scholarly journals Septins coordinate cell wall integrity and lipid metabolism in a sphingolipid-dependent process

2020 ◽  
Author(s):  
Alexander Mela ◽  
Michelle Momany
Keyword(s):  
Cell Wall ◽  
Mapk Pathway ◽  
Single Agent ◽  
Cell Wall Integrity ◽  
Sphingolipid Metabolism ◽  
Minor Role ◽  
Cell Wall Polysaccharide ◽  
Null Mutant ◽  
A Minor ◽  
Null Mutants

AbstractDuring normal development and response to environmental stress, fungi must coordinate synthesis of the cell wall and plasma membrane. Septins, small cytoskeletal GTPases, colocalize with membrane sterol-rich regions and facilitate recruitment of cell wall synthases during dynamic wall remodeling. In this study we show that null mutants missing an Aspergillus nidulans core septin present in hexamers and octamers (ΔaspAcdc11, ΔaspBcdc3, or ΔaspCcdc12) are sensitive to multiple cell wall-disturbing agents known to activate the cell wall integrity MAPK pathway and that this sensitivity can be remediated by osmotic support. The null mutant missing the octamer-exclusive core septin (ΔaspDcdc10) showed similar osmotic-remedial sensitivity, but only to a single cell wall-disturbing agent and the null mutant missing the noncore septin (ΔaspE) showed very mild osmotic-remedial sensitivity to a different single agent. Representative core septin null mutants showed changes in cell wall polysaccharide composition, organization, and chitin synthase localization. Double mutant analysis with ΔmpkA suggested core septins interact with the cell wall integrity pathway. Null mutants missing any of the five septins were resistant to ergosterol-disrupting agents. The ΔaspAcdc11, ΔaspBcdc3, and ΔaspCcdc12 mutants showed increased sensitivity to sphingolipid-disrupting agents that was remediated by addition of exogenous phytosphingosine. Representative core septins were mislocalized after treatment with sphingolipid-disrupting agents, but not after treatment with ergosterol-disrupting agents. When challenged with both sphingolipid-disturbing and cell wall-disturbing agents in combination, remediation of the lipid defect restored proper growth to ΔaspAcdc11, ΔaspBcdc3, and ΔaspCcdc12, but remediation of the cell wall defect did not. Our data suggest that the core hexamer and octamer septins are involved in cell wall integrity signaling with the noncore septin playing a minor role; that all five septins are involved in monitoring ergosterol metabolism; that the hexamer septins are required for sphingolipid metabolism; and that septins require sphingolipids to coordinate the cell wall integrity response.

scholarly journals Septins coordinate cell wall integrity and lipid metabolism in a sphingolipid-dependent process

2021 ◽  
pp. jcs.258336
Author(s):  
Alexander Mela ◽  
Michelle Momany
Keyword(s):  
Cell Wall ◽  
Mapk Pathway ◽  
Single Agent ◽  
Cell Wall Integrity ◽  
Sphingolipid Metabolism ◽  
Null Mutant ◽  
The Core ◽  
Increased Sensitivity ◽  
Multiple Cell ◽  
Polysaccharide Composition

Septins colocalize with membrane sterol-rich regions and facilitate recruitment of cell wall synthases during wall remodeling. We show that null mutants missing an Aspergillus nidulans core septin present in hexamers and octamers (ΔaspAcdc11, ΔaspBcdc3, or ΔaspCcdc12) are sensitive to multiple cell wall-disturbing agents that activate the cell wall integrity MAPK pathway. The null mutant missing the octamer-exclusive core septin (ΔaspDcdc10) showed similar sensitivity, but only to a single cell wall-disturbing agent and the null mutant missing the noncore septin (ΔaspE) showed very mild sensitivity to a different single agent. Core septin mutants showed changes in wall polysaccharide composition and chitin synthase localization. Mutants missing any of the five septins resisted ergosterol-disrupting agents. Hexamer mutants showed increased sensitivity to sphingolipid-disrupting agents. Core septins mislocalized after treatment with sphingolipid-disrupting agents, but not after ergosterol-disrupting agents. Our data suggest that the core septins are involved in cell wall integrity signaling; that all five septins are involved in monitoring ergosterol metabolism; that the hexamer septins are required for sphingolipid metabolism; and that septins require sphingolipids to coordinate the cell wall integrity response.

scholarly journals Yeast Nap1-Binding Protein Nbp2p Is Required for Mitotic Growth at High Temperatures and for Cell Wall Integrity

Genetics ◽  
2003 ◽  
Vol 165 (2) ◽  
pp. 517-529
Author(s):  
Kentaro Ohkuni ◽  
Asuko Okuda ◽  
Akihiko Kikuchi
Keyword(s):  
Cell Death ◽  
Cell Wall ◽  
High Temperature ◽  
High Temperatures ◽  
Hybrid System ◽  
Mapk Pathway ◽  
Binding Protein ◽  
Cell Wall Integrity ◽  
Calcofluor White ◽  
Two Hybrid

AbstractNbp2p is a Nap1-binding protein in Saccharomyces cerevisiae identified by its interaction with Nap1 by a two-hybrid system. NBP2 encodes a novel protein consisting of 236 amino acids with a Src homology 3 (SH3) domain. We showed that NBP2 functions to promote mitotic cell growth at high temperatures and cell wall integrity. Loss of Nbp2 results in cell death at high temperatures and in sensitivity to calcofluor white. Cell death at high temperature is thought not to be due to a weakened cell wall. Additionally, we have isolated several type-2C serine threonine protein phosphatases (PTCs) as multicopy suppressors and MAP kinase-kinase (MAPKK), related to the yeast PKC MAPK pathway, as deletion suppressors of the nbp2Δ mutant. Screening for deletion suppressors is a new genetic approach to identify and characterize additional proteins in the Nbp2-dependent pathway. Genetic analyses suggested that Ptc1, which interacts with Nbp2 by the two-hybrid system, acts downstream of Nbp2 and that cells lacking the function of Nbp2 prefer to lose Mkk1, but the PKC MAPK pathway itself is indispensable when Nbp2 is deleted at high temperature.

scholarly journals Transcripts repressed at the stop of phloem unloading highlight the energy efficiency of sugar import in the ripening V. vinifera fruit.

2021 ◽  
Author(s):  
Stefania Savoi ◽  
Laurent Torregrosa ◽  
Charles Romieu
Keyword(s):  
Cell Wall ◽  
Regulatory Elements ◽  
Solute Concentration ◽  
Growth Patterns ◽  
Individual Growth ◽  
Sugar Accumulation ◽  
Minor Role ◽  
Phloem Unloading ◽  
Sugar Transporters ◽  
A Minor

AbstractTranscriptomic changes at the cessation of sugar accumulation in the pericarp of Vitis vinifera were addressed on single berries re-synchronized according to their individual growth patterns. The net rates of water, sugars and K+ accumulation inferred from individual growth and solute concentration confirmed that these inflows stopped simultaneously in the ripe berry, while the small amount of malic acid remaining at this stage was still being oxidized at a low rate. Resynchronized individual berries displayed negligible variations in gene expression among triplicates. RNA-Seq studies revealed sharp reprogramming of cell wall enzymes and structural proteins, associated with an 80% repression of specific sugar transporters and aquaporins on the plasma or tonoplast membranes, at the stop of phloem unloading in the three genotypes and two environments investigated. The prevalence of SWEET transporters suggests that electrogenic transporters would just play a minor role on the plasma membrane of SE/CC complex, and the one of the flesh, while sucrose/H+ exchangers dominate on its tonoplast. Cis-regulatory elements present in their promoters allowed to sort these transporters in different groups, also including specific TIPs and PIPs paralogs, and cohorts of cell wall related genes. These results lead us to propose which structural, developmental and energy adaptations would give this fruit such a power of attraction for water and photoassimilates.

Activation of the yeast cell wall integrity MAPK pathway by zymolyase depends on protease and glucanase activities and requires the mucin-like protein Hkr1 but not Msb2

FEBS Letters ◽  
2013 ◽  
Vol 587 (22) ◽  
pp. 3675-3680 ◽  
Author(s):  
José M. Rodríguez-Peña ◽  
Sonia Díez-Muñiz ◽  
Clara Bermejo ◽  
César Nombela ◽  
Javier Arroyo
Keyword(s):  
Cell Wall ◽  
Yeast Cell ◽  
Mapk Pathway ◽  
Cell Wall Integrity ◽  
Yeast Cell Wall

Nuclear behaviour and cell wall composition in relation to budding in mutants of the yeast Saccharomyces cerevisiae

1986 ◽  
Vol 64 (1) ◽  
pp. 193-200 ◽  
Author(s):  
Mario Lachapelle ◽  
E. Roger Boothroyd
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Wall ◽  
Spindle Pole ◽  
Minor Role ◽  
Temperature Sensitive ◽  
Yeast Saccharomyces Cerevisiae ◽  
Bud Emergence ◽  
Spindle Elongation ◽  
10 Nm Filaments ◽  
A Minor

A temperature-sensitive, cell division cycle mutant (cdc24–1) and karyogamy-deficient (kar1) mutant of Saccharomyces cerevisiae, both of which can produce binucleate or multinucleate cells, were used to study certain aspects of budding, after fluorescent staining for mannan, chitin, and nuclei (DNA). In most binucleate cells the two nuclei lay close together and divided into the same bud. In a few, however, the nuclei were far apart and one or two buds were formed, each proximal to a nucleus. The proximity of daughter nuclei in most blocked cdc24–1 cells suggests a role for the CDC24 gene product in spindle elongation. The relationship between the nuclei and the number and location of buds supports the theory of a preponderant role for the nucleus in budding. Although buds develop preferentially in regions of low chitin content in kar1 heterokaryons, the ability of cdc24–1 cells to bud even with a uniformly high content of chitin and mannan suggests a minor role for these cell wall constituents in determining the sites of bud emergence. The chitin ring is not needed for bud emergence but seems to play a role in normal bud development and in septum formation. Electron microscopy of cdc24–1 cells blocked (37 °C) for 8 h and released (23 °C) for 30 min showed morphologically normal spindle pole bodies, cytoplasmic microtubules, and intranuclear spindles. Although the chitin ring was absent, the ring of 10-nm filaments was present, consistent with its proposed role in bud emergence.

scholarly journals The GPI-modified proteins Pga59 and Pga62 of Candida albicans are required for cell wall integrity

Microbiology ◽  
2009 ◽  
Vol 155 (6) ◽  
pp. 2004-2020 ◽  
Author(s):  
Emilia Moreno-Ruiz ◽  
Giuseppe Ortu ◽  
Piet W. J. de Groot ◽  
Fabien Cottier ◽  
Céline Loussert ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Fungal Pathogens ◽  
High Sensitivity ◽  
Wall Structure ◽  
Minor Role ◽  
Cell Wall Proteins ◽  
Calcofluor White ◽  
Fungal Cell ◽  
A Minor

The fungal cell wall is essential in maintaining cellular integrity and plays key roles in the interplay between fungal pathogens and their hosts. The PGA59 and PGA62 genes encode two short and related glycosylphosphatidylinositol-anchored cell wall proteins and their expression has been previously shown to be strongly upregulated when the human pathogen Candida albicans grows as biofilms. Using GFP fusion proteins, we have shown that Pga59 and Pga62 are cell-wall-located, N- and O-glycosylated proteins. The characterization of C. albicans pga59Δ/pga59Δ, pga62Δ/pga62Δ and pga59Δ/pga59Δ pga62Δ/pga62Δ mutants suggested a minor role of these two proteins in hyphal morphogenesis and that they are not critical to biofilm formation. Importantly, the sensitivity to different cell-wall-perturbing agents was altered in these mutants. In particular, simultaneous inactivation of PGA59 and PGA62 resulted in high sensitivity to Calcofluor white, Congo red and nikkomicin Z and in resistance to caspofungin. Furthermore, cell wall composition and observation by transmission electron microscopy indicated an altered cell wall structure in the mutant strains. Collectively, these data suggest that the cell wall proteins Pga59 and Pga62 contribute to cell wall stability and structure.

scholarly journals Chromatin remodeling by the SWI/SNF complex is essential for transcription mediated by the yeast cell wall integrity MAPK pathway

2012 ◽  
Vol 23 (14) ◽  
pp. 2805-2817 ◽  
Author(s):  
A. Belén Sanz ◽  
Raúl García ◽  
Jose Manuel Rodríguez-Peña ◽  
Sonia Díez-Muñiz ◽  
César Nombela ◽  
...  
Keyword(s):  
Cell Wall ◽  
Chromatin Remodeling ◽  
Mapk Pathway ◽  
Critical Role ◽  
Transcriptional Response ◽  
Wall Stress ◽  
Cell Wall Integrity ◽  
Mitogen Activated Protein Kinase ◽  
Cell Wall Stress ◽  
Mitogen Activated Protein

In Saccharomyces cerevisiae, the transcriptional program triggered by cell wall stress is coordinated by Slt2/Mpk1, the mitogen-activated protein kinase (MAPK) of the cell wall integrity (CWI) pathway, and is mostly mediated by the transcription factor Rlm1. Here we show that the SWI/SNF chromatin-remodeling complex plays a critical role in orchestrating the transcriptional response regulated by Rlm1. swi/snf mutants show drastically reduced expression of cell wall stress–responsive genes and hypersensitivity to cell wall–interfering compounds. On stress, binding of RNA Pol II to the promoters of these genes depends on Rlm1, Slt2, and SWI/SNF. Rlm1 physically interacts with SWI/SNF to direct its association to target promoters. Finally, we observe nucleosome displacement at the CWI-responsive gene MLP1/KDX1, which relies on the SWI/SNF complex. Taken together, our results identify the SWI/SNF complex as a key element of the CWI MAPK pathway that mediates the chromatin remodeling necessary for adequate transcriptional response to cell wall stress.

scholarly journals Clotrimazole-Induced Oxidative Stress Triggers Novel Yeast Pkc1-Independent Cell Wall Integrity MAPK Pathway Circuitry

2021 ◽  
Vol 7 (8) ◽  
pp. 647
Author(s):  
Ángela Sellers-Moya ◽  
Marcos Nuévalos ◽  
María Molina ◽  
Humberto Martín
Keyword(s):  
Oxidative Stress ◽  
Cell Wall ◽  
Stress Responses ◽  
Fungal Infections ◽  
Mapk Pathway ◽  
Mapk Signaling ◽  
Cell Wall Integrity ◽  
Strong Impact ◽  
Yeast Saccharomyces Cerevisiae ◽  
Activation Motif

Azoles are one of the most widely used drugs to treat fungal infections. To further understand the fungal response to azoles, we analyzed the MAPK circuitry of the model yeast Saccharomyces cerevisiae that operates under treatment with these antifungals. Imidazoles, and particularly clotrimazole, trigger deeper changes in MAPK phosphorylation than triazoles, involving a reduction in signaling through the mating pathway and the activation of the MAPKs Hog1 and Slt2 from the High-Osmolarity Glycerol (HOG) and the Cell Wall Integrity (CWI) pathways, respectively. Clotrimazole treatment leads to actin aggregation, mitochondrial alteration, and oxidative stress, which is essential not only for the activation of both MAPKs, but also for the appearance of a low-mobility form of Slt2 caused by additional phosphorylation to that occurring at the conserved TEY activation motif. Clotrimazole-induced ROS production and Slt2 phosphorylation are linked to Tpk3-mediated PKA activity. Resistance to clotrimazole depends on HOG and CWI-pathway-mediated stress responses. However, Pkc1 and other proteins acting upstream in the pathway are not critical for the activation of the Slt2 MAPK module, suggesting a novel rewiring of signaling through the CWI pathway. We further show that the strong impact of azole treatment on MAPK signaling is conserved in other yeast species.

scholarly journals Arabidopsis Mutants Lacking Long Chain Base Phosphate Lyase Are Fumonisin-sensitive and Accumulate Trihydroxy-18:1 Long Chain Base Phosphate

2007 ◽  
Vol 282 (38) ◽  
pp. 28195-28206 ◽  
Author(s):  
Yoseph Tsegaye ◽  
Christopher G. Richardson ◽  
Janis E. Bravo ◽  
Brendan J. Mulcahy ◽  
Daniel V. Lynch ◽  
...  
Keyword(s):  
Sphingolipid Metabolism ◽  
Minor Role ◽  
Ceramide Synthase ◽  
Developmental Abnormalities ◽  
Chain Base ◽  
Long Chain Base ◽  
Lyase Activity ◽  
A Minor ◽  
Eukaryotic Organisms ◽  
Long Chain

The sphingoid long chain bases (LCBs) and their phosphorylated derivatives (LCB-Ps) are important signaling molecules in eukaryotic organisms. The cellular levels of LCB-Ps are tightly controlled by the coordinated action of the LCB kinase activity responsible for their synthesis and the LCB-P phosphatase and lyase activities responsible for their catabolism. Although recent studies have implicated LCB-Ps as regulatory molecules in plants, in comparison with yeast and mammals, much less is known about their metabolism and function in plants. To investigate the functions of LCB-Ps in plants, we have undertaken the identification and characterization of Arabidopsis genes that encode the enzymes of LCB-P metabolism. In this study the Arabidopsis At1g27980 gene was shown to encode the only detectable LCB-P lyase activity in Arabidopsis. The LCB-P lyase activity was characterized, and mutant plant lines lacking the lyase were generated and analyzed. Whereas in other organisms loss of LCB-P lyase activity is associated with accumulation of high levels of LCB/LCB-Ps and developmental abnormalities, the sphingolipid profiles of the mutant plants were remarkably similar to those of wild-type plants, and no developmental abnormalities were observed. Thus, these studies indicate that the lyase plays a minor role in maintenance of sphingolipid metabolism during normal plant development and growth. However, a clear role for the lyase was revealed upon perturbation of sphingolipid synthesis by treatment with the inhibitor of ceramide synthase, fumonisin B1.

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