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Li K, Zhai L, Pi Y, Fu S, Wu T, Zhang X, Xu X, Han Z, Wang Y. Mitogen-activated protein kinase MxMPK3-2 mediated phosphorylation of MxZR3.1 participates in regulating iron homoeostasis in apple rootstocks. PLANT, CELL & ENVIRONMENT 2024; 47:2510-2525. [PMID: 38514902 DOI: 10.1111/pce.14897] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 01/29/2024] [Accepted: 03/11/2024] [Indexed: 03/23/2024]
Abstract
The micronutrient iron plays a crucial role in the growth and development of plants, necessitating meticulous regulation for its absorption by plants. Prior research has demonstrated that the transcription factor MxZR3.1 restricts iron absorption in apple rootstocks; however, the precise mechanism by which MxZR3.1 contributes to the regulation of iron homoeostasis in apple rootstocks remains unexplored. Here, MxMPK3-2, a protein kinase, was discovered to interact with MxZR3.1. Y2H, bimolecular fluorescence complementation and pull down experiments were used to confirm the interaction. Phosphorylation and cell semi-degradation tests have shown that MxZR3.1 can be used as a substrate of MxMPK3-2, which leads to the MxZR3.1 protein being more stable. In addition, through tobacco transient transformation (LUC and GUS) experiments, it was confirmed that MxZR3.1 significantly inhibited the activity of the MxHA2 promoter, while MxMPK3-2 mediated phosphorylation at the Ser94 site of MxZR3.1 further inhibited the activity of the MxHA2 promoter. It is tightly controlled to absorb iron during normal growth and development of apple rootstocks due to the regulatory effect of the MxMPK3-2-MxZR3.1 module on MxHA2 transcription level. Consequently, this research has revealed the molecular basis of how the MxMPK3-2-MxZR3.1 module in apple rootstocks controls iron homoeostasis by regulating the MxHA2 promoter's activity.
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Affiliation(s)
- Keting Li
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
| | - Longmei Zhai
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
| | - Ying Pi
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
| | - Sitong Fu
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
| | - Ting Wu
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
| | - Xinzhong Zhang
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
| | - Xuefeng Xu
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
| | - Zhenhai Han
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
| | - Yi Wang
- College of Horticulture, China Agricultural University, Beijing, China
- Key Laboratory of Biology and Genetic Improvement of Horticultural Crops (Nutrition and Physiology), Ministry of Agriculture and Rural Affairs of the People's Republic of China, Beijing, China
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Pajić T, Stevanović K, Todorović NV, Krmpot AJ, Živić M, Savić-Šević S, Lević SM, Stanić M, Pantelić D, Jelenković B, Rabasović MD. In vivo femtosecond laser nanosurgery of the cell wall enabling patch-clamp measurements on filamentous fungi. MICROSYSTEMS & NANOENGINEERING 2024; 10:47. [PMID: 38590818 PMCID: PMC10999429 DOI: 10.1038/s41378-024-00664-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/20/2023] [Revised: 12/01/2023] [Accepted: 12/19/2023] [Indexed: 04/10/2024]
Abstract
Studying the membrane physiology of filamentous fungi is key to understanding their interactions with the environment and crucial for developing new therapeutic strategies for disease-causing pathogens. However, their plasma membrane has been inaccessible for a micron-sized patch-clamp pipette for pA current recordings due to the rigid chitinous cell wall. Here, we report the first femtosecond IR laser nanosurgery of the cell wall of the filamentous fungi, which enabled patch-clamp measurements on protoplasts released from hyphae. A reproducible and highly precise (diffraction-limited, submicron resolution) method for obtaining viable released protoplasts was developed. Protoplast release from the nanosurgery-generated incisions in the cell wall was achieved from different regions of the hyphae. The plasma membrane of the obtained protoplasts formed tight and high-resistance (GΩ) contacts with the recording pipette. The entire nanosurgical procedure followed by the patch-clamp technique could be completed in less than 1 hour. Compared to previous studies using heterologously expressed channels, this technique provides the opportunity to identify new ionic currents and to study the properties of the ion channels in the protoplasts of filamentous fungi in their native environment.
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Grants
- Ministarstvo Prosvete, Nauke i Tehnološkog Razvoja (Ministry of Education, Science and Technological Development of the Republic of Serbia)
- This work was supported by the Ministry of Science, Technological Development and Innovations, Republic of Serbia [contract number: 451-03-47/2023-01/200178]; The Project Advanced Biophysical Methods for Soil Targeted Fungi-Based Biocontrol Agents - BioPhysFUN [Grant number 4545] from Program DEVELOPMENT – Green program of cooperation between science and industry, Science Fund of the Republic of Serbia
- This work was supported by the Ministry of Science, Technological Development and Innovations, Republic of Serbia [contract number: 451-03-47/2023-01/200007]; The Project Advanced Biophysical Methods for Soil Targeted Fungi-Based Biocontrol Agents - BioPhysFUN [Grant number 4545] from Program DEVELOPMENT – Green program of cooperation between science and industry, Science Fund of the Republic of Serbia
- The Project Advanced Biophysical Methods for Soil Targeted Fungi-Based Biocontrol Agents - BioPhysFUN [Grant number 4545] from Program DEVELOPMENT – Green program of cooperation between science and industry, Science Fund of the Republic of Serbia; the Project HEMMAGINERO [Grant number 6066079] from Program PROMIS, Science Fund of the Republic of Serbia; and the Institute of Physics Belgrade, through the grant by the Ministry of Science, Technological Development and Innovations of the Republic of Serbia.
- The Institute of Physics Belgrade, through the grant by the Ministry of Science, Technological Development and Innovations of the Republic of Serbia
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Affiliation(s)
- Tanja Pajić
- Institute of Physiology and Biochemistry “Ivan Djaja”, Faculty of Biology, University of Belgrade, Studentski trg 16, 11158 Belgrade, Serbia
| | - Katarina Stevanović
- Institute of Physiology and Biochemistry “Ivan Djaja”, Faculty of Biology, University of Belgrade, Studentski trg 16, 11158 Belgrade, Serbia
| | - Nataša V. Todorović
- Institute for Biological Research “Siniša Stanković”, University of Belgrade, National Institute of the Republic of Serbia, Bulevar Despota Stefana 142, 11000 Belgrade, Serbia
| | - Aleksandar J. Krmpot
- Institute of Physics Belgrade, University of Belgrade, National Institute of the Republic of Serbia, Pregrevica 118, 11080 Belgrade, Serbia
| | - Miroslav Živić
- Institute of Physiology and Biochemistry “Ivan Djaja”, Faculty of Biology, University of Belgrade, Studentski trg 16, 11158 Belgrade, Serbia
| | - Svetlana Savić-Šević
- Institute of Physics Belgrade, University of Belgrade, National Institute of the Republic of Serbia, Pregrevica 118, 11080 Belgrade, Serbia
| | - Steva M. Lević
- University of Belgrade, Faculty of Agriculture, Nemanjina Street 6, 11080 Belgrade, Serbia
| | - Marina Stanić
- Institute for Multidisciplinary Research, University of Belgrade, Kneza Višeslava 1, 11030 Belgrade, Serbia
| | - Dejan Pantelić
- Institute of Physics Belgrade, University of Belgrade, National Institute of the Republic of Serbia, Pregrevica 118, 11080 Belgrade, Serbia
| | - Brana Jelenković
- Institute of Physics Belgrade, University of Belgrade, National Institute of the Republic of Serbia, Pregrevica 118, 11080 Belgrade, Serbia
| | - Mihailo D. Rabasović
- Institute of Physics Belgrade, University of Belgrade, National Institute of the Republic of Serbia, Pregrevica 118, 11080 Belgrade, Serbia
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3
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Cai F, Zhao Z, Gao R, Chen P, Ding M, Jiang S, Fu Z, Xu P, Chenthamara K, Shen Q, Bayram Akcapinar G, Druzhinina IS. The pleiotropic functions of intracellular hydrophobins in aerial hyphae and fungal spores. PLoS Genet 2021; 17:e1009924. [PMID: 34788288 PMCID: PMC8635391 DOI: 10.1371/journal.pgen.1009924] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Revised: 12/01/2021] [Accepted: 11/03/2021] [Indexed: 11/19/2022] Open
Abstract
Higher fungi can rapidly produce large numbers of spores suitable for aerial dispersal. The efficiency of the dispersal and spore resilience to abiotic stresses correlate with their hydrophobicity provided by the unique amphiphilic and superior surface-active proteins-hydrophobins (HFBs)-that self-assemble at hydrophobic/hydrophilic interfaces and thus modulate surface properties. Using the HFB-enriched mold Trichoderma (Hypocreales, Ascomycota) and the HFB-free yeast Pichia pastoris (Saccharomycetales, Ascomycota), we revealed that the rapid release of HFBs by aerial hyphae shortly prior to conidiation is associated with their intracellular accumulation in vacuoles and/or lipid-enriched organelles. The occasional internalization of the latter organelles in vacuoles can provide the hydrophobic/hydrophilic interface for the assembly of HFB layers and thus result in the formation of HFB-enriched vesicles and vacuolar multicisternal structures (VMSs) putatively lined up by HFBs. These HFB-enriched vesicles and VMSs can become fused in large tonoplast-like organelles or move to the periplasm for secretion. The tonoplast-like structures can contribute to the maintenance of turgor pressure in aerial hyphae supporting the erection of sporogenic structures (e.g., conidiophores) and provide intracellular force to squeeze out HFB-enriched vesicles and VMSs from the periplasm through the cell wall. We also show that the secretion of HFBs occurs prior to the conidiation and reveal that the even spore coating of HFBs deposited in the extracellular matrix requires microscopic water droplets that can be either guttated by the hyphae or obtained from the environment. Furthermore, we demonstrate that at least one HFB, HFB4 in T. guizhouense, is produced and secreted by wetted spores. We show that this protein possibly controls spore dormancy and contributes to the water sensing mechanism required for the detection of germination conditions. Thus, intracellular HFBs have a range of pleiotropic functions in aerial hyphae and spores and are essential for fungal development and fitness.
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Affiliation(s)
- Feng Cai
- The Key Laboratory of Plant Immunity, Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing, China
- Fungal Genomics Laboratory (FungiG), Nanjing Agricultural University, Nanjing, China
- Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), TU Wien, Vienna, Austria
| | - Zheng Zhao
- Fungal Genomics Laboratory (FungiG), Nanjing Agricultural University, Nanjing, China
| | - Renwei Gao
- Fungal Genomics Laboratory (FungiG), Nanjing Agricultural University, Nanjing, China
| | - Peijie Chen
- Fungal Genomics Laboratory (FungiG), Nanjing Agricultural University, Nanjing, China
| | - Mingyue Ding
- Fungal Genomics Laboratory (FungiG), Nanjing Agricultural University, Nanjing, China
| | - Siqi Jiang
- Fungal Genomics Laboratory (FungiG), Nanjing Agricultural University, Nanjing, China
| | - Zhifei Fu
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Science, Beijing, China
| | - Pingyong Xu
- Key Laboratory of RNA Biology, Institute of Biophysics, Chinese Academy of Science, Beijing, China
| | - Komal Chenthamara
- Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), TU Wien, Vienna, Austria
| | - Qirong Shen
- The Key Laboratory of Plant Immunity, Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing, China
- * E-mail: (QS); (ISD)
| | - Günseli Bayram Akcapinar
- Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), TU Wien, Vienna, Austria
- Department of Medical Biotechnology, Institute of Health Sciences, Acibadem Mehmet Ali Aydinlar University, Istanbul, Turkey
| | - Irina S. Druzhinina
- The Key Laboratory of Plant Immunity, Jiangsu Provincial Key Lab of Solid Organic Waste Utilization, Nanjing Agricultural University, Nanjing, China
- Fungal Genomics Laboratory (FungiG), Nanjing Agricultural University, Nanjing, China
- Institute of Chemical, Environmental and Bioscience Engineering (ICEBE), TU Wien, Vienna, Austria
- * E-mail: (QS); (ISD)
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4
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Wu H, Wong JWC. Current challenges for shaping the sustainable and mold-free hygienic indoor environment in humid regions. Lett Appl Microbiol 2020; 70:396-406. [PMID: 32180231 DOI: 10.1111/lam.13291] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 03/13/2020] [Accepted: 03/13/2020] [Indexed: 11/26/2022]
Abstract
Indoor mold grows ubiquitously in humid areas and can affect occupants' health. To prevent indoor mold contamination, one of the key measures suggested by the World Health Organisation and United States Environmental Protection Agency is to maintain an indoor relative humidity (RH) level below 75% or at 30-60%, respectively. However, in tropical and subtropical areas, maintaining these suggested RH levels is equivalent to operating a 24-h air-conditioner (AC) or dehumidifier, which is energy-consuming. As a large part of building expense, the operation time of ACs has been regularly proposed to be cut down because of the requirement of building sustainability. This leads to a trade-off between sustainable building performance and indoor mold hygiene. To balance this trade-off, more sustainable alternatives, such as those that target physical environments (e.g. nutrient and temperature level) or apply new surface coating technologies to inhibit mold growth, have been launched. Despite these initiatives, indoor mold contamination remains an unresolved issue, mainly because these alternative measures only exhibit limited effectiveness or require extra effort. This review aims to summarize the currently adopted mold control measures and discuss their limitations as well as the direction for the future development of sustainable mold control strategies. SIGNIFICANCE AND IMPACT OF THE STUDY: People spend most of their time indoors and hence the presence of indoor mold contamination can compromise the occupants' health. With the wake of climate change which is expected to see an increase in RH and temperature, tropical and subtropical areas are even more prone to mold contamination than they used to be. This study may help facilitate the development of sustainable and effective mold control strategies in the indoor environment.
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Affiliation(s)
- H Wu
- Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region, China.,Institute of Bioresource and Agriculture, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region, China
| | - J W C Wong
- Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region, China.,Institute of Bioresource and Agriculture, Hong Kong Baptist University, Kowloon Tong, Hong Kong Special Administrative Region, China
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5
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Foster AJ, Ryder LS, Kershaw MJ, Talbot NJ. The role of glycerol in the pathogenic lifestyle of the rice blast fungus Magnaporthe oryzae. Environ Microbiol 2017; 19:1008-1016. [PMID: 28165657 DOI: 10.1111/1462-2920.13688] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The rice blast fungus Magnaporthe oryzae elaborates a specialized cell called an appressorium, which is used to breach the tough outer cuticle of a rice leaf, enabling the fungus entry to host plant cells. The appressorium generates enormous turgor by accumulating glycerol to very high concentrations within the cell. Glycerol accumulation and melanization of the appressorium cell wall collectively drive turgor-mediated penetration of the rice leaf. In this review, we discuss the potential metabolic sources of glycerol in the rice blast fungus and how appressorium turgor is focused as physical force at the base of the infection cell, leading to the formation of a rigid penetration peg. We review recent studies of M. oryzae and other relevant appressorium-forming fungi which shed light on how glycerol is synthesized and how appressorium turgor is regulated. Finally, we provide some questions to guide avenues of future research that will be important in fully understanding the role of glycerol in rice blast disease.
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Affiliation(s)
- Andrew J Foster
- School of Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
| | - Lauren S Ryder
- School of Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
| | - Michael J Kershaw
- School of Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
| | - Nicholas J Talbot
- School of Biosciences, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK
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6
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Volkov V. Salinity tolerance in plants. Quantitative approach to ion transport starting from halophytes and stepping to genetic and protein engineering for manipulating ion fluxes. FRONTIERS IN PLANT SCIENCE 2015; 6:873. [PMID: 26579140 PMCID: PMC4621421 DOI: 10.3389/fpls.2015.00873] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 10/01/2015] [Indexed: 05/18/2023]
Abstract
Ion transport is the fundamental factor determining salinity tolerance in plants. The Review starts from differences in ion transport between salt tolerant halophytes and salt-sensitive plants with an emphasis on transport of potassium and sodium via plasma membranes. The comparison provides introductory information for increasing salinity tolerance. Effects of salt stress on ion transport properties of membranes show huge opportunities for manipulating ion fluxes. Further steps require knowledge about mechanisms of ion transport and individual genes of ion transport proteins. Initially, the Review describes methods to measure ion fluxes, the independent set of techniques ensures robust and reliable basement for quantitative approach. The Review briefly summarizes current data concerning Na(+) and K(+) concentrations in cells, refers to primary thermodynamics of ion transport and gives special attention to individual ion channels and transporters. Simplified scheme of a plant cell with known transport systems at the plasma membrane and tonoplast helps to imagine the complexity of ion transport and allows choosing specific transporters for modulating ion transport. The complexity is enhanced by the influence of cell size and cell wall on ion transport. Special attention is given to ion transporters and to potassium and sodium transport by HKT, HAK, NHX, and SOS1 proteins. Comparison between non-selective cation channels and ion transporters reveals potential importance of ion transporters and the balance between the two pathways of ion transport. Further on the Review describes in detail several successful attempts to overexpress or knockout ion transporters for changing salinity tolerance. Future perspectives are questioned with more attention given to promising candidate ion channels and transporters for altered expression. Potential direction of increasing salinity tolerance by modifying ion channels and transporters using single point mutations is discussed and questioned. An alternative approach from synthetic biology is to create new regulation networks using novel transport proteins with desired properties for transforming agricultural crops. The approach had not been widely used earlier; it leads also to theoretical and pure scientific aspects of protein chemistry, structure-function relations of membrane proteins, systems biology and physiology of stress and ion homeostasis. Summarizing, several potential ways are aimed at required increase in salinity tolerance of plants of interest.
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Affiliation(s)
- Vadim Volkov
- Faculty of Life Sciences and Computing, London Metropolitan UniversityLondon, UK
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7
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Muralidhar A, Shabala L, Broady P, Shabala S, Garrill A. Mechanisms underlying turgor regulation in the estuarine alga Vaucheria erythrospora (Xanthophyceae) exposed to hyperosmotic shock. PLANT, CELL & ENVIRONMENT 2015; 38:1514-1527. [PMID: 25546818 DOI: 10.1111/pce.12503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 12/07/2014] [Accepted: 12/11/2014] [Indexed: 06/04/2023]
Abstract
Aquatic organisms are often exposed to dramatic changes in salinity in the environment. Despite decades of research, many questions related to molecular and physiological mechanisms mediating sensing and adaptation to salinity stress remain unanswered. Here, responses of Vaucheria erythrospora, a turgor-regulating xanthophycean alga from an estuarine habitat, have been investigated. The role of ion uptake in turgor regulation was studied using a single cell pressure probe, microelectrode ion flux estimation (MIFE) technique and membrane potential (Em ) measurements. Turgor recovery was inhibited by Gd(3+) , tetraethylammonium chloride (TEA), verapamil and orthovanadate. A NaCl-induced shock rapidly depolarized the plasma membrane while an isotonic sorbitol treatment hyperpolarized it. Turgor recovery was critically dependent on the presence of Na(+) but not K(+) and Cl(-) in the incubation media. Na(+) uptake was strongly decreased by amiloride and changes in net Na(+) and H(+) fluxes were oppositely directed. This suggests active uptake of Na(+) in V. erythrospora mediated by an antiport Na(+) /H(+) system, functioning in the direction opposite to that of the SOS1 exchanger in higher plants. The alga also retains K(+) efficiently when exposed to high NaCl concentrations. Overall, this study provides insights into mechanisms enabling V. erythrospora to regulate turgor via ion movements during hyperosmotic stress.
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Affiliation(s)
- Abishek Muralidhar
- School of Biological Sciences, University of Canterbury, Christchurch, 8011, New Zealand
| | - Lana Shabala
- School of Land and Food and Tasmanian Institute for Agriculture, University of Tasmania, Hobart, Tasmania, 7001, Australia
| | - Paul Broady
- School of Biological Sciences, University of Canterbury, Christchurch, 8011, New Zealand
| | - Sergey Shabala
- School of Land and Food and Tasmanian Institute for Agriculture, University of Tasmania, Hobart, Tasmania, 7001, Australia
| | - Ashley Garrill
- School of Biological Sciences, University of Canterbury, Christchurch, 8011, New Zealand
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8
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Lew RR, Giblon RE, Lorenti MSH. The phenotype of a phospholipase C (plc-1) mutant in a filamentous fungus, Neurospora crassa. Fungal Genet Biol 2015. [PMID: 26212074 DOI: 10.1016/j.fgb.2015.07.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In the filamentous fungus Neurospora crassa, phospholipase C may play a role in hyphal extension at the growing tips as part of a growth-sensing mechanism that activates calcium release from internal stores to mediate continued expansion of the hyphal tip. One candidate for a tip-localized phospholipase C is PLC-1. We characterized morphology and growth characteristics of a knockout mutant (KO plc-1) and a RIP mutated strain (RIP plc-1) (missense mutations and a nonsense mutation render the gene product non-functional). Growth and hyphal cytology of wildtype and KO plc-1 were similar, but the RIP plc-1 mutant grew slower and exhibited abnormal membrane structures at the hyphal tip, imaged using the fluorescence dye FM4-64. To test for causes of the slower growth of the RIP plc-1 mutant, we examined its physiological poise compared to wildtype and the KO plc-1 mutant. The electrical properties of all three strains and the electrogenic contribution of the plasma membrane H(+)-ATPase (identified by cyanide inhibition) were the same. Responses to high osmolarity were also similar. However, the RIP plc-1 mutant had a significantly lower turgor, a possible cause of its slower growth. While growth of all three strains was inhibited by the phospholipase C inhibitor 3-nitrocoumarin, the RIP plc-1 mutant did not exhibit hyphal bursting after addition of the inhibitor, observed in both wildtype and the KO plc-1 mutant. Although the plc-1 gene is not obligatory for tip growth, the phenotype of the RIP plc-1 mutant - abnormal tip cytology, lower turgor and resistance to inhibitor-induced hyphal bursting - suggest it does play a role in tip growth. The expression of a dysfunctional plc-1 gene may cause a shift to alternative mechanism(s) of growth sensing in hyphal extension.
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Affiliation(s)
- Roger R Lew
- York University, Biology Department, 4700 Keele Street, Toronto, ON M3J 1P3, Canada.
| | - Rachel E Giblon
- York University, Biology Department, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
| | - Miranda S H Lorenti
- York University, Biology Department, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
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9
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A Cyclic GMP-Dependent K+ Channel in the Blastocladiomycete Fungus Blastocladiella emersonii. EUKARYOTIC CELL 2015; 14:958-63. [PMID: 26150416 DOI: 10.1128/ec.00087-15] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Accepted: 06/30/2015] [Indexed: 12/21/2022]
Abstract
Phototaxis in flagellated zoospores of the aquatic fungus Blastocladiella emersonii depends on a novel photosensor, Blastocladiella emersonii GC1 (BeGC1), comprising a type I (microbial) rhodopsin fused to a guanylyl cyclase catalytic domain, that produces the conserved second messenger cyclic GMP (cGMP). The rapid and transient increase in cGMP levels during the exposure of zoospores to green light was shown to be necessary for phototaxis and dependent on both rhodopsin function and guanylyl cyclase activity. It is noteworthy that BeGC1 was localized to the zoospore eyespot apparatus, in agreement with its role in the phototactic response. A putative cyclic nucleotide-gated channel (BeCNG1) was also identified in the genome of the fungus and was implicated in flagellar beating via the action of a specific inhibitor (l-cis-diltiazem) that compromised zoospore motility. Here we show that B. emersonii expresses a K(+) channel that is activated by cGMP. The use of specific channel inhibitors confirmed the activation of the channel by cGMP and its K(+) selectivity. These characteristics are consistent with the function of an ion channel encoded by the BeCNG1 gene. Other blastocladiomycete fungi, such as Allomyces macrogynus and Catenaria anguillulae, possess genes encoding a similar K(+) channel and the rhodopsin-guanylyl cyclase fusion protein, while the genes encoding both these proteins are absent in nonflagellated fungi. The presence of these genes as a pair seems to be an exclusive feature of blastocladiomycete fungi. Taken together, these data demonstrate that the B. emersonii cGMP-activated K(+) channel is involved in the control of zoospore motility, most probably participating in the cGMP-signaling pathway for the phototactic response of the fungus.
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10
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Križak S, Nikolić L, Stanić M, Žižić M, Zakrzewska J, Živić M, Todorović N. Osmotic swelling activates a novel anionic current with VRAC-like properties in a cytoplasmic droplet membrane from Phycomyces blakesleeanus sporangiophores. Res Microbiol 2015; 166:162-73. [DOI: 10.1016/j.resmic.2015.02.004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2014] [Revised: 02/05/2015] [Accepted: 02/07/2015] [Indexed: 02/05/2023]
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11
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Potapova TV. Structural and functional organization of growing tips of Neurospora crassa Hyphae. BIOCHEMISTRY (MOSCOW) 2014; 79:593-607. [PMID: 25108323 DOI: 10.1134/s0006297914070025] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Data are presented on a variety of intracellular structures of the vegetative hyphae of the filamentous fungus Neurospora crassa and the involvement of these structures in the tip growth of the hyphae. Current ideas on the molecular and genetic mechanisms of tip growth and regulation of this process are considered. On the basis of comparison of data on behaviors of mitochondria and microtubules and data on the electrical heterogeneity of the hyphal apex, a hypothesis is proposed about a possible supervisory role of the longitudinal electric field in the structural and functional organization of growing tips of the N. crassa hyphae.
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Affiliation(s)
- T V Potapova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, 119991, Russia.
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Muralidhar A, Novis PM, Broady PA, Collings DA, Garrill A. An estuarine species of the alga Vaucheria (Xanthophyceae) displays an increased capacity for turgor regulation when compared to a freshwater species. JOURNAL OF PHYCOLOGY 2013; 49:967-978. [PMID: 27007319 DOI: 10.1111/jpy.12106] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2013] [Accepted: 07/13/2013] [Indexed: 06/05/2023]
Abstract
Turgor regulation is the process by which walled organisms alter their internal osmotic potential to adapt to osmotic changes in the environment. Apart from a few studies on freshwater oomycetes, the ability of stramenopiles to turgor regulate has not been investigated. In this study, turgor regulation and growth were compared in two species of the stramenopile alga Vaucheria, Vaucheria erythrospora isolated from an estuarine habitat, and Vaucheria repens isolated from a freshwater habitat. Species were identified using their rbcL sequences and respective morphologies. Using a single cell pressure probe to directly measure turgor in Vaucheria after hyperosmotic shock, V. erythrospora was found to recover turgor after a larger shock than V. repens. Threshold shock values for this ability were >0.5 MPa for V. erythrospora and <0.5 MPa for V. repens. Recovery was more rapid in V. erythrospora than V. repens after comparable shocks. Turgor recovery in V. erythrospora was inhibited by Gd(3+) and TEA, suggesting a role for mechanosensitive channels, nonselective cation channels, and K(+) channels in the process. Growth studies showed that V. erythrospora was able to grow over a wider range of NaCl concentrations. These responses may underlie the ability of V. erythrospora to survive in an estuarine habitat and restrict V. repens to freshwater. The fact that both species can turgor regulate may indicate a fundamental difference between members of the Stramenopila, as research to date on oomycetes suggests they are unable to turgor regulate.
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Affiliation(s)
- Abishek Muralidhar
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
| | - Phil M Novis
- Allan Herbarium, Landcare Research, P.O. Box 40, Lincoln, 7640, New Zealand
| | - Paul A Broady
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
| | - David A Collings
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
| | - Ashley Garrill
- School of Biological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
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Ordoñez NM, Shabala L, Gehring C, Shabala S. Noninvasive microelectrode ion flux estimation technique (MIFE) for the study of the regulation of root membrane transport by cyclic nucleotides. Methods Mol Biol 2013; 1016:95-106. [PMID: 23681574 DOI: 10.1007/978-1-62703-441-8_7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Changes in ion permeability and subsequently intracellular ion concentrations play a crucial role in intracellular and intercellular communication and, as such, confer a broad array of developmental and adaptive responses in plants. These changes are mediated by the activity of plasma-membrane based transport proteins many of which are controlled by cyclic nucleotides and/or other signaling molecules. The MIFE technique for noninvasive microelectrode ion flux measuring allows concurrent quantification of net fluxes of several ions with high spatial (μm range) and temporal (ca. 5 s) resolution, making it a powerful tool to study various aspects of downstream signaling events in plant cells. This chapter details basic protocols enabling the application of the MIFE technique to study regulation of root membrane transport in general and cyclic nucleotide mediated transport in particular.
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Affiliation(s)
- Natalia Maria Ordoñez
- Division of Chemical and Life Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
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14
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Shabala S, Shabala L, Bose J, Cuin T, Newman I. Ion flux measurements using the MIFE technique. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2013; 953:171-83. [PMID: 23073883 DOI: 10.1007/978-1-62703-152-3_11] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/08/2022]
Abstract
Noninvasive microelectrode ion flux measurements (the MIFE™ technique) allow the concurrent quantification of net fluxes of several ions with high spatial (several μm) and temporal (ca 5 s) resolution. The MIFE technique has become a popular tool for studying the adaptive responses of plant cells and tissues to a large number of abiotic and biotic stresses. This chapter briefly summarizes some key findings on spatial and temporal organization of plant nutrient acquisition obtained by the MIFE technique, as well as the MIFE contribution towards elucidating the mechanisms behind a plant's perception and signaling of major abiotic stresses. The full protocols for microelectrode fabrication, calibration, and use are then given, and two basic routines for mapping root ion flux profiles and studying transient ion flux kinetics are given.
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Affiliation(s)
- Sergey Shabala
- School of Agricultural Science, University of Tasmania, Hobart, Australia.
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15
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Hamam A, Lew RR. Electrical phenotypes of calcium transport mutant strains of a filamentous fungus, Neurospora crassa. EUKARYOTIC CELL 2012; 11:694-702. [PMID: 22408225 PMCID: PMC3346425 DOI: 10.1128/ec.05329-11] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2011] [Accepted: 02/28/2012] [Indexed: 12/27/2022]
Abstract
We characterized the electrical phenotypes of mutants with mutations in genes encoding calcium transporters-a mechanosensitive channel homolog (MscS), a Ca(2+)/H(+) exchange protein (cax), and Ca(2+)-ATPases (nca-1, nca-2, nca-3)-as well as those of double mutants (the nca-2 cax, nca-2 nca-3, and nca-3 cax mutants). The electrical characterization used dual impalements to obtain cable-corrected current-voltage measurements. Only two types of mutants (the MscS mutant; the nca-2 mutant and nca-2-containing double mutants) exhibited lower resting potentials. For the nca-2 mutant, on the basis of unchanged conductance and cyanide-induced depolarization of the potential, the cause is attenuated H(+)-ATPase activity. The growth of the nca-2 mutant-containing strains was inhibited by elevated extracellular Ca(2+) levels, indicative of lesions in Ca(2+) homeostasis. However, the net Ca(2+) effluxes of the nca-2 mutant, measured noninvasively with a self-referencing Ca(2+)-selective microelectrode, were similar to those of the wild type. All of the mutants exhibited osmosensitivity similar to that of the wild type (the turgor of the nca-2 mutant was also similar to that of the wild type), suggesting that Ca(2+) signaling does not play a role in osmoregulation. The hyphal tip morphology and tip-localized mitochondria of the nca-2 mutant were similar to those of the wild type, even when the external [Ca(2+)] was elevated. Thus, although Ca(2+) homeostasis is perturbed in the nca-2 mutant (B. J. Bowman et al., Eukaryot. Cell 10:654-661, 2011), the phenotype does not extend to tip growth or to osmoregulation but is revealed by lower H(+)-ATPase activity.
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Affiliation(s)
- Ahmed Hamam
- Biology Department, York University, Toronto, Ontario, Canada
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16
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Shabala S, Shabala L. Ion transport and osmotic adjustment in plants and bacteria. Biomol Concepts 2011; 2:407-19. [DOI: 10.1515/bmc.2011.032] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2011] [Accepted: 06/29/2011] [Indexed: 01/19/2023] Open
Abstract
AbstractPlants and bacteria respond to hyperosmotic stress by an increase in intracellular osmolality, adjusting their cell turgor to altered growth conditions. This can be achieved either by increased uptake orde novosynthesis of a variety of organic osmolytes (so-called ‘compatible solutes’), or by controlling fluxes of ions across cellular membranes. The relative contributions of each of these mechanisms have been debated in literature for many years and remain unresolved. This paper summarises all the arguments and reopens a discussion on the efficiency and strategies of osmotic adjustment in plants and bacteria. We show that the bulk of osmotic adjustment in both plants and bacteria is achieved by increased accumulation of inorganic osmolytes such as K+, Na+and Cl-. This is applicable to both halophyte and glycophyte species. At the same time,de novosynthesis of compatible solutes is an energetically expensive and slow option and can be used only for the fine adjustment of the cell osmotic potential. The most likely role the organic osmolytes play in osmotic adjustment is in osmoprotection of key membrane transport proteins and reactive oxygen species (ROS) scavenging. The specific mechanisms by which compatible solutes regulate activity of ion transporters remain elusive and require more thorough investigation. It is concluded that creating transgenic species with increased levels of organic osmolytes by itself is counterproductive due to high yield penalties; all these attempts should be complemented by a concurrent increase in the accumulation of inorganic ions directly used for osmotic adjustment.
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Affiliation(s)
- Sergey Shabala
- 1School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, TAS 7001, Australia
| | - Lana Shabala
- 1School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, TAS 7001, Australia
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Benito B, Garciadeblás B, Fraile-Escanciano A, Rodríguez-Navarro A. Potassium and sodium uptake systems in fungi. The transporter diversity of Magnaporthe oryzae. Fungal Genet Biol 2011; 48:812-22. [DOI: 10.1016/j.fgb.2011.03.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Revised: 03/03/2011] [Accepted: 03/03/2011] [Indexed: 10/18/2022]
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Lew RR. How does a hypha grow? The biophysics of pressurized growth in fungi. Nat Rev Microbiol 2011; 9:509-18. [DOI: 10.1038/nrmicro2591] [Citation(s) in RCA: 163] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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Architecture and development of the Neurospora crassa hypha – a model cell for polarized growth. Fungal Biol 2011; 115:446-74. [PMID: 21640311 DOI: 10.1016/j.funbio.2011.02.008] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2010] [Revised: 02/08/2011] [Accepted: 02/09/2011] [Indexed: 11/20/2022]
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Shabala L, McMeekin T, Shabala S. Osmotic adjustment and requirement for sodium in marine protist thraustochytrid. Environ Microbiol 2011; 11:1835-43. [PMID: 20849566 DOI: 10.1111/j.1462-2920.2009.01908.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A non-invasive ion-selective microelectrode technique was used to elucidate the ionic mechanisms of osmotic adjustment in a marine protist thraustochytrid. Hypoosmotic stress caused significant efflux of Na(+), Cl(-) and K(+) from thraustochytrid cells. Model calculations showed that almost complete osmotic adjustment was achieved within the first 30 min after stress onset. Of these, sodium was the major contributor (more than half of the total osmotic adjustment), with chloride being the second major contributor. The role of K(+) in the process of osmotic adjustment was relatively small. Changes in Ca(2+) and H(+) flux were attributed to intracellular signalling. Ion flux data were confirmed by growth experiments. Thraustochytrium cells showed normal growth patterns even when grown in a sodium-free solution provided the medium osmolality was adjusted by mannitol to one of the seawater. That suggests that the requirement of sodium for thraustochytrid growth cycle is due to its role in cell osmotic adjustment rather than because of the direct Na(+) involvement in cell metabolism. Altogether, these data demonstrate the evidence for turgor regulation in thraustochytrids and suggest that these cells may be grown in the absence of sodium providing that cell turgor is adjusted by some other means.
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Affiliation(s)
- Lana Shabala
- School of Agricultural Science, University of Tasmania, Private Bag 54, Hobart, Tas. 7001, Australia
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21
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Oide S, Liu J, Yun SH, Wu D, Michev A, Choi MY, Horwitz BA, Turgeon BG. Histidine kinase two-component response regulator proteins regulate reproductive development, virulence, and stress responses of the fungal cereal pathogens Cochliobolus heterostrophus and Gibberella zeae. EUKARYOTIC CELL 2010; 9:1867-80. [PMID: 21037181 PMCID: PMC3008274 DOI: 10.1128/ec.00150-10] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2010] [Accepted: 10/15/2010] [Indexed: 01/04/2023]
Abstract
Histidine kinase (HK) phosphorelay signaling is a major mechanism by which fungi sense their environment. The maize pathogen Cochliobolus heterostrophus has 21 HK genes, 4 candidate response regulator (RR) genes (SSK1, SKN7, RIM15, REC1), and 1 gene (HPT1) encoding a histidine phosphotransfer domain protein. Because most HKs are expected to signal through RRs, these were chosen for deletion. Except for pigment and slight growth alterations for rim15 mutants, no measurable altered phenotypes were detected in rim15 or rec1 mutants. Ssk1p is required for virulence and affects fertility and proper timing of sexual development of heterothallic C. heterostrophus. Pseudothecia from crosses involving ssk1 mutants ooze masses of single ascospores, and tetrads cannot be found. Wild-type pseudothecia do not ooze. Ssk1p represses asexual spore proliferation during the sexual phase, and lack of it dampens asexual spore proliferation during vegetative growth, compared to that of the wild type. ssk1 mutants are heavily pigmented. Mutants lacking Skn7p do not display any of the above phenotypes; however, both ssk1 and skn7 mutants are hypersensitive to oxidative and osmotic stresses and ssk1 skn7 mutants are more exaggerated in their spore-type balance phenotype and more sensitive to stress than single mutants. ssk1 mutant phenotypes largely overlap hog1 mutant phenotypes, and in both types of mutant, the Hog1 target gene, MST1, is not induced. ssk1 and hog1 mutants were examined in the homothallic cereal pathogen Gibberella zeae, and pathogenic and reproductive phases of development regulated by Ssk1 and Hog1 were found to mirror, but also vary from, those of C. heterostrophus.
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Affiliation(s)
- Shinichi Oide
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York
| | - Jinyuan Liu
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York
| | - Sung-Hwan Yun
- Department of Medical Biotechnology, Soonchunhyang University, Asan, South Korea
| | - Dongliang Wu
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York
| | - Alex Michev
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York
| | - May Yee Choi
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York
| | | | - B. Gillian Turgeon
- Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, New York
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Lew RR. Turgor and net ion flux responses to activation of the osmotic MAP kinase cascade by fludioxonil in the filamentous fungus Neurospora crassa. Fungal Genet Biol 2010; 47:721-6. [PMID: 20546911 DOI: 10.1016/j.fgb.2010.05.007] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2010] [Revised: 05/16/2010] [Accepted: 05/17/2010] [Indexed: 10/19/2022]
Abstract
The internal hydrostatic pressure (turgor) of the filamentous fungus Neurospora crassa is regulated at about 400-500 kiloPascals, primarily by an osmotic MAP kinase cascade which activates ion uptake from the extracellular medium and glycerol synthesis. In the absence of hyperosmotic stress, the phenylpyrrole fungicide fludioxonil activates the osmotic MAP kinase cascade, resulting in cell death. Turgor, the electrical potential and net ion fluxes were measured after treatment with fludioxonil. In wildtype, fludioxonil causes a hyperpolarization of the plasma membrane and net H(+) efflux from the cell, consistent with activation of the H(+)-ATPase. At the same time, net K(+) uptake occurs, and turgor increases (about 2-fold above normal levels). None of these changes are observed in the os-2 mutant (which lacks a functional MAP kinase, the last of the three kinases in the osmotic MAP kinase cascade). Tip growth ceases as hyperpolarization, net ion flux changes, and turgor increases begin. The inappropriate turgor increase is the probable cause of eventual lysis and death. The results corroborate a multi-pathway response to hyperosmotic stress that includes activation of plasma membrane transport. The relation to cell expansion (tip growth) is not direct. Increases in turgor due to ion transport might be expected to increase growth rate, but this does not occur. Instead, there must be a complex regulatory interplay between the growth and the turgor driving force, possibly mediated by regulation of cell wall extensibility.
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Affiliation(s)
- Roger R Lew
- Department of Biology, York University, Toronto, Ontario, Canada.
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23
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Lew RR, Kapishon V. Ptk2 contributes to osmoadaptation in the filamentous fungus Neurospora crassa. Fungal Genet Biol 2009; 46:949-55. [PMID: 19772928 DOI: 10.1016/j.fgb.2009.09.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2009] [Revised: 09/17/2009] [Accepted: 09/17/2009] [Indexed: 10/20/2022]
Abstract
Hyphal tip-growing organisms often rely upon an internal hydrostatic pressure (turgor) to drive localized expansion of the cell. Regulation of the turgor in response to osmotic shock is mediated primarily by an osmotic MAP kinase cascade which activates osmolyte synthesis and ion uptake to effect turgor recovery. We characterized a Neurospora crassa homolog (PTK2) of ser/thr kinase regulators of ion transport in yeast to determine its role in turgor regulation in a filamentous fungi. The ptk2 mutant is osmosensitive, and has lower turgor poise than wildtype. The cause appears to be lower activity of the plasma membrane H+-ATPase. Its role in osmoadaptation is unrelated to the activity of the osmotic MAP kinase cascade. Instead, it acts in an alternative pathway that, like the osmotic MAP kinase cascade, also involves ion transport mediated osmoadaptation.
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Affiliation(s)
- Roger R Lew
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario M3J1P3, Canada.
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Lew RR, Nasserifar S. Transient responses during hyperosmotic shock in the filamentous fungus Neurospora crassa. MICROBIOLOGY-SGM 2009; 155:903-911. [PMID: 19246761 DOI: 10.1099/mic.0.023507-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Fungal cells maintain an internal hydrostatic pressure (turgor) of about 400-500 kPa. In the filamentous fungus Neurospora crassa, the initial cellular responses to hyperosmotic treatment are loss of turgor, a decrease in relative hyphal volume per unit length (within 1 min) and cell growth arrest; all recover over a period of 10-60 min due to increased net ion uptake and glycerol production. The electrical responses to hyperosmotic treatment are a transient depolarization of the potential (within 1 min), followed by a sustained hyperpolarization (after 4 min) to a potential more negative than the initial potential (a driving force for ion uptake). The nature of the transient depolarization was explored in the context of other transient responses to hyperosmotic shock, to determine whether activation of a specific ion permeability or some other rapid change in electrogenic transport was responsible. Changing the ionic composition of the extracellular medium revealed that K(+) permeability increases and H(+) permeability declines during the transient depolarization. We suggest that these changes are due to concerted inhibition of the electrogenic H(+)-ATPase, and an increase in a K(+) conductance. Knockout mutants of known K(+) (tok, trk, trm-8, hak-1) and Cl(-) (a clc-3 homologue) channels and transporters had no effect on the transient depolarization, but trk and hak-1 do play a role in osmoadaptation, as does a homologue of a serine kinase regulator of H(+)-ATPase in yeast, Ptk2.
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Affiliation(s)
- Roger R Lew
- Department of Biology, York University, Toronto ON M3J 1P3, Canada
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Lew RR, Abbas Z, Anderca MI, Free SJ. Phenotype of a mechanosensitive channel mutant, mid-1, in a filamentous fungus, Neurospora crassa. EUKARYOTIC CELL 2008; 7:647-55. [PMID: 18296620 PMCID: PMC2292622 DOI: 10.1128/ec.00411-07] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2007] [Accepted: 02/12/2008] [Indexed: 12/21/2022]
Abstract
In the yeast Saccharomyces cerevisiae, the MID1 (mating-induced death) gene encodes a stretch-activated channel which is required for successful mating; the mutant phenotype is rescued by elevated extracellular calcium. Homologs of the MID1 gene are found in fungi that are morphologically complex compared to yeast, both Basidiomycetes and Ascomycetes. We explored the phenotype of a mid-1 knockout mutant in the filamentous ascomycete Neurospora crassa. The mutant exhibits lower growth vigor than the wild type (which is not rescued by replete calcium) and mates successfully. Thus, the role of the MID-1 protein differs from that of the homologous gene product in yeast. Hyphal cytology, growth on diverse carbon sources, turgor regulation, and circadian rhythms of the mid-1 mutant are all similar to those of the wild type. However, basal turgor is lower than wild type, as is the activity of the plasma membrane H(+)-ATPase (measured by cyanide [CN(-)]-induced depolarization of the energy-dependent component of the membrane potential). In addition, the mutant is unable to grow at low extracellular Ca(2+) levels or when cytoplasmic Ca(2+) is elevated with the Ca(2+) ionophore A23187. We conclude that the MID-1 protein plays a role in regulation of ion transport via Ca(2+) homeostasis and signaling. In the absence of normal ion transport activity, the mutant exhibits poorer growth.
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Affiliation(s)
- Roger R Lew
- Department of Biology, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
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Lew RR, Levina NN. Turgor regulation in the osmosensitive cut mutant of Neurospora crassa. MICROBIOLOGY-SGM 2007; 153:1530-1537. [PMID: 17464067 DOI: 10.1099/mic.0.2006/004085-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The internal hydrostatic pressure (turgor) of fungal cells is maintained at 400-500 kPa. The turgor is regulated by changes in ion flux and by production of the osmotically active metabolite glycerol. In Neurospora crassa, there are at least two genetically distinct pathways that function in adaptation to hyperosmotic shock. One involves a mitogen-activated protein (MAP) kinase cascade (kinases OS-4, OS-5 and OS-2 downstream of the osmosensing OS-1); the other is less understood, but involves the cut gene, which encodes a putative phosphatase. This study examined turgor regulation, electrical responses, ion fluxes and glycerol accumulation in the cut mutant. Turgor recovery after hyperosmotic treatment was similar to that in the wild-type, for both time-course ( approximately 40 min) and magnitude. Prior to turgor recovery, the hyperosmotic shock caused a rapid transient depolarization of the membrane potential, followed by a sustained hyperpolarization that occurred concomitant with increased H(+) efflux, indicating that the plasma membrane H(+)-ATPase was being activated. These changes also occurred in the wild-type. Net fluxes of Ca(2+) and Cl(-) during turgor recovery were similar to those in the wild-type, but K(+) influx was attenuated in the cut mutant. The similar turgor recovery can be explained by the ion uptake, since glycerol did not accumulate in the cut mutant within the time frame of turgor recovery (but did accumulate in the wild-type). The results suggest that turgor regulation involves multi-faceted coordination of both ion flux and glycerol accumulation. Ion uptake is activated by a MAP kinase cascade, while CUT is required for glycerol accumulation.
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Affiliation(s)
- Roger R Lew
- Department of Biology, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
| | - Natalia N Levina
- Department of Biology, York University, 4700 Keele Street, Toronto, ON M3J 1P3, Canada
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28
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Jones CA, Greer-Phillips SE, Borkovich KA. The response regulator RRG-1 functions upstream of a mitogen-activated protein kinase pathway impacting asexual development, female fertility, osmotic stress, and fungicide resistance in Neurospora crassa. Mol Biol Cell 2007; 18:2123-36. [PMID: 17392518 PMCID: PMC1877117 DOI: 10.1091/mbc.e06-03-0226] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Two-component systems, consisting of proteins with histidine kinase and/or response regulator domains, regulate environmental responses in bacteria, Archaea, fungi, slime molds, and plants. Here, we characterize RRG-1, a response regulator protein from the filamentous fungus Neurospora crassa. The cell lysis phenotype of Delta rrg-1 mutants is reminiscent of osmotic-sensitive (os) mutants, including nik-1/os-1 (a histidine kinase) and strains defective in components of a mitogen-activated protein kinase (MAPK) pathway: os-4 (MAPK kinase kinase), os-5 (MAPK kinase), and os-2 (MAPK). Similar to os mutants, Delta rrg-1 strains are sensitive to hyperosmotic conditions, and they are resistant to the fungicides fludioxonil and iprodione. Like os-5, os-4, and os-2 mutants, but in contrast to nik-1/os-1 strains, Delta rrg-1 mutants do not produce female reproductive structures (protoperithecia) when nitrogen starved. OS-2-phosphate levels are elevated in wild-type cells exposed to NaCl or fludioxonil, but they are nearly undetectable in Delta rrg-1 strains. OS-2-phosphate levels are also low in Delta rrg-1, os-2, and os-4 mutants under nitrogen starvation. Analysis of the rrg-1(D921N) allele, mutated in the predicted phosphorylation site, provides support for phosphorylation-dependent and -independent functions for RRG-1. The data indicate that RRG-1 controls vegetative cell integrity, hyperosmotic sensitivity, fungicide resistance, and protoperithecial development through regulation of the OS-4/OS-5/OS-2 MAPK pathway.
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Affiliation(s)
- Carol A. Jones
- *Department of Plant Pathology and Microbiology and
- Program in Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA 92521
| | | | - Katherine A. Borkovich
- *Department of Plant Pathology and Microbiology and
- Program in Biochemistry and Molecular Biology, University of California, Riverside, Riverside, CA 92521
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Zonia L, Munnik T. Life under pressure: hydrostatic pressure in cell growth and function. TRENDS IN PLANT SCIENCE 2007; 12:90-7. [PMID: 17293155 DOI: 10.1016/j.tplants.2007.01.006] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2006] [Revised: 01/02/2007] [Accepted: 01/31/2007] [Indexed: 05/08/2023]
Abstract
H(2)O is one of the most essential molecules for cellular life. Cell volume, osmolality and hydrostatic pressure are tightly controlled by multiple signaling cascades and they drive crucial cellular functions ranging from exocytosis and growth to apoptosis. Ion fluxes and cell shape restructuring induce asymmetries in osmotic potential across the plasma membrane and lead to localized hydrodynamic flow. Cells have evolved fascinating strategies to harness the potential of hydrodynamic flow to perform crucial functions. Plants exploit hydrodynamics to drive processes including gas exchange, leaf positioning, nutrient acquisition and growth. This paradigm is extended by recent work that reveals an important role for hydrodynamics in pollen tube growth.
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Affiliation(s)
- Laura Zonia
- Department of Plant Physiology, Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 318, 1098 SM Amsterdam, Netherlands.
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