AUTHOR=Xie Xiang-Li , Wei Yi , Song Yan-Yue , Pan Guan-Ming , Chen Li-Na , Wang Gang , Zhang Shi-Hong 

TITLE=Genetic Analysis of Four Sexual Differentiation Process Proteins (isp4/SDPs) in Chaetomium thermophilum and Thermomyces lanuginosus Reveals Their Distinct Roles in Development

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02994

DOI=10.3389/fmicb.2019.02994

ISSN=1664-302X

ABSTRACT=<p>Fungal sexual development requires the involvement of a large number of functional genes. Fungal genes encoding sexual differentiation process proteins (<italic>SDPs</italic>), <italic>isps</italic>, have been known for decades. <italic>isp4</italic>/<italic>SDP</italic> and its homologs function as oligopeptide transporters (OPTs), yet their roles in reproduction are unknown. Here, we genetically analyzed all four <italic>isp4/SDP</italic> homologs in the sexual species <italic>Chaetomium thermophilum</italic> and asexual species <italic>Thermomyces lanuginosus.</italic> Using single gene deletion mutants, we found that <italic>T. lanuginosus SDP</italic> (<italic>TlSDP</italic>) participated in asexual sporulation, whereas the other homologs participated in sexual morphogenesis. In complementary tests, <italic>C. thermophilum SDPs (CtSDP1</italic>-<italic>3)</italic> restored sporulation defects in <italic>TlSDP</italic> deletion strains (Δ<italic>TlSDP</italic>), and their translated proteins, which were localized onto the cytomembrane, possessed OPT activity. Interestingly, <italic>CtSDP2</italic> accumulated at the top of the hyphae played a distinct role in determining the sexual cycle, glutathione transport, and lifespan shortening. A unique 72nt-insertion fragment (72INS) was discovered in <italic>CtSDP2</italic>. Biological analysis of the 72INS deletion and DsRED-tagged fusion strains implied the involvement of 72INS in fungal growth and development. In contrast to <italic>TlSDP</italic>, which only contributes to conidial production, the three <italic>CtSDP</italic>s play important roles in sexual and asexual reproduction, and <italic>CtSDP2</italic> harbors a unique functional 72INS that initiates sexual morphogenesis.</p>