AUTHOR=Brault Ariane , Mbuya Berthy , Labbé Simon 

TITLE=Sib1, Sib2, and Sib3 proteins are required for ferrichrome-mediated cross-feeding interaction between Schizosaccharomyces pombe and Saccharomyces cerevisiae

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.962853

DOI=10.3389/fmicb.2022.962853

ISSN=1664-302X

ABSTRACT=<p>Although <italic>Saccharomyces cerevisiae</italic> is unable to produce siderophores, this fungal organism can assimilate iron bound to the hydroxamate-type siderophore ferrichrome (Fc) produced and secreted by other microbes. Fc can enter <italic>S. cerevisiae</italic> cells <italic>via</italic> Arn1. Unlike <italic>S. cerevisiae</italic>, <italic>Schizosaccharomyces pombe</italic> synthesizes and secretes Fc. The <italic>sib1</italic><sup>+</sup> and <italic>sib2</italic><sup>+</sup> genes encode, respectively, a Fc synthetase and an ornithine-N<sup>5</sup>-oxygenase, which are required for Fc production. When both genes were expressed in <italic>S. pombe</italic>, cross-feeding experiments revealed that <italic>S. cerevisiae fet3</italic>Δ <italic>arn1-4</italic>Δ cells expressing Arn1 could grow in the vicinity of <italic>S. pombe</italic> under low-iron conditions. In contrast, deletion of <italic>sib1</italic><sup>+</sup> and <italic>sib2</italic><sup>+</sup> produced a defect in the ability of <italic>S. pombe</italic> to keep <italic>S. cerevisiae</italic> cells alive when Fc is used as the sole source of iron. Further analysis identified a gene designated <italic>sib3</italic><sup>+</sup> that encodes an N<sup>5</sup>-transacetylase required for Fc production in <italic>S. pombe</italic>. The <italic>sib3</italic>Δ mutant strain exhibited a severe growth defect in iron-poor media, and it was unable to promote Fc-dependent growth of <italic>S. cerevisiae</italic> cells. Microscopic analyses of <italic>S. pombe</italic> cells expressing a functional Sib3-GFP protein revealed that Sib3 was localized throughout the cells, with a proportion of Sib3 being colocalized with Sib1 and Sib2 within the cytosol. Collectively, these results describe the first example of a one-way cross-feeding interaction, with <italic>S. pombe</italic> providing Fc that enables <italic>S. cerevisiae</italic> to grow when Fc is used as the sole source of iron.</p>