Muc1, a mucin-like protein that is regulated by Mss10, is critical for pseudohyphal differentiation in yeast.

Abstract

Pseudohyphal differentiation in Saccharomyces cerevisiae was first described as a response of diploid cells to nitrogen limitation. Here we report that haploid and diploid starch-degrading S. cerevisiae strains were able to switch from a yeast form to a filamentous pseudohyphal form in response to carbon limitation in the presence of an ample supply of nitrogen. Two genes, MSSIO and MUCI, were cloned and shown to be involved in pseudohyphal differentiation and invasive growth. The deletion of MSSIO resulted in extremely reduced amounts of pseudohyphal differentiation and invasive growth, whereas the deletion of MUCI abolished pseudohyphal differentiation and invasive growth completely. MsslO appears to be a transcriptional activator that responds to nutrient limitation and coregulates the expression of MUCI and the STAI-3 glucoamylase genes, which are involved in starch degradation. MUCI encodes a 1367-amino acid protein, containing several serine/threonine-rich repeats. Mucd is a putative integral membrane-bound protein, similar to mammalian mucin-like membrane proteins that have been implicated to play a role in the ability of cancer cells to invade other tissues.

Architecture and Biosynthesis of the Saccharomyces cerevisiae Cell Wall

“…However, activation of individual FLO genes confers the ability to flocculate (Guo et al 2000;Van Mulders et al 2009). Flo11/Muc1, a diverged Flo protein (Lambrechts et al 1996;Lo and Dranginis 1996), is not involved in flocculation, but is required for pseudohypha formation by diploids, invasion of agar by haploids, and biofilm development (Lo and Dranginis 1998;Guo et al 2000;Reynolds and Fink 2001;Dranginis et al 2007;Bojsen et al 2012).…”

Differential regulation of cell wall biogenesis during growth and development in yeast

“…Both signalling pathways converge on a common important output (Rupp et al, 1999), the GPI-dependent cell wall protein Flo11p, which plays a central role in pseudohyphal growth, and the presence of which is sufficient to induce invasion and frayed colony morphology even in the absence of signalling (Lambrechts et al, 1996 ;Lo & Dranginis, 1998). Yeast mutated for FLO11, which in diploids is transcribed only when nitrogen is limiting, can no longer invade solid media and colonies lose their frayed edges, suggesting that cell elongation or budding pattern might also be affected.…”

Genes with internal repeats require the THO complex for transcription

“…The gene knockout library of S. cerevisiae containing all viable single-gene deletions was screened to identify genes that are required for FLO11 function. FLO11, a gene with many long internal tandem repeats, confers adhesion of cells to inert substrates, such as agar (26,27). The screen used a P TEF FLO11 construct in which the FLO11 gene was transcribed from the constitutive TEF promoter.…”