-dependent protein that has only one domain: a yeast survival factor1 (Svf1) homologous protein. SvfA plays a role in the growth and development of A. nidulans ; it regulates vegetative growth, functions in oxidative and cold stress responses, and affects conidial germination, conidial production, and completion of sexual development [ 26 ]. A. nidulans can produce two forms of the SvfA protein; only the production of the larger form is sexual-development-specific [ 26 ].…”

“…SvfA plays a role in the growth and development of A. nidulans ; it regulates vegetative growth, functions in oxidative and cold stress responses, and affects conidial germination, conidial production, and completion of sexual development [ 26 ]. A. nidulans can produce two forms of the SvfA protein; only the production of the larger form is sexual-development-specific [ 26 ]. In Saccharomyces cerevisiae , the survival factor, functionally complemented by expression of mammalian B-cell lymphoma-extra large (Bcl-x L ), inhibits reactive oxygen species generation and promotes survival under stress conditions [ 27 , 28 ].…”

“…To investigate the cellular function of SvfA on fungal virulence in A. nidulans , we investigated the immune response of alveolar macrophages (AMs) to conidia, biofilm formation ability, protease activity, and relative mRNA transcript levels involved in these cellular mechanisms using previously constructed svfA -deletion and -overexpression strains [ 26 ]. In addition, we reported the virulence of genetically engineered SvfA strains in experimental infection with immunodeficient zebrafish ( foxn1 morphant) and CGD mice (gp91 phox-/- mice).…”