External signal–mediated polarized growth in fungi

Abstract

As the majority of fungi are non-motile, polarized growth in response to an external signal enables them to search for nutrients and mating partners, and hence is crucial for survival and proliferation. While the mechanisms underlying polarization in response to external signals has commonalities with polarization during mitotic division during budding and fission growth, the importance of diverse feedback loops regulating external signal mediated polarized growth is likely to be distinct and uniquely adapted to a dynamic environment. Here we highlight recent advances in our understanding of the mechanisms that are crucial for polarity in response to external signals in fungi, with particular focus on the roles of membrane traffic, small GTPases and lipids, as well as the interplay between cell shape and cell growth.

Cdc42 regulates reactive oxygen species production in the pathogenic yeast Candida albicans

“…The effects of Cdc42 on Fre8 activity may also be indirect via a Cdc42 effector. There are numerous downstream targets of Cdc42 that are required for filamentation, including p21 and MAP kinases, formins, and others ( 22 ), and Fre8 NOX may fall under control of one of these effectors. Since Cdc42 control of Fre8 NOX is clearly post-transcriptional, the mechanism involving such effectors would be distinct from the recently reported transcriptional control of S. cerevsiae Yno1 NOX by MAP kinase pathways ( 46 ).…”

“…C. albicans also expresses a Rac1 Rho GTPase that participates in a distinct cell polarization pathway associated with substrate invasion ( 21 ). As with metazoans, yeast Rho GTPases control cell polarity through numerous effector proteins and kinase signaling pathways ( 15 , 16 , 22 ). However, NOX is not a known effector of Rho GTPases in yeasts.…”

Engineering membrane asymmetry to increase medium‐chain fatty acid tolerance in Saccharomyces cerevisiae

“…The asymmetric distribution of PE in the plasma membrane improved the membrane potential, which was key to improving membrane integrity. Membrane potential is important for various physiological functions, such as biofilm formation (Qin et al, 2019), polarized growth (Bassilana et al, 2020), cellular proliferation (Stratford et al, 2019), and cell viability (Arjes et al, 2020). The engineering of ion channels and the reconstruction of anionic phospholipids are the most common strategies for tuning the membrane potential.…”

Ultrastructural Study of Cryptococcus neoformans Surface During Budding Events

“…Likewise, PCG in fungi occurs by inserting new material into the plasma membrane via the secretory pathways together with concomitant cell wall remodeling. It can be either triggered by internal factors, for example progression of the cell cycle, or by external factors, such as changes in the environment or nutritional status (Bassilana et al, 2020). Although filamentous fungi and yeasts show obvious differences in their growth modes, they share three basic properties that allow for PCG and the formation of a diverse variety of cellular forms: (i) symmetry breaking, in which an initially isotropic cell generates a polarized growth axis, (ii) maintenance of polarity, which refers to the stabilization of the polarity axis so that polar growth is maintained, and finally, (iii) depolarization, in which polarity is lost in a controlled manner.…”