scholarly journals Phenotypic Heterogeneity of the Insect Pathogen Photorhabdus luminescens: Insights into the Fate of Secondary Cells

2019 ◽  
Vol 85 (22) ◽  
Author(s):  
Simone Eckstein ◽  
Nazzareno Dominelli ◽  
Andreas Brachmann ◽  
Ralf Heermann
Keyword(s):  
Plant Root ◽  
Phenotypic Switching ◽  
Transcriptional Level ◽  
Photorhabdus Luminescens ◽  
Way Of Life ◽  
Content Type ◽  
Nutrient Sources ◽  
Phenotypic Differences ◽  
Successful Infection ◽  
As Stress

ABSTRACT Photorhabdus luminescens is a Gram-negative bacterium that lives in symbiosis with soil nematodes and is simultaneously highly pathogenic toward insects. The bacteria exist in two phenotypically different forms, designated primary (1°) and secondary (2°) cells. Yet unknown environmental stimuli as well as global stress conditions induce phenotypic switching of up to 50% of 1° cells to 2° cells. An important difference between the two phenotypic forms is that 2° cells are unable to live in symbiosis with nematodes and are therefore believed to remain in the soil after a successful infection cycle. In this work, we performed a transcriptomic analysis to highlight and better understand the role of 2° cells and their putative ability to adapt to living in soil. We could confirm that the major phenotypic differences between the two cell forms are mediated at the transcriptional level as the corresponding genes were downregulated in 2° cells. Furthermore, 2° cells seem to be adapted to another environment as we found several differentially expressed genes involved in the cells’ metabolism, motility, and chemotaxis as well as stress resistance, which are either up- or downregulated in 2° cells. As 2° cells, in contrast to 1° cells, chemotactically responded to different attractants, including plant root exudates, there is evidence for the rhizosphere being an alternative environment for the 2° cells. Since P. luminescens is biotechnologically used as a bio-insecticide, investigation of a putative interaction of 2° cells with plants is also of great interest for agriculture. IMPORTANCE The biological function and the fate of P. luminescens 2° cells were unclear. Here, we performed comparative transcriptomics of P. luminescens 1° and 2° cultures and found several genes, not only those coding for known phenotypic differences of the two cell forms, that are up- or downregulated in 2° cells compared to levels in 1° cells. Our results suggest that when 1° cells convert to 2° cells, they drastically change their way of life. Thus, 2° cells could easily adapt to an alternative environment such as the rhizosphere and live freely, independent of a host, putatively utilizing plant-derived compounds as nutrient sources. Since 2° cells are not able to reassociate with the nematodes, an alternative lifestyle in the rhizosphere would be conceivable.

scholarly journals The Biocontrol Agent and Insect Pathogen Photorhabdus luminescens Interacts with Plant Roots

2020 ◽  
Vol 86 (17) ◽  
Author(s):  
Alice Regaiolo ◽  
Nazzareno Dominelli ◽  
Karsten Andresen ◽  
Ralf Heermann
Keyword(s):  
Biological Control ◽  
Pest Management ◽  
Root Exudates ◽  
Biological Control Agent ◽  
Plant Root ◽  
Specific Interaction ◽  
Plant Roots ◽  
Photorhabdus Luminescens ◽  
Content Type ◽  
Root Interactions

ABSTRACT The number of sustainable agriculture techniques to improve pest management and environmental safety is rising, as biological control agents are used to enhance disease resistance and abiotic stress tolerance in crops. Here, we investigated the capacity of the Photorhabdus luminescens secondary variant to react to plant root exudates and their behavior toward microorganisms in the rhizosphere. P. luminescens is known to live in symbiosis with entomopathogenic nematodes (EPNs) and to be highly pathogenic toward insects. The P. luminescens-EPN relationship has been widely studied, and this combination has been used as a biological control agent; however, not much attention has been paid to the putative lifestyle of P. luminescens in the rhizosphere. We performed transcriptome analysis to show how P. luminescens responds to plant root exudates. The analysis highlighted genes involved in chitin degradation, biofilm regulation, formation of flagella, and type VI secretion system. Furthermore, we provide evidence that P. luminescens can inhibit growth of phytopathogenic fungi. Finally, we demonstrated a specific interaction of P. luminescens with plant roots. Understanding the role and the function of this bacterium in the rhizosphere might accelerate the progress in biocontrol manipulation and elucidate the peculiar mechanisms adopted by plant growth-promoting rhizobacteria in plant root interactions. IMPORTANCE Insect-pathogenic Photorhabdus luminescens bacteria are widely used in biocontrol strategies against pests. Very little is known about the life of these bacteria in the rhizosphere. Here, we show that P. luminescens can specifically react to and interact with plant roots. Understanding the adaptation of P. luminescens in the rhizosphere is highly important for the biotechnological application of entomopathogenic bacteria and could improve future sustainable pest management in agriculture.

scholarly journals Differential Locus Expansion Distinguishes Toxoplasmatinae Species and Closely Related Strains of Toxoplasma gondii

mBio ◽  
2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Yaw Adomako-Ankomah ◽  
Gregory M. Wier ◽  
Adair L. Borges ◽  
Hannah E. Wand ◽  
Jon P. Boyle
Keyword(s):  
Toxoplasma Gondii ◽  
Gene Duplication ◽  
Copy Number ◽  
Neospora Caninum ◽  
Comparative Genomic ◽  
Transcriptional Level ◽  
World Population ◽  
Content Type ◽  
Phenotypic Differences ◽  
Species Specific

ABSTRACT Toxoplasma gondii is a human obligate intracellular parasite that has infected over 20% of the world population and has a vast intermediate host range compared to those of its nearest relatives Neospora caninum and Hammondia hammondi. While these 3 species have highly syntenic genomes (80 to 99%), in this study we examined and compared species-specific structural variations, specifically at loci that have undergone local (i.e., tandem) duplication and expansion. To do so, we used genomic sequence coverage analysis to identify and curate T. gondii and N. caninum loci that have undergone duplication and expansion (expanded loci [ELs]). The 53 T. gondii ELs are significantly enriched for genes with predicted signal sequences and single-exon genes and genes that are developmentally regulated at the transcriptional level. We validated 24 T. gondii ELs using comparative genomic hybridization; these data suggested significant copy number variation at these loci. High-molecular-weight Southern blotting for 3 T. gondii ELs revealed that copy number varies across T. gondii lineages and also between members of the same clonal lineage. Using similar methods, we identified 64 N. caninum ELs which were significantly enriched genes belonging to the SAG-related surface (SRS) antigen family. Moreover, there is significantly less overlap (30%) between the expanded gene sets in T. gondii and N. caninum than would be predicted by overall genomic synteny (81%). Consistent with this finding, only 59% of queried T. gondii ELs are similarly duplicated/expanded in H. hammondi despite over 99% genomic synteny between these species. IMPORTANCE Gene duplication, expansion, and diversification are a basis for phenotypic differences both within and between species. This study represents the first characterization of both the extent and degree of overlap in gene duplication and locus expansion across multiple apicomplexan parasite species. The most important finding of this study is that the locus duplications/expansions are quantitatively and qualitatively distinct, despite the high degree of genetic relatedness between the species. Given that these differential expansions are prominent species-specific genetic differences, they may also contribute to some of the more striking phenotypic differences between these species. More broadly, this work is important in providing further support for the idea that postspeciation selection events may have a dramatic impact on locus structure and copy number that overshadows selection on single-copy genes.

Tissue tolerance mechanisms conferring salinity tolerance in a halophytic perennial species Nitraria sibirica Pall.

2020 ◽  
Author(s):  
Xiaoqian Tang ◽  
Huilong Zhang ◽  
Sergey Shabala ◽  
Huanyong Li ◽  
Xiuyan Yang ◽  
...  
Keyword(s):  
Plant Root ◽  
Transcriptional Level ◽  
Distribution Analysis ◽  
Specific Level ◽  
Saline Environment ◽  
Nitraria Sibirica ◽  
Mechanistic Basis ◽  
Plant Salt Tolerance ◽  
Cellular Compartments ◽  
Growth Of Seedlings

Abstract Plant salt tolerance relies on a coordinated functioning of different tissues and organs. Salinity tissue tolerance is one of the key traits that confers plant adaptation to saline environment. This trait implies maintenance low cytosolic Na+/K+ ratio in metabolically active cellular compartments. In this study, we used Nitraria sibirica Pall., a perennial woody halophytes species, to understand the mechanistic basis of its salinity tissue tolerance. The results showed that the growth of seedlings was stimulated by 100-200 mM NaCl treatment. The ions distribution analysis showed that the leaves acted as Na+ sink while plant root possess superior K+ retention. The excessive Na+ absorbed from soil was mainly transported to the shoot and eventually sequestrated into mesophyll vacuoles in the leaves. As a result, N. sibirica could keep optimal balance of K+/Na+ at a tissue- and cell-specific level under saline condition. To enable this, N. sibirica increased both vacuolar H+-ATPase and H+-PPase enzymes activities and up-regulated expressions of NsVHA, NsVP1 and NsNHX1 genes. Vacuolar Na+ sequestration in the leaf mesophyll mediated by NsVHA, NsVP1 and NsNHX1 reduced the Na+ concentration in cytosol and inhibited further K+ loss. Meanwhile, N.sibirica enhanced the TPK expression at the transcriptional level to promote K+ efflux from vacuole into cytoplasm, assisting in maintaining cytosolic K+ homeostasis. It is concluded that the tissue tolerance traits such as vacuolar Na+ sequestration and intracellular K+ homeostasis is critical to confer adaptation of N. sibirica to soil salinity.

Litorilinea aerophila gen. nov., sp. nov., an aerobic member of the class Caldilineae , phylum Chloroflexi , isolated from an intertidal hot spring

2013 ◽  
Vol 63 (Pt_3) ◽  
pp. 1149-1154 ◽  
Author(s):  
Varsha Kale ◽  
Snædís H. Björnsdóttir ◽  
Ólafur H. Friðjónsson ◽  
Sólveig K. Pétursdóttir ◽  
Sesselja Ómarsdóttir ◽  
...  
Keyword(s):  
Type Species ◽  
Hot Spring ◽  
Sequence Similarity ◽  
Rrna Gene ◽  
Content Type ◽  
Phenotypic Differences ◽  
Link Type ◽  
Fermentative Growth ◽  
Distinct Lineage ◽  
Ph Range

A thermophilic, aerobic, Gram-stain-negative, filamentous bacterium, strain PRI-4131T, was isolated from an intertidal hot spring in Isafjardardjup, NW Iceland. The strain grew chemo-organotrophically on various carbohydrates. The temperature range for growth was 40–65 °C (optimum 55 °C), the pH range was pH 6.5–9.0 (optimum pH 7.0) and the NaCl range was 0–3 % (w/v) (optimum 0.5 %). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain PRI-4131T represented a distinct lineage within the class Caldilineae of the phylum Chloroflexi. The highest levels of sequence similarity, about 91 %, were with Caldilinea aerophila STL-6-O1T and Caldilinea tarbellica D1-25-10-4T. Fermentative growth was not observed for strain PRI-4131T, which, in addition to other characteristics, distinguished it from the two Caldilinea species. Owing to both phylogenetic and phenotypic differences from the described members of the class Caldilineae , we propose to accommodate strain PRI-4131T in a novel species in a new genus, Litorilinea aerophila gen. nov., sp. nov. The type strain of Litorilinea aerophila is PRI-4131T ( = DSM 25763T  = ATCC BAA-2444T).

Flavobacterium akiainvivens sp. nov., from decaying wood of Wikstroemia oahuensis, Hawai‘i, and emended description of the genus Flavobacterium

2013 ◽  
Vol 63 (Pt_9) ◽  
pp. 3280-3286 ◽  
Author(s):  
Iris Kuo ◽  
Jimmy Saw ◽  
Durrell D. Kapan ◽  
Stephanie Christensen ◽  
Kenneth Y. Kaneshiro ◽  
...  
Keyword(s):  
Type Species ◽  
Original Description ◽  
Gliding Motility ◽  
Rrna Gene ◽  
Content Type ◽  
Phenotypic Differences ◽  
Whole Cells ◽  
Link Type ◽  
Decaying Wood ◽  
Type Strains

Strain IK-1T was isolated from decaying tissues of the shrub Wikstroemia oahuensis collected on O‘ahu, Hawai‘i. Cells were rods that stained Gram-negative. Gliding motility was not observed. The strain was oxidase-negative and catalase-positive. Zeaxanthin was the major carotenoid. Flexirubin-type pigments were not detected. The most abundant fatty acids in whole cells of IK-1T grown on R2A were iso-C15 : 0 and one or both of C16 : 1ω7c and C16 : 1ω6c. Based on comparisons of the nucleotide sequence of the 16S rRNA gene, the closest neighbouring type strains were Flavobacterium rivuli WB 3.3-2T and Flavobacterium subsaxonicum WB 4.1-42T, with which IK-1T shares 93.84 and 93.67 % identity, respectively. The G+C content of the genomic DNA was 44.2 mol%. On the basis of distance from its nearest phylogenetic neighbours and phenotypic differences, the species Flavobacterium akiainvivens sp. nov. is proposed to accommodate strain IK-1T ( = ATCC BAA-2412T = CIP 110358T) as the type strain. The description of the genus Flavobacterium is emended to reflect the DNA G+C contents of Flavobacterium akiainvivens IK-1T and other species of the genus Flavobacterium described since the original description of the genus.

scholarly journals Bacterial Secretions of Nonpathogenic Escherichia coli Elicit Inflammatory Pathways: a Closer Investigation of Interkingdom Signaling

mBio ◽  
2015 ◽  
Vol 6 (2) ◽  
Author(s):  
Amin Zargar ◽  
David N. Quan ◽  
Karen K. Carter ◽  
Min Guo ◽  
Herman O. Sintim ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Epithelial Cells ◽  
Negative Feedback ◽  
Cell Contact ◽  
Bacterial Cells ◽  
Content Type ◽  
Phenotypic Differences ◽  
E Coli ◽  
Autoinducer 2 ◽  
Human Epithelial Cells

ABSTRACTThere have been many studies on the relationship between nonpathogenic bacteria and human epithelial cells; however, the bidirectional effects of the secretomes (secreted substances in which there is no direct bacterium-cell contact) have yet to be fully investigated. In this study, we use a transwell model to explore the transcriptomic effects of bacterial secretions from two different nonpathogenicEscherichia colistrains on the human colonic cell line HCT-8 using next-generation transcriptome sequencing (RNA-Seq).E. coliBL21 and W3110, while genetically very similar (99.1% homology), exhibit key phenotypic differences, including differences in their production of macromolecular structures (e.g., flagella and lipopolysaccharide) and in their secretion of metabolic byproducts (e.g., acetate) and signaling molecules (e.g., quorum-sensing autoinducer 2 [AI-2]). After analysis of differential epithelial responses to the respective secretomes, this study shows for the first time that a nonpathogenic bacterial secretome activates the NF-κB-mediated cytokine-cytokine receptor pathways while also upregulating negative-feedback components, including the NOD-like signaling pathway. Because of AI-2's relevance as a bacterium-bacterium signaling molecule and the differences in its secretion rates between these strains, we investigated its role in HCT-8 cells. We found that the expression of the inflammatory cytokine interleukin 8 (IL-8) responded to AI-2 with a pattern of rapid upregulation before subsequent downregulation after 24 h. Collectively, these data demonstrate that secreted products from nonpathogenic bacteria stimulate the transcription of immune-related biological pathways, followed by the upregulation of negative-feedback elements that may serve to temper the inflammatory response.IMPORTANCEThe symbiotic relationship between the microbiome and the host is important in the maintenance of human health. There is a growing need to further understand the nature of these relationships to aid in the development of homeostatic probiotics and also in the design of novel antimicrobial therapeutics. To our knowledge, this is the first global-transcriptome study of bacteria cocultured with human epithelial cells in a model to determine the transcriptional effects of epithelial cells in which epithelial and bacterial cells are allowed to “communicate” with each other only through diffusible small molecules and proteins. By beginning to demarcate the direct and indirect effects of bacteria on the gastrointestinal (GI) tract, two-way interkingdom communication can potentially be mediated between host and microbe.

Macau’s legal identity

2016 ◽  
Vol 5 (3) ◽  
pp. 342-354
Author(s):  
Jean A. Berlie
Keyword(s):  
Legal Framework ◽  
Chinese Society ◽  
Way Of Life ◽  
Matrix Formulation ◽  
Content Type ◽  
Basic Law ◽  
Legal Identity ◽  
Unique Identity ◽  
Historical Fact ◽  
Definition Of

Purpose – The Macau Special Administrative Region (MSAR) of the People’s Republic of China (PRC) has a unique identity. This study is based on a long period of research undertaken between 1995 and 2014. Permanent residents, the Chinese of Macau and all other MSAR residents constitute a body of model “citizens” which makes their legal identity understandable in the MSAR’s present social and economic context. Macau’s legal identity is based on centuries of trade and commerce. In Article 5 of the first chapter (I-5) of the MSAR’s Basic Law, the “way of life” in Macau’s society and economy are recognized as part of the MSAR’s legal framework. However, social change may play an important role in Macau’s development. The purpose of this paper is to look at the legal corpus as though it was a physical body with rights and duties, but also capabilities based on the nationality and residence statuses of its citizens, its companies and other entities (which will be studied more specifically in following articles). Design/methodology/approach – This study has used the combined approaches of fieldwork carried out between 2010 and 2015, interviews, and questionnaires. Findings – Way of life and the concept of One Country, Two Systems are key points that contribute to Macau’s contemporary identity. Way of life in the Basic Law constitutes a complex matrix formulation based on a series of particular facts and cultural traits, which leads to a better legal definition of important concepts such as nationality and residency in the particular case of Macau. The Basic Law is the constitutional law of the MSAR, but “Chineseness” still dominates the locals’ identity from day to day. More than 65 percent of the interviewees in the survey asserted their “Chineseness.” However, both Chinese and Portuguese, will continue to be official languages of Macau until 2049. The MSAR’s Chinese society speaks Cantonese and increasingly Putonghua, but it does not seem concerned by communicating using the Portuguese language. Clayton’s thesis emphasized the “unique cultural identity” of the MSAR and wrote that what made the Chinese of Macau “different from other Chinese, is the existence of a Portuguese state on Chinese soil.” Portuguese cultural tolerance is not mentioned, but it is a historical fact that has influenced Macau’s legal identity. The MSAR’s government has done its best to harmonize Macau’s multicultural society and it has particularly protected the Sino-Portuguese way of life in Macau. Practical implications – To apply the law and maintain the existing harmony in its society and economy, legal actions have had to be taken by the Macau government and courts. The courts of the MSAR are structured in three levels and have final powers of adjudication, except in very narrow political areas. The judicial system includes the following courts, from the highest to the lowest: the Court of Final Appeal, the Court of Second Instance and the Court of First Instance (Tribunal de Primeira Instância). Originality/value – This research is unique inasmuch as studies of legal identities focussed on large regions such as the MSAR of China are rare.

scholarly journals Plasmodium falciparum Line-Dependent Association ofIn VitroGrowth-Inhibitory Activity and Risk of Malaria

2012 ◽  
Vol 80 (5) ◽  
pp. 1900-1908 ◽  
Author(s):  
Josea Rono ◽  
Anna Färnert ◽  
Daniel Olsson ◽  
Faith Osier ◽  
Ingegerd Rooth ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Inhibitory Activity ◽  
Content Type ◽  
Phenotypic Differences ◽  
Erythrocyte Invasion ◽  
Growth Inhibitory ◽  
Growth Inhibitory Activity ◽  
Control Study

ABSTRACTPlasmodium falciparum's ability to invade erythrocytes is essential for its survival within the human host. Immune mechanisms that impair this ability are therefore expected to contribute to immunity against the parasite. Plasma of humans who are naturally exposed to malaria has been shown to have growth-inhibitory activity (GIA)in vitro. However, the importance of GIA in relation to protection from malaria has been unclear. In a case-control study nested within a longitudinally followed population in Tanzania, plasma samples collected at baseline from 171 individuals (55 cases and 116 age-matched controls) were assayed for GIA using threeP. falciparumlines (3D7, K1, and W2mef) chosen based on their erythrocyte invasion phenotypes. Distribution of GIA differed between the lines, with most samples inhibiting the growth of 3D7 and K1 and enhancing the growth of W2mef. GIA to 3D7 was associated with a reduced risk of malaria within 40 weeks of follow-up (odds ratio, 0.45; 95% confidence interval [CI], 0.21 to 0.96;P= 0.04), whereas GIA to K1 and W2mef was not. These results show that GIA, as well as its association with protection from malaria, is dependent on theP. falciparumline and can be explained by differences in erythrocyte invasion phenotypes between parasite lines. Our study contributes knowledge on the biological importance of growth inhibition and the potential influence ofP. falciparumerythrocyte invasion phenotypic differences on its relationship to protective immunity against malaria.

scholarly journals Identification and Regulation of a Novel Citrobacter rodentium Gut Colonization Fimbria (Gcf)

2015 ◽  
Vol 197 (8) ◽  
pp. 1478-1491 ◽  
Author(s):  
Gustavo G. Caballero-Flores ◽  
Matthew A. Croxen ◽  
Verónica I. Martínez-Santos ◽  
B. Brett Finlay ◽  
José L. Puente
Keyword(s):  
Escherichia Coli ◽  
Intestinal Epithelium ◽  
Pathogenic Bacteria ◽  
Critical Role ◽  
Growth Conditions ◽  
Citrobacter Rodentium ◽  
Content Type ◽  
Gut Colonization ◽  
Successful Infection

ABSTRACTThe Gram-negative enteric bacteriumCitrobacter rodentiumis a natural mouse pathogen that has been extensively used as a surrogate model for studying the human pathogens enteropathogenic and enterohemorrhagicEscherichia coli. All three pathogens produce similar attaching and effacing (A/E) lesions in the intestinal epithelium. During infection, these bacteria employ surface structures called fimbriae to adhere and colonize the host intestinal epithelium. ForC. rodentium, the roles of only a small number of its genome-carried fimbrial operons have been evaluated. Here, we report the identification of a novelC. rodentiumcolonization factor, calledgutcolonizationfimbria (Gcf), which is encoded by a chaperone-usher fimbrial operon. AgcfAmutant shows a severe colonization defect within the first 10 days of infection. Thegcfpromoter is not active inC. rodentiumunder severalin vitrogrowth conditions; however, it is readily expressed in aC. rodentiumΔhns1mutant lacking the closest ortholog of theEscherichia colihistone-like nucleoid structuring protein (H-NS) but not in mutants with deletion of the other four genes encoding H-NS homologs. H-NS binds to the regulatory region ofgcf, further supporting its direct role as a repressor of thegcfpromoter that starts transcription 158 bp upstream of the start codon of its first open reading frame. Thegcfoperon possesses interesting novel traits that open future opportunities to expand our knowledge of the structure, regulation, and function during infection of these important bacterial structures.IMPORTANCEFimbriae are surface bacterial structures implicated in a variety of biological processes. Some have been shown to play a critical role during host colonization and thus in disease. Pathogenic bacteria possess the genetic information for an assortment of fimbriae, but their function and regulation and the interplay between them have not been studied in detail. This work provides new insights into the function and regulation of a novel fimbria called Gcf that is important for early establishment of a successful infection byC. rodentiumin mice, despite being poorly expressed underin vitrogrowth conditions. This discovery offers an opportunity to better understand the individual role and the regulatory mechanisms controlling the expression of specific fimbrial operons that are critical during infection.

scholarly journals Transcriptional Regulation of the Copper Transporter Mfc1 in Meiotic Cells

2013 ◽  
Vol 12 (4) ◽  
pp. 575-590 ◽  
Author(s):  
Jude Beaudoin ◽  
Raphaël Ioannoni ◽  
Stéphane Mailloux ◽  
Samuel Plante ◽  
Simon Labbé
Keyword(s):  
Transcriptional Activation ◽  
Regulatory Element ◽  
Specific Protein ◽  
Copper Transport ◽  
Site Directed Mutagenesis ◽  
Regulatory Sequence ◽  
Transcriptional Level ◽  
Binding Studies ◽  
Copper Transporter ◽  
Content Type

ABSTRACT Mfc1 is a meiosis-specific protein that mediates copper transport during the meiotic program in Schizosaccharomyces pombe . Although the mfc1 + gene is induced at the transcriptional level in response to copper deprivation, the molecular determinants that are required for its copper starvation-dependent induction are unknown. Promoter deletion and site-directed mutagenesis have allowed identification of a new cis -regulatory element in the promoter region of the mfc1 + gene. This cis -acting regulatory sequence containing the sequence TCGGCG is responsible for transcriptional activation of mfc1 + under low-copper conditions. The TCGGCG sequence contains a CGG triplet known to serve as a binding site for members of the Zn (2) Cys (6) binuclear cluster transcriptional regulator family. In agreement with this fact, one member of this group of regulators, denoted Mca1, was found to be required for maximum induction of mfc1 + gene expression. Analysis of Mca1 cellular distribution during meiosis revealed that it colocalizes with both chromosomes and sister chromatids during early, middle, and late phases of the meiotic program. Cells lacking Mca1 exhibited a meiotic arrest at metaphase I under low-copper conditions. Binding studies revealed that the N-terminal 150-residue segment of Mca1 expressed as a fusion protein in Escherichia coli specifically interacts with the TCGGCG sequence of the mfc1 + promoter. Taken together, these results identify the cis -regulatory TCGGCG sequence and the transcription factor Mca1 as critical components for activation of the meiotic copper transport mfc1 + gene in response to copper starvation.

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