scholarly journals A Role for the Rap GTPase YlRsr1 in Cellular Morphogenesis and the Involvement of YlRsr1 and the Ras GTPase YlRas2 in Bud Site Selection in the Dimorphic Yeast Yarrowia lipolytica

2014 ◽  
Vol 13 (5) ◽  
pp. 580-590 ◽  
Author(s):  
Yun-Qing Li ◽  
Min Li ◽  
Xiao-Feng Zhao ◽  
Xiang-Dong Gao
Keyword(s):  
Yarrowia Lipolytica ◽  
Site Selection ◽  
Bound States ◽  
Selection Process ◽  
Content Type ◽  
Yeast Form ◽  
Ras Gtpase ◽  
Cellular Morphogenesis ◽  
Dimorphic Yeast ◽  
Bud Site

ABSTRACT Yarrowia lipolytica is a dimorphic yeast species that can grow in the ovoid yeast form or in the elongated pseudohyphal or hyphal form depending on the growth conditions. Here, we show that the Rap GTPase Rsr1 of Y. lipolytica (YlRsr1) plays an important role in cellular morphogenesis in this microorganism. Cells deleted for Yl RSR1 exhibited impaired polarized growth during yeast-form growth. Pseudohyphal and hyphal development were also abnormal. YlRsr1 is also important for cell growth, since the deletion of Yl RSR1 in cells lacking the Ras GTPase YlRas2 caused lethality. Y. lipolytica cells bud in a bipolar pattern in which the cells produce the new buds at the two poles. YlRsr1 plays a prominent role in this bud site selection process. YlRsr1's function in bud site selection absolutely requires the cycling of YlRsr1 between the GTP- and GDP-bound states but its function in cellular morphogenesis does not, suggesting that the two processes are differentially regulated. Interestingly, the Ras GTPase YlRas2 is also involved in the control of bud site selection, as Yl ras2 Δ cells were severely impaired in bipolar bud site selection. The GTP/GDP cycling and the plasma membrane localization of YlRas2 are important for YlRas2's function in bud site selection. However, they are not essential for this process, suggesting that the mechanism by which YlRas2 acts is different from that of YlRsr1. Our results suggest that YlRsr1 is regulated by the GTPase-activating protein (GAP) YlBud2 and partially by YlCdc25, the potential guanine nucleotide exchange factor (GEF) for YlRas2.

scholarly journals Temporal regulation of cell polarity via the interaction of the Ras GTPase Rsr1 and the scaffold protein Bem1

2019 ◽  
Vol 30 (20) ◽  
pp. 2543-2557 ◽  
Author(s):  
Kristi E. Miller ◽  
Wing-Cheong Lo ◽  
Ching-Shan Chou ◽  
Hay-Oak Park
Keyword(s):  
Bound States ◽  
Scaffold Protein ◽  
Cell Polarization ◽  
Temporal Regulation ◽  
Ras Gtpase ◽  
Polarized Secretion ◽  
Associated Proteins ◽  
Guanosine Triphosphatase ◽  
Bud Site

The Cdc42 guanosine triphosphatase (GTPase) plays a central role in polarity development in species ranging from yeast to humans. In budding yeast, a specific growth site is selected in the G1 phase. Rsr1, a Ras GTPase, interacts with Cdc42 and its associated proteins to promote polarized growth at the proper bud site. Yet how Rsr1 regulates cell polarization is not fully understood. Here, we show that Rsr1-GDP interacts with the scaffold protein Bem1 in early G1, likely hindering the role of Bem1 in Cdc42 polarization and polarized secretion. Consistent with these in vivo observations, mathematical modeling predicts that Bem1 is unable to promote Cdc42 polarization in early G1 in the presence of Rsr1-GDP. We find that a part of the Bem1 Phox homology domain, which overlaps with a region interacting with the exocyst component Exo70, is necessary for the association of Bem1 with Rsr1-GDP. Overexpression of the GDP-locked Rsr1 interferes with Bem1-dependent Exo70 polarization. We thus propose that Rsr1 functions in spatial and temporal regulation of polarity establishment by associating with distinct polarity factors in its GTP- and GDP-bound states.

scholarly journals The pH-Responsive Transcription Factors YlRim101 and Mhy1 Regulate Alkaline pH-Induced Filamentation in the Dimorphic Yeast Yarrowia lipolytica

mSphere ◽  
2021 ◽  
Vol 6 (3) ◽  
Author(s):  
Tao Shu ◽  
Xin-Yu He ◽  
Jia-Wen Chen ◽  
Yi-Sheng Mao ◽  
Xiang-Dong Gao
Keyword(s):  
Cell Wall ◽  
Transcription Factor ◽  
Yarrowia Lipolytica ◽  
Regulatory Mechanism ◽  
Cell Wall Protein ◽  
Alkaline Ph ◽  
Dimorphic Fungi ◽  
Content Type ◽  
Dimorphic Yeast

ABSTRACT Environmental pH influences cell growth and differentiation. In the dimorphic yeast Yarrowia lipolytica, neutral-alkaline pH strongly induces the yeast-to-filament transition. However, the regulatory mechanism that governs alkaline pH-induced filamentation has been unclear. Here, we show that the pH-responsive transcription factor Y. lipolytica Rim101 (YlRim101) is a major regulator of alkaline-induced filamentation, since the deletion of YlRIM101 severely impaired filamentation at alkaline pH, whereas the constitutively active YlRIM1011-330 mutant mildly induced filamentation at acidic pH. YlRim101 controls the expression of the majority of alkaline-regulated cell wall protein genes. One of these, the cell surface glycosidase gene YlPHR1, plays a critical role in growth, cell wall function, and filamentation at alkaline pH. This finding suggests that YlRim101 promotes filamentation at alkaline pH via controlling the expression of these genes. We also show that, in addition to YlRim101, the Msn2/Msn4-like transcription factor Mhy1 is highly upregulated at alkaline pH and is essential for filamentation. However, unlike YlRim101, which specifically regulates alkaline-induced filamentation, Mhy1 regulates both alkaline- and glucose-induced filamentation, since the deletion of MHY1 abolished them both, whereas the overexpression of MHY1 induced strong filamentation irrespective of the pH or the presence of glucose. Finally, we show that YlRim101 and Mhy1 positively coregulate seven cell wall protein genes at alkaline pH, including YlPHR1 and five cell surface adhesin-like genes, three of which appear to promote filamentation. Together, these results reveal a conserved role of YlRim101 and a novel role of Mhy1 in the regulation of alkaline-induced filamentation in Y. lipolytica. IMPORTANCE The regulatory mechanism that governs pH-regulated filamentation is not clear in dimorphic fungi except in Candida albicans. Here, we investigated the regulation of alkaline pH-induced filamentation in Yarrowia lipolytica, a dimorphic yeast distantly related to C. albicans. Our results show that the transcription factor YlRim101 and the Msn2/Msn4-like transcription factor Mhy1 are the major regulators that promote filamentation at alkaline pH. They control the expression of a number of cell wall protein genes important for cell wall organization and filamentation. Our results suggest that the Rim101/PacC homologs play a conserved role in pH-regulated filamentation in dimorphic fungi.

scholarly journals The Anillin-Related Region of Bud4 Is the Major Functional Determinant for Bud4's Function in Septin Organization during Bud Growth and Axial Bud Site Selection in Budding Yeast

2015 ◽  
Vol 14 (3) ◽  
pp. 241-251 ◽  
Author(s):  
Huan Wu ◽  
Jia Guo ◽  
Ya-Ting Zhou ◽  
Xiang-Dong Gao
Keyword(s):  
Central Region ◽  
Site Selection ◽  
Related Protein ◽  
Functional Determinant ◽  
Content Type ◽  
C Terminus ◽  
Bud Neck ◽  
M Phase ◽  
Bud Growth ◽  
Bud Site

ABSTRACT The anillin-related protein Bud4 of Saccharomyces cerevisiae is required for axial bud site selection by linking the axial landmark to the septins, which localize at the mother bud neck. Recent studies indicate that Bud4 plays a role in septin organization during cytokinesis. Here we show that Bud4 is also involved in septin organization during bud growth prior to cytokinesis, as bud4 Δ shs1 Δ cells displayed an elongated bud morphology and defective septin organization at 18°C. Bud4 overexpression also affected septin organization during bud growth in shs1 Δ cells at 30°C. Bud4 was previously thought to associate with the septins via its central region, while the C-terminal anillin-related region was not involved in septin association. Surprisingly, we found that the central region of Bud4 alone targets to the bud neck throughout the cell cycle, unlike full-length Bud4, which localizes to the bud neck only during G 2 /M phase. We identified the anillin-related region to be a second targeting domain that cooperates with the central region for proper septin association. In addition, the anillin-related region could largely mediate Bud4's function in septin organization during bud growth and bud site selection. We show that this region interacts with the C terminus of Bud3 and the two segments depend on each other for association with the septins. Moreover, like the bud4 Δ mutant, the bud3 Δ mutant genetically interacts with shs1 Δ and cdc12-6 mutants in septin organization, suggesting that Bud4 and Bud3 may cooperate in septin organization during bud growth. These observations provide new insights into the interaction of Bud4 with the septins and Bud3.

scholarly journals Temporal regulation of cell polarity via the interaction of the Ras GTPase Rsr1 and the scaffold protein Bem1

2019 ◽  
Author(s):  
Kristi E. Miller ◽  
Hay-Oak Park
Keyword(s):  
Cell Polarity ◽  
Bound States ◽  
Bound State ◽  
Scaffold Protein ◽  
Cell Polarization ◽  
Temporal Regulation ◽  
Ras Gtpase ◽  
Px Domain ◽  
Associated Proteins ◽  
Bud Site

AbstractEstablishing cell polarity is critical for growth and development of most organisms. The Cdc42 GTPase plays a central role in polarity development in species ranging from yeast to humans. In budding yeast, a specific growth site (i.e. bud site) is selected in the G1 phase, which determines the axis of cell polarization. Rsr1, a Ras GTPase, interacts with Cdc42 and its associated proteins to promote polarized growth at the proper bud site. Yet the mechanism underlying spatial cue-directed cell polarization is not fully understood. Here, we show that Rsr1 associates with Bem1, a scaffold protein, preferentially in its GDP-bound state in early G1. This interaction involves a part of the Bem1 Phox homology (PX) domain, which overlaps with a region previously shown to interact with Exo70, an exocyst component. Furthermore, overexpression of the constitutively GDP-bound Rsr1 interferes with Bem1’s association with Exo70 and inhibits Bem1-dependent Exo70 polarization. We propose that Rsr1 plays a delicate role in coordination of spatial and temporal regulation of polarity establishment via its GTP- and GDP-bound states.

scholarly journals Experience of establishing and coordinating a nationwide network for bidirectional intussusception surveillance in India: lessons for multisite research studies

BMJ Open ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. e046827
Author(s):  
Manoja Kumar Das
Keyword(s):  
Quality Assurance ◽  
Site Selection ◽  
Information Seeking ◽  
Selection Process ◽  
Tertiary Care ◽  
Vaccine Safety ◽  
Secondary Outcome ◽  
Prospective Surveillance ◽  
Surveillance Network ◽  
Nationally Representative

ObjectivesTo document and share the process of establishing the nationally representative multisite surveillance network for intussusception in India, coordination, data management and lessons learnt from the implementation.DesignThis study combined both retrospective and prospective surveillance approaches.Setting19 tertiary care institutions were selected in India considering the geographic representation and public and private mixParticipantsAll children under-2 years of age with intussusceptionPrimary and secondary outcome measuresThe experience of site selection, regulatory approvals, data collection, quality assurance and network coordination were documented.ResultsThe site selection process involved systematic and objective four steps including shortlisting of potential institutions, information seeking and telephonic interaction, site visits and site selection using objective criteria. Out of over 400 hospitals screened across India, 40 potential institutions were shortlisted and information was sought by questionnaire and interaction with investigators. Out of these, 25 institutes were visited and 19 sites were finally selected to participate in the study. The multistep selection process allowed filtering and identification of sites with adequate capacity and motivated investigators. The retrospective surveillance documented 1588 cases (range: 14–652 cases/site) and prospective surveillance recruited 621 cases (range: 5–191 cases/site). The multilayer quality assurance measures monitored and ensured protocol adherence, complete record retrieval and data completeness. The key challenges experienced included time taken for obtaining regulatory and ethical approvals, which delayed completion of the study. Ten sites continued with another multisite vaccine safety surveillance study.ConclusionThe experience and results of this systematic and objective site selection method in India are promising. The systematic multistep site selection and data quality assurance methods presented here are feasible and practical. The lessons from the establishment and coordination of this surveillance network can be useful in planning, selecting the sites and conducting multisite and surveillance studies in India and developing countries.

scholarly journals SEC3 Mutations Are Synthetically Lethal With Profilin Mutations and Cause Defects in Diploid-Specific Bud-Site Selection

Genetics ◽  
1996 ◽  
Vol 144 (2) ◽  
pp. 495-510 ◽  
Author(s):  
B K Haarer ◽  
A Corbett ◽  
Y Kweon ◽  
A S Petzold ◽  
P Silver ◽  
...  
Keyword(s):  
Site Selection ◽  
Secretory Pathway ◽  
Wild Type ◽  
Synthetic Lethal ◽  
Abnormal Growth ◽  
Colony Color ◽  
Synthetically Lethal ◽  
Homozygous Diploid ◽  
Bud Site ◽  
Wild Type Yeast

Abstract Replacement of the wild-type yeast profilin gene (PFY1) with a mutated form (pfy1-111) that has codon 72 changed to encode glutamate rather than arginine results in defects similar to, but less severe than, those that result from complete deletion of the profilin gene. We have used a colony color-sectoring assay to identify mutations that cause pfy1-111, but not wild-type, cells to be inviable. These profilin synthetic lethal (psl) mutations result in various degrees of abnormal growth, morphology, and temperature sensitivity in PFY1 cells. We have examined psl1 strains in the most detail. Interestingly, these strains display a diploid-specific defect in bud-site selection; haploid strains bud normally, while homozygous diploid strains show a dramatic increase in random budding. We discovered that PSL1 is the late secretory gene, SEC3, and have found that mutations in several other late secretory genes are also synthetically lethal with pfy1-111. Our results are likely to reflect an interdependence between the actin cytoskeleton and secretory processes in directing cell polarity and growth. Moreover, they indicate that the secretory pathway is especially crucial for maintaining budding polarity in diploids.

Perceived value of internship experience: a try before you leap

2018 ◽  
Vol 8 (4) ◽  
pp. 376-394 ◽  
Author(s):  
Sonali Bhattacharya ◽  
Netra Neelam
Keyword(s):  
Experiential Learning ◽  
Performance Feedback ◽  
Work Experience ◽  
Selection Process ◽  
Learning Orientation ◽  
Research Approach ◽  
Content Type ◽  
Internship Experience ◽  
And Performance ◽  
Task Variety

Purpose The purpose of this paper is to examine how internship value is manifested in the context of a business school. The authors have examined the internship experience in terms of experiential learning and employability. Specifically, the authors investigate the factors that determine internship at four phases: design, conduct, evaluation and feedback. Design/methodology/approach The authors have applied a mixed method approach. In all, 110 students of a busines school were first surveyed on their expectation, motivation and level of preparation through a self-administered questionnaire before internship. Based on the survey result, eight of these students were interviewed in details about internship expectations from industry, the selection process for internship, communications or exchanges between intern and companies prior to internship and perceived industry expectation from interns. At the next phase, authors used a qualitative research approach by conducting semi-structured, in-depth interviews with 14 interns and their mentors after internship period. They were interviewed on design, conduct, evaluation and feedback process of the internship. Interviews tried capture what kind of leader-member exchange led to satisfactory internship experience and outcome from view of both inter and mentor. Findings The authors find that at various stages of internship program quality of mentor – intern exchanges (as defined by leadership exchange theory), and task characteristics as indicated by autonomy, task variety, task significance and performance feedback determine intern’s performance. An intern’s performance is antecedent to an intern’s and a mentor’s satisfaction and overall internship value. The authors also found that intrinsic capability of intern such as critical thinking ability and learning orientation result in enhanced value of internship experience. The proposed models, postulate that at designing stage, lower the level of communication from employers, higher the feeling of ambiguity and lower the perceived internship value in terms of experiential learning and perceived employability. Feeling of ambiguity is moderated by existence of prior work experience of interns. At conduction stage, mentor-intern exchange is directly related to flexibility in structure of the program and inversely related to dependency on peer learning. Mentor-intern exchange also related to mentor and intern’s learning value. However, the learning value is moderated by learning orientation of the intern. Originality/value The authors have tried the summer internship experience from the perspective of interns and mentors. This is the uniqueness of the research.

scholarly journals A Role for the Actin Cytoskeleton of Saccharomyces cerevisiae in Bipolar Bud-Site Selection

1997 ◽  
Vol 136 (1) ◽  
pp. 111-123 ◽  
Author(s):  
Shirley Yang ◽  
Kathryn R. Ayscough ◽  
David G. Drubin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Actin Cytoskeleton ◽  
Site Selection ◽  
Mitotic Checkpoint ◽  
Cell Cortex ◽  
Spatial Cues ◽  
Genes Encoding ◽  
Mother And Daughter ◽  
Mother Cells ◽  
Bud Site

Saccharomyces cerevisiae cells select bud sites according to one of two predetermined patterns. MATa and MATα cells bud in an axial pattern, and MATa/α cells bud in a bipolar pattern. These budding patterns are thought to depend on the placement of spatial cues at specific sites in the cell cortex. Because cytoskeletal elements play a role in organizing the cytoplasm and establishing distinct plasma membrane domains, they are well suited for positioning bud-site selection cues. Indeed, the septin-containing neck filaments are crucial for establishing the axial budding pattern characteristic of MATa and MATα cells. In this study, we determined the budding patterns of cells carrying mutations in the actin gene or in genes encoding actin-associated proteins: MATa/α cells were defective in the bipolar budding pattern, but MATa and MATα cells still exhibit a normal axial budding pattern. We also observed that MATa/α actin cytoskeleton mutant daughter cells correctly position their first bud at the distal pole of the cell, but mother cells position their buds randomly. The actin cytoskeleton therefore functions in generation of the bipolar budding pattern and is required specifically for proper selection of bud sites in mother MATa/α cells. These observations and the results of double mutant studies support the conclusion that different rules govern bud-site selection in mother and daughter MATa/α cells. A defective bipolar budding pattern did not preclude an sla2-6 mutant from undergoing pseudohyphal growth, highlighting the central role of daughter cell bud-site selection cues in the formation of pseudohyphae. Finally, by examining the budding patterns of mad2-1 mitotic checkpoint mutants treated with benomyl to depolymerize their microtubules, we confirmed and extended previous evidence indicating that microtubules do not function in axial or bipolar bud-site selection.

scholarly journals Snf1 Is a Regulator of Lipid Accumulation in Yarrowia lipolytica

2013 ◽  
Vol 79 (23) ◽  
pp. 7360-7370 ◽  
Author(s):  
John Seip ◽  
Raymond Jackson ◽  
Hongxian He ◽  
Quinn Zhu ◽  
Seung-Pyo Hong
Keyword(s):  
Yarrowia Lipolytica ◽  
Lipid Accumulation ◽  
Oleaginous Yeast ◽  
De Novo ◽  
Lipid Synthesis ◽  
Omega 3 ◽  
Wild Type ◽  
Content Type ◽  
Reverse Transcription Pcr ◽  
Dry Cell Weight

ABSTRACTIn the oleaginous yeastYarrowia lipolytica,de novolipid synthesis and accumulation are induced under conditions of nitrogen limitation (or a high carbon-to-nitrogen ratio). The regulatory pathway responsible for this induction has not been identified. Here we report that the SNF1 pathway plays a key role in the transition from the growth phase to the oleaginous phase inY. lipolytica. Strains with aY. lipolyticasnf1(Ylsnf1) deletion accumulated fatty acids constitutively at levels up to 2.6-fold higher than those of the wild type. When introduced into aY. lipolyticastrain engineered to produce omega-3 eicosapentaenoic acid (EPA),Ylsnf1deletion led to a 52% increase in EPA titers (7.6% of dry cell weight) over the control. Other components of theY. lipolyticaSNF1 pathway were also identified, and their function in limiting fatty acid accumulation is suggested by gene deletion analyses. Deletion of the gene encoding YlSnf4, YlGal83, or YlSak1 significantly increased lipid accumulation in both growth and oleaginous phases compared to the wild type. Furthermore, microarray and quantitative reverse transcription-PCR (qRT-PCR) analyses of theYlsnf1mutant identified significantly differentially expressed genes duringde novolipid synthesis and accumulation inY. lipolytica. Gene ontology analysis found that these genes were highly enriched with genes involved in lipid metabolism. This work presents a new role for Snf1/AMP-activated protein kinase (AMPK) pathways in lipid accumulation in this oleaginous yeast.

Adaptive neuro-fuzzy fusion of multi-sensor data for monitoring of CNC machining

Sensor Review ◽  
2017 ◽  
Vol 37 (1) ◽  
pp. 78-81 ◽  
Author(s):  
Srdjan Jovic ◽  
Obrad Anicic ◽  
Milivoje Jovanovic
Keyword(s):  
Selection Process ◽  
Spindle Speed ◽  
Cnc Machining ◽  
Numerical Control ◽  
Periodic Component ◽  
Sensor Data ◽  
Depth Of Cut ◽  
Inference System ◽  
Content Type ◽  
Neuro Fuzzy

Purpose Acoustic emission (AE) could be used for prevention and detection of tool errors in Computer Numerical Control (CNC) machining. The purpose of this study is to analyze the AE form of CNC machining operations. Design/methodology/approach Experimental measurements were performed with three sensors on the CNC lathe to collect the data of the CNC machining. Adaptive neuro-fuzzy inference system (ANFIS) was applied for the fusion from the sensors’ signals to determine the strength of the signal periodic component among the sensors. Findings There were three inputs, namely, spindle speed, feed rate and depth of cut. ANFIS was also used to determine the inputs’ influence on the prediction of strength of the signal periodic component. Variable selection process was used to select the most dominant factors which affect the prediction of strength of the signal periodic component. Originality/value Results were shown that the spindle speed has the most dominant effect on the strength of the signal periodic component.

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