New Aspects of Invasive Growth Regulation Identified by Functional Profiling of MAPK Pathway Targets in Saccharomyces cerevisiae

Abstract

MAPK pathways are drivers of morphogenesis and stress response in eukaryotes. A major function of MAPK pathways is the transcriptional induction of target genes, which produce proteins that collectively generate a cellular response. One approach to comprehensively understand how MAPK pathways regulate cellular responses is to characterize the individual functions of their transcriptional targets. Here, by examining uncharacterized targets of the MAPK pathway that positively regulates filamentous growth in Saccharomyces cerevisiae (fMAPK pathway), we identified a new role for the pathway in negatively regulating invasive growth. Specifically, four targets were identified that had an inhibitory role in invasive growth: RPI1, RGD2, TIP1, and NFG1/YLR042c. NFG1 was a highly induced unknown open reading frame that Negatively regulated the Filamentous Growth MAPK pathway. We also identified SFG1, which encodes a transcription factor, as a target of the fMAPK pathway. Sfg1p promoted cell adhesion independently from the fMAPK pathway target and major cell adhesion flocculin Flo11p, by repressing genes encoding presumptive cell wall degrading enzymes. Sfg1p also contributed to FLO11 expression. Sfg1p and Flo11p regulated different aspects of cell adhesion, and their roles varied based on the environment. Sfg1p also induced an elongated cell morphology, presumably through a cell-cycle delay. Thus, the fMAPK pathway coordinates positive and negative regulatory proteins to fine-tune filamentous growth resulting in a nuanced response. Functional analysis of other pathways' targets may lead to a more comprehensive understanding of how signaling cascades generate biological responses.

Spatiotemporal Control of Pathway Sensors and Cross-Pathway Feedback Regulate a Cell Differentiation MAPK Pathway in Yeast

“…2A , Clb2-HA, STE11-4 αf 2h), which is suggestive of a delay in G1 arrest. The delay might result from elevated fMAPK activity, which delays the cell cycle in G1 (L oeb et al 1999; M adhani et al 1999) and G2/M (A hn et al 1999; R ua et al 2001; V andermeulen and C ullen 2020). In line with this possibility, cells containing Ste11p-4 also showed a delay in accumulation in Clb2p-HA ( Fig.…”

“…The cell-cycle regulation of the fMAPK pathway might extend to transcriptional targets of the pathway. The fMAPK pathway regulates multiple target genes that encode proteins that bring about filamentous growth (M adhani et al 1999; R oberts et al 2000; V andermeulen and C ullen 2020). A major target of the fMAPK pathway is the gene encoding the cell adhesion molecule Flo11p (R upp et al 1999; V inod et al 2008), which promotes cell adhesion during filamentous/invasive growth (R upp et al 1999).…”

“…Cell synchronization by elutriation (R osebrock 2017) was not feasible for cells of the ∑1278b background because cells fail to separate, even those lacking the adhesion molecule Flo11p (V andermeulen and C ullen 2020). Cell synchronization experiments were performed as previously described (B reeden 1997; P rabhakar et al 2020).…”

Deletion of the MBP1 Gene, Involved in the Cell Cycle, Affects Respiration and Pseudohyphal Differentiation in Saccharomyces cerevisiae

“…First, deletion of genes, involved in the cell cycle and regulated by MBF, cause abnormal budding ( 33 ). Second, MAPK induces cell elongation by regulating CLN1 ( 34 ), a gene essential for pseudohyphal growth ( 35 , 36 ). In addition, there is some interaction between MBP1 and CLN1 ( 37 ).…”

“…Filamentous growth is a behavior more complex and globally regulated than is currently appreciated ( 32 ) and is regulated by MAPK pathways both positively and negatively ( 34 ). Cross talk among filamentous growth (FG) and other MAPK pathways, such as the pheromone response ( 32 , 41 , 42 ) and the high-osmolarity glycerol ( 32 , 42 ), have been reported.…”