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Developing a Temperature-Inducible Transcriptional Rheostat in Neurospora crassa. mBio 2023; 14:e0329122. [PMID: 36744948 PMCID: PMC9973361 DOI: 10.1128/mbio.03291-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Heat shock protein (HSP)-encoding genes (hsp), part of the highly conserved heat shock response (HSR), are known to be induced by thermal stress in several organisms. In Neurospora crassa, three hsp genes, hsp30, hsp70, and hsp80, have been characterized; however, the role of defined cis elements in their responses to discrete changes in temperature remains largely unexplored. To fill this gap, while also aiming to obtain a reliable fungal heat shock-inducible system, we analyzed different sections of each hsp promoter by assessing the expression of real-time transcriptional reporters. Whereas all three promoters and their resected versions were acutely induced by high temperatures, only hsp30 displayed a broad range of expression and high tunability, amply exceeding other inducible promoter systems existing in Neurospora, such as quinic acid- or light-inducible ones. As proof of concept, we employed one of these promoters to control the expression of clr-2, which encodes the master regulator of Neurospora cellulolytic capabilities. The resulting strain fails to grow on cellulose at 25°C, whereas it grows robustly if heat shock pulses are delivered daily. Additionally, we designed two hsp30 synthetic promoters and characterized them, as well as the native promoters, using a gradient of high temperatures, yielding a wide range of responses to thermal stimuli. Thus, Neurospora hsp30-based promoters represent a new set of modular elements that can be used as transcriptional rheostats to adjust the expression of a gene of interest or for the implementation of regulated circuitries for synthetic biology and biotechnological strategies. IMPORTANCE A timely and dynamic response to strong temperature fluctuations is paramount for organismal biology. At the same time, inducible promoters are a powerful tool for fungal biotechnological and synthetic biology endeavors. In this work, we analyzed the activity of several N. crassa heat shock protein (hsp) promoters at a wide range of temperatures, observing that hsp30 exhibits remarkable sensitivity and a dynamic range of expression as we charted the response of this promoter to subtle increases in temperature, and also as we built and analyzed synthetic promoters based on hsp30 cis elements. As proof of concept, we tested the ability of hsp30 to provide tight control of a central process, cellulose degradation. While this study provides an unprecedented description of the regulation of the N. crassa hsp genes, it also contributes a noteworthy addition to the molecular toolset of transcriptional controllers in filamentous fungi.
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Cabrera IE, Oza Y, Carrillo AJ, Collier LA, Wright SJ, Li L, Borkovich KA. Regulator of G Protein Signaling Proteins Control Growth, Development and Cellulase Production in Neurospora crassa. J Fungi (Basel) 2022; 8:jof8101076. [PMID: 36294641 PMCID: PMC9604755 DOI: 10.3390/jof8101076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 10/05/2022] [Accepted: 10/11/2022] [Indexed: 11/30/2022] Open
Abstract
Heterotrimeric (αβγ) G protein signaling pathways are critical environmental sensing systems found in eukaryotic cells. Exchange of GDP for GTP on the Gα subunit leads to its activation. In contrast, GTP hydrolysis on the Gα is accelerated by Regulator of G protein Signaling (RGS) proteins, resulting in a return to the GDP-bound, inactive state. Here, we analyzed growth, development and extracellular cellulase production in strains with knockout mutations in the seven identified RGS genes (rgs-1 to rgs-7) in the filamentous fungus, Neurospora crassa. We compared phenotypes to those of strains with either knockout mutations or expressing predicted constitutively activated, GTPase-deficient alleles for each of the three Gα subunit genes (gna-1Q204L, gna-2Q205L or gna-3Q208L). Our data revealed that six RGS mutants have taller aerial hyphae than wild type and all seven mutants exhibit reduced asexual sporulation, phenotypes shared with strains expressing the gna-1Q204L or gna-3Q208L allele. In contrast, Δrgs-1 and Δrgs-3 were the only RGS mutants with a slower growth rate phenotype, a defect in common with gna-1Q204L strains. With respect to female sexual development, Δrgs-1 possessed defects most similar to gna-3Q208L strains, while those of Δrgs-2 mutants resembled strains expressing the gna-1Q204L allele. Finally, we observed that four of the seven RGS mutants had significantly different extracellular cellulase levels relative to wild type. Of interest, the Δrgs-2 mutant had no detectable activity, similar to the gna-3Q208L strain. In contrast, the Δrgs-1 and Δrgs-4 mutants and gna-1Q204L and gna-2Q205L strains exhibited significantly higher cellulase activity than wild type. With the exception of sexual development, our results demonstrate the greatest number of genetic interactions between rgs-1 and gna-1 and rgs-2 and gna-3 in N. crassa.
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Regulation of Hsp80 involved in the acquisition of induced thermotolerance, and NCA-2 involved in calcium stress tolerance by the calcineurin-CRZ-1 signaling pathway in Neurospora crassa. Mycol Prog 2022. [DOI: 10.1007/s11557-022-01833-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Carrillo AJ, Halilovic L, Hur M, Kirkwood JS, Borkovich KA. Targeted Metabolomics Using LC-MS in Neurospora crassa. Curr Protoc 2022; 2:e454. [PMID: 35616476 DOI: 10.1002/cpz1.454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The filamentous fungus Neurospora crassa has historically been a model for understanding the relationship between genes and metabolism-auxotrophic mutants of N. crassa were used by Beadle and Tatum to develop the one-gene-one-enzyme hypothesis for which they earned the Nobel Prize in 1958. In the ensuing decades, several techniques have been developed for the systematic analysis of metabolites in N. crassa and other fungi. Untargeted and targeted approaches have been used, with a focus on secondary metabolites over primary metabolism. Here, we describe a pipeline for sample preparation, metabolite extraction, Liquid Chromatography-Mass Spectrometry (LC-MS), and data analysis that can be used for targeted metabolomics of primary metabolites in N. crassa. Liquid cultures are grown with shaking in a defined minimal medium and then collected using filtration. Samples are lyophilized for 2 days at -80°C, pulverized, and mixed with a solution to extract polar metabolites. The metabolites are separated and identified using LC-MS, with downstream analysis using Skyline interpretive software. Relative levels of hundreds of metabolites can be detected and compared across strains. © 2022 Wiley Periodicals LLC. Basic Protocol: Metabolite extraction and detection from Neurospora crassa cell cultures using Liquid Chromatography-Mass Spectrometry.
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Affiliation(s)
- Alexander J Carrillo
- Department of Microbiology and Plant Pathology, University of California, Riverside, California
| | - Lida Halilovic
- Department of Microbiology and Plant Pathology, University of California, Riverside, California
| | - Manhoi Hur
- Institute for Integrative Genome Biology Metabolomics Core, University of California, Riverside, California
| | - Jay S Kirkwood
- Institute for Integrative Genome Biology Metabolomics Core, University of California, Riverside, California
| | - Katherine A Borkovich
- Department of Microbiology and Plant Pathology, University of California, Riverside, California
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Garud A, Carrillo AJ, Collier LA, Ghosh A, Kim JD, Lopez-Lopez B, Ouyang S, Borkovich KA. Genetic relationships between the RACK1 homolog cpc-2 and heterotrimeric G protein subunit genes in Neurospora crassa. PLoS One 2019; 14:e0223334. [PMID: 31581262 PMCID: PMC6776386 DOI: 10.1371/journal.pone.0223334] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2019] [Accepted: 09/18/2019] [Indexed: 11/19/2022] Open
Abstract
Receptor for Activated CKinase-1 (RACK1) is a multifunctional eukaryotic scaffolding protein with a seven WD repeat structure. Among their many cellular roles, RACK1 homologs have been shown to serve as alternative Gβ subunits during heterotrimeric G protein signaling in many systems. We investigated genetic interactions between the RACK1 homolog cpc-2, the previously characterized Gβ subunit gnb-1 and other G protein signaling components in the multicellular filamentous fungus Neurospora crassa. Results from cell fractionation studies and from fluorescent microscopy of a strain expressing a CPC-2-GFP fusion protein revealed that CPC-2 is a cytoplasmic protein. Genetic epistasis experiments between cpc-2, the three Gα genes (gna-1, gna-2 and gna-3) and gnb-1 demonstrated that cpc-2 is epistatic to gna-2 with regards to basal hyphae growth rate and aerial hyphae height, while deletion of cpc-2 mitigates the increased macroconidiation on solid medium observed in Δgnb-1 mutants. Δcpc-2 mutants inappropriately produce conidiophores during growth in submerged culture and mutational activation of gna-3 alleviates this defect. Δcpc-2 mutants are female-sterile and fertility could not be restored by mutational activation of any of the three Gα genes. With the exception of macroconidiation on solid medium, double mutants lacking cpc-2 and gnb-1 exhibited more severe defects for all phenotypic traits, supporting a largely synergistic relationship between GNB-1 and CPC-2 in N. crassa.
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Affiliation(s)
- Amruta Garud
- Department of Microbiology and Plant Pathology, University of California, Riverside, California, United States of America
| | - Alexander J. Carrillo
- Department of Microbiology and Plant Pathology, University of California, Riverside, California, United States of America
| | - Logan A. Collier
- Department of Microbiology and Plant Pathology, University of California, Riverside, California, United States of America
| | - Arit Ghosh
- Department of Microbiology and Plant Pathology, University of California, Riverside, California, United States of America
| | - James D. Kim
- Department of Microbiology and Plant Pathology, University of California, Riverside, California, United States of America
| | - Berenise Lopez-Lopez
- Department of Microbiology and Plant Pathology, University of California, Riverside, California, United States of America
| | - Shouqiang Ouyang
- Department of Microbiology and Plant Pathology, University of California, Riverside, California, United States of America
| | - Katherine A. Borkovich
- Department of Microbiology and Plant Pathology, University of California, Riverside, California, United States of America
- * E-mail:
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Gohain D, Tamuli R. Calcineurin responsive zinc-finger-1 binds to a unique promoter sequence to upregulate neuronal calcium sensor-1, whose interaction with MID-1 increases tolerance to calcium stress in Neurospora crassa. Mol Microbiol 2019; 111:1510-1528. [PMID: 30825330 DOI: 10.1111/mmi.14234] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/26/2019] [Indexed: 01/24/2023]
Abstract
We studied the molecular mechanism of neuronal calcium sensor-1 (NCS-1) signaling pathway for tolerance to Ca2+ stress in Neurospora crassa. Increasing concentration of Ca2+ increased the expression of ncs-1; however, the calcineurin inhibitor FK506 severely reduced ncs-1 mRNA transcript levels. Chromatin immunoprecipitation (ChIP) studies revealed that the transcription factor calcineurin responsive zinc finger-1 (CRZ-1) binds to the ncs-1 promoter, and CRZ-1 binding upregulated ncs-1 expression under high Ca2+ concentrations. These results suggested the regulation of NCS-1 function through calcineurin- CRZ-1 signaling pathway. Furthermore, the electrophoretic mobility shift assay (EMSA) revealed that the CRZ-1 binds specifically to an 8 bp sequence 5'-CCTTCACA-3' in the ncs-1 promoter 216 bp upstream of the ATG start codon. We also showed that NCS-1 binds to the Ca2+ permeable channel MID-1 for tolerance to Ca2+ stress. Therefore, CRZ-1 binds to a unique sequence in the ncs-1 promoter, causing upregulation of NCS-1 that binds to MID-1 for tolerance to Ca2+ stress.
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Affiliation(s)
- Dibakar Gohain
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781 039, Assam, India
| | - Ranjan Tamuli
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, 781 039, Assam, India
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Liu G, Qu Y. Engineering of filamentous fungi for efficient conversion of lignocellulose: Tools, recent advances and prospects. Biotechnol Adv 2018; 37:519-529. [PMID: 30576717 DOI: 10.1016/j.biotechadv.2018.12.004] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 12/13/2018] [Accepted: 12/14/2018] [Indexed: 01/17/2023]
Abstract
Filamentous fungi, as the main producers of lignocellulolytic enzymes in industry, need to be engineered to improve the economy of large-scale lignocellulose conversion. Investigation of the cellular processes involved in lignocellulolytic enzyme production, as well as optimization of enzyme mixtures for higher hydrolysis efficiency, have provided effective targets for the engineering of lignocellulolytic fungi. Recently, the development of efficient genetic manipulation systems in several lignocellulolytic fungi opens up the possibility of systems engineering of these strains. Here, we review the recent progresses made in the engineering of lignocellulolytic fungi and highlight the research gaps in this area.
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Affiliation(s)
- Guodong Liu
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China; Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
| | - Yinbo Qu
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao 266237, China; National Glycoengineering Research Center, Shandong University, Qingdao 266237, China.
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Fuller KK, Dunlap JC, Loros JJ. Light-regulated promoters for tunable, temporal, and affordable control of fungal gene expression. Appl Microbiol Biotechnol 2018; 102:3849-3863. [PMID: 29569180 DOI: 10.1007/s00253-018-8887-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Revised: 02/19/2018] [Accepted: 02/20/2018] [Indexed: 01/08/2023]
Abstract
Regulatable promoters are important genetic tools, particularly for assigning function to essential and redundant genes. They can also be used to control the expression of enzymes that influence metabolic flux or protein secretion, thereby optimizing product yield in bioindustry. This review will focus on regulatable systems for use in filamentous fungi, an important group of organisms whose members include key research models, devastating pathogens of plants and animals, and exploitable cell factories. Though we will begin by cataloging those promoters that are controlled by nutritional or chemical means, our primary focus will rest on those who can be controlled by a literal flip-of-the-switch: promoters of light-regulated genes. The vvd promoter of Neurospora will first serve as a paradigm for how light-driven systems can provide tight, robust, tunable, and temporal control of either autologous or heterologous fungal proteins. We will then discuss a theoretical approach to, and practical considerations for, the development of such promoters in other species. To this end, we have compiled genes from six previously published light-regulated transcriptomic studies to guide the search for suitable photoregulatable promoters in your fungus of interest.
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Affiliation(s)
- Kevin K Fuller
- Department of Molecular and Systems Biology, Geisel School of Medicine, Hanover, NH, USA.
| | - Jay C Dunlap
- Department of Molecular and Systems Biology, Geisel School of Medicine, Hanover, NH, USA
| | - Jennifer J Loros
- Department of Molecular and Systems Biology, Geisel School of Medicine, Hanover, NH, USA. .,Department of Biochemistry and Cell Biology, Geisel School of Medicine, Hanover, NH, USA.
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Dinges MM, Lytle C, Larive CK. 1H NMR-Based Identification of Intestinally Absorbed Metabolites by Ussing Chamber Analysis of the Rat Cecum. Anal Chem 2018; 90:4196-4202. [PMID: 29474787 DOI: 10.1021/acs.analchem.8b00393] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The large intestine (cecum and colon) is a complex biochemical factory of vital importance to human health. It plays a major role in digestion and absorption by salvaging nutrients from polysaccharides via fermentation initiated by the bacteria that comprise the gut microbiome. We hypothesize that the intestinal epithelium absorbs a limited number of luminal metabolites with bioactive potential while actively excluding those with toxic effects. To explore this concept, we combined 1H NMR detection with Ussing chamber measurements of absorptive transport by rat cecum. Numerous metabolites transported across the epithelium can be measured simultaneously by 1H NMR, a universal detector of organic compounds, alleviating the need for fluorescent or radiolabeled compounds. Our results demonstrate the utility of this approach to delineate the repertoire of fecal solutes that are selectively absorbed by the cecum and to determine their transport rates.
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Affiliation(s)
- Meredith M Dinges
- Department of Chemistry , University of California , Riverside , California 92521 , United States
| | - Christian Lytle
- School of Medicine , University of California , 900 University Avenue Riverside , California 92521 , United States
| | - Cynthia K Larive
- Department of Chemistry , University of California , Riverside , California 92521 , United States
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Hu C, Zhou M, Wang W, Sun X, Yarden O, Li S. Abnormal Ergosterol Biosynthesis Activates Transcriptional Responses to Antifungal Azoles. Front Microbiol 2018; 9:9. [PMID: 29387050 PMCID: PMC5776110 DOI: 10.3389/fmicb.2018.00009] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Accepted: 01/05/2018] [Indexed: 12/20/2022] Open
Abstract
Fungi transcriptionally upregulate expression of azole efflux pumps and ergosterol biosynthesis pathway genes when exposed to antifungal agents that target ergosterol biosynthesis. To date, these transcriptional responses have been shown to be dependent on the presence of the azoles and/or depletion of ergosterol. Using an inducible promoter to regulate Neurospora crassa erg11, which encodes the major azole target, sterol 14α-demethylase, we were able to demonstrate that the CDR4 azole efflux pump can be transcriptionally activated by ergosterol biosynthesis inhibition even in the absence of azoles. By analyzing ergosterol deficient mutants, we demonstrate that the transcriptional responses by cdr4 and, unexpectedly, genes encoding ergosterol biosynthesis enzymes (erg genes) that are responsive to azoles, are not dependent on ergosterol depletion. Nonetheless, deletion of erg2, which encodes C-8 sterol isomerase, also induced expression of cdr4. Deletion of erg2 also induced the expression of erg24, the gene encoding C-14 sterol reductase, but not other tested erg genes which were responsive to erg11 inactivation. This indicates that inhibition of specific steps of ergosterol biosynthesis can result in different transcriptional responses, which is further supported by our results obtained using different ergosterol biosynthesis inhibitors. Together with the sterol profiles, these results suggest that the transcriptional responses by cdr4 and erg genes are associated with accumulation of specific sterol intermediate(s). This was further supported by the fact that when the erg2 mutant was treated with ketoconazole, upstream inhibition overrode the effects by downstream inhibition on ergosterol biosynthesis pathway. Even though cdr4 expression is associated with the accumulation of sterol intermediates, intra- and extracellular sterol analysis by HPLC-MS indicated that the transcriptional induction of cdr4 did not result in efflux of the accumulated intermediate(s). This study demonstrates, by detailed genetic and chemical analysis, that transcriptional responses by a major efflux pump and genes of the ergosterol biosynthesis pathway to ergosterol biosynthesis inhibitors can be independent of the presence of the drugs and are linked with the accumulation of ergosterol intermediate(s).
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Affiliation(s)
- Chengcheng Hu
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Mi Zhou
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Wenzhao Wang
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
| | - Xianyun Sun
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
| | - Oded Yarden
- Department of Plant Pathology and Microbiology, The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel
| | - Shaojie Li
- State Key Laboratory of Mycology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.,College of Life Sciences, University of Chinese Academy of Sciences, Beijing, China
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Laxmi V, Tamuli R. The calmodulin gene in Neurospora crassa is required for normal vegetative growth, ultraviolet survival, and sexual development. Arch Microbiol 2016; 199:531-542. [PMID: 27888323 DOI: 10.1007/s00203-016-1319-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Revised: 11/02/2016] [Accepted: 11/07/2016] [Indexed: 02/06/2023]
Abstract
We isolated a Neurospora crassa mutant of the calmodulin (cmd) gene using repeat-induced point mutation and studied its phenotypes. The cmd RIP mutant showed a defect in growth, reduced aerial hyphae, decreased carotenoid accumulation, a severe reduction in viability upon ultraviolet (UV) irradiation, and a fertility defect. Moreover, meiotic silencing of the cmd gene resulted in a barren phenotype. In addition, we also performed site-directed mutational analysis of the calcium/calmodulin-dependent kinase-2 (Ca2+/CaMK-2), a target of the CaM protein encoded by the cmd gene. The camk-2 S247A and the camk-2 T267A mutants in a homozygous cross, or in a cross with a Δcamk-2 mutant, displayed an intermediate phenotype, suggesting that serine 247 and threonine 267 phosphorylation sites of the Ca2+/CaMK-2 are essential for full fertility in N. crassa. Therefore, CaM in N. crassa is required for normal vegetative growth, UV survival, and sexual development. Additionally, serine 247 and threonine 267 phosphorylation sites are important for the Ca2+/CaMK-2 function.
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Affiliation(s)
- Vijya Laxmi
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781 039, India
| | - Ranjan Tamuli
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, Assam, 781 039, India.
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Johns AMB, Love J, Aves SJ. Four Inducible Promoters for Controlled Gene Expression in the Oleaginous Yeast Rhodotorula toruloides. Front Microbiol 2016; 7:1666. [PMID: 27818654 PMCID: PMC5073140 DOI: 10.3389/fmicb.2016.01666] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 10/05/2016] [Indexed: 01/24/2023] Open
Abstract
Rhodotorula (Rhodosporidium) toruloides is an oleaginous yeast with great biotechnological potential, capable of accumulating lipid up to 70% of its dry biomass, and of carotenoid biosynthesis. However, few molecular genetic tools are available for manipulation of this basidiomycete yeast and its high genomic GC content can make routine cloning difficult. We have developed plasmid vectors for transformation of R. toruloides which include elements for Saccharomyces cerevisiae in-yeast assembly; this method is robust to the assembly of GC-rich DNA and of large plasmids. Using such vectors we screened for controllable promoters, and identified inducible promoters from the genes NAR1, ICL1, CTR3, and MET16. These four promoters have independent induction/repression conditions and exhibit different levels and rates of induction in R. toruloides, making them appropriate for controllable transgene expression in different experimental situations. Nested deletions were used to identify regulatory regions in the four promoters, and to delimit the minimal inducible promoters, which are as small as 200 bp for the NAR1 promoter. The NAR1 promoter shows very tight regulation under repressed conditions as determined both by an EGFP reporter gene and by conditional rescue of a leu2 mutant. These new tools facilitate molecular genetic manipulation and controllable gene expression in R. toruloides.
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Affiliation(s)
| | - John Love
- Department of Biosciences, University of Exeter Exeter, UK
| | - Stephen J Aves
- Department of Biosciences, University of Exeter Exeter, UK
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Tamuli R, Deka R, Borkovich KA. Calcineurin Subunits A and B Interact to Regulate Growth and Asexual and Sexual Development in Neurospora crassa. PLoS One 2016; 11:e0151867. [PMID: 27019426 PMCID: PMC4809485 DOI: 10.1371/journal.pone.0151867] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2015] [Accepted: 03/04/2016] [Indexed: 01/26/2023] Open
Abstract
Calcineurin is a calcium/calmodulin dependent protein phosphatase in eukaryotes that consists of a catalytic subunit A and a regulatory subunit B. Previous studies in the filamentous fungus Neurospora crassa had suggested that the catalytic subunit of calcineurin might be an essential protein. We generated N. crassa strains expressing the A (cna-1) and B (cnb-1) subunit genes under the regulation of Ptcu-1, a copper-responsive promoter. In these strains, addition of bathocuproinedisulfonic acid (BCS), a copper chelator, results in induction of cna-1 and cnb-1, while excess Cu2+ represses gene expression. Through analysis of these strains under repressing and inducing conditions, we found that the calcineurin is required for normal growth, asexual development and female fertility in N. crassa. Moreover, we isolated and analyzed cnb-1 mutant alleles generated by repeat-induced point mutation (RIP), with the results further supporting roles for calcineurin in growth and fertility in N. crassa. We demonstrated a direct interaction between the CNA-1 and CNB-1 proteins using an assay system developed to study protein-protein interactions in N. crassa.
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Affiliation(s)
- Ranjan Tamuli
- Department of Plant Pathology and Microbiology, Institute for Integrative Genome Biology, University of California Riverside, Riverside, California, United States of America
- Department of Biosciences and Bioengineering, Indian Institute of Technology Guwahati, Guwahati, India
- * E-mail:
| | - Rekha Deka
- Department of Plant Pathology and Microbiology, Institute for Integrative Genome Biology, University of California Riverside, Riverside, California, United States of America
| | - Katherine A. Borkovich
- Department of Plant Pathology and Microbiology, Institute for Integrative Genome Biology, University of California Riverside, Riverside, California, United States of America
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