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Armine Margaryan

Bio: Armine Margaryan is an academic researcher from Yerevan State University. The author has contributed to research in topics: Anoxybacillus & Bacilli. The author has an hindex of 5, co-authored 14 publications receiving 101 citations.

Papers
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Journal ArticleDOI
TL;DR: This study highlights the need to include a comprehensive phylogenetic analysis when drawing inferences from structure-function analyses, as a significant proportion of the functional changes observed for TaALMT1 are most likely the result of alterations in the overall structural integrity of ALMT family proteins rather than modifications of specific sites involved in Al(3+) sensing.
Abstract: Triticum aestivum aluminum-activated malate transporter (TaALMT1) is the founding member of a unique gene family of anion transporters (ALMTs) that mediate the efflux of organic acids. A small sub-group of root-localized ALMTs, including TaALMT1, is physiologically associated with in planta aluminum (Al) resistance. TaALMT1 exhibits significant enhancement of transport activity in response to extracellular Al. In this study, we integrated structure-function analyses of structurally altered TaALMT1 proteins expressed in Xenopus oocytes with phylogenic analyses of the ALMT family. Our aim is to re-examine the role of protein domains in terms of their potential involvement in the Al-dependent enhancement (i.e. Al-responsiveness) of TaALMT1 transport activity, as well as the roles of all its 43 negatively charged amino acid residues. Our results indicate that the N-domain, which is predicted to form the conductive pathway, mediates ion transport even in the absence of the C-domain. However, segments in both domains are involved in Al(3+) sensing. We identified two regions, one at the N-terminus and a hydrophobic region at the C-terminus, that jointly contribute to the Al-response phenotype. Interestingly, the characteristic motif at the N-terminus appears to be specific for Al-responsive ALMTs. Our study highlights the need to include a comprehensive phylogenetic analysis when drawing inferences from structure-function analyses, as a significant proportion of the functional changes observed for TaALMT1 are most likely the result of alterations in the overall structural integrity of ALMT family proteins rather than modifications of specific sites involved in Al(3+) sensing.

48 citations

Journal ArticleDOI
TL;DR: The results are spreading light on the lipase producing bacilli distribution in geothermal springs in Armenia and Nagorno Karabakh and could be prospective source for thermostable lipases and their genes.
Abstract: Among the huge diversity of thermophilic bacteria mainly bacilli have been reported as active thermostable lipase producers. Geothermal springs serve as the main source for isolation of thermostable lipase producing bacilli. Thermostable lipolytic enzymes, functioning in the harsh conditions, have promising applications in processing of organic chemicals, detergent formulation, synthesis of biosurfactants, pharmaceutical processing etc. In order to study the distribution of lipase-producing thermophilic bacilli and their specific lipase protein primary structures, three lipase producers from different genera were isolated from mesothermal (27.5–70 °C) springs distributed on the territory of Armenia and Nagorno Karabakh. Based on phenotypic characteristics and 16S rRNA gene sequencing the isolates were identified as Geobacillus sp., Bacillus licheniformis and Anoxibacillus flavithermus strains. The lipase genes of isolates were sequenced by using initially designed primer sets. Multiple alignments generated from primary structures of the lipase proteins and annotated lipase protein sequences, conserved regions analysis and amino acid composition have illustrated the similarity (98–99%) of the lipases with true lipases (family I) and GDSL esterase family (family II). A conserved sequence block that determines the thermostability has been identified in the multiple alignments of the lipase proteins. The results are spreading light on the lipase producing bacilli distribution in geothermal springs in Armenia and Nagorno Karabakh. Newly isolated bacilli strains could be prospective source for thermostable lipases and their genes.

22 citations

Book ChapterDOI
01 Jan 2018
TL;DR: This chapter contains a review of studies of geobacilli and anoxybacilli from terrestrial geothermal springs worldwide with special emphasis on their distribution and diversity, ecological significance, adaptive mechanisms, enzymes, and biotechnological potential.
Abstract: A large number of thermophilic representatives of the Geobacillus and Anoxybacillus genera have been isolated from geographically distant and physicochemically different environments, including high-, moderate-, and low-temperature habitats However, terrestrial hot springs are the main habitats for Geobacillus and Anoxybacillus species The members of these genera possess a variety of thermo-adaptive features that enable them to thrive at elevated temperatures Due to their ability to withstand harsh environmental conditions, geobacilli and anoxybacilli are a valuable source for provision of thermostable enzymes, such as amylases, lipases, proteases, etc, and other components Thermostable enzymes obtained from thermophilic bacilli have found a plethora of commercial applications due to their sturdiness and toughness in withstanding the heat generated in various biotechnological and industrial processes This chapter contains a review of studies of geobacilli and anoxybacilli from terrestrial geothermal springs worldwide with special emphasis on their distribution and diversity, ecological significance, adaptive mechanisms, enzymes, and biotechnological potential

17 citations

Journal ArticleDOI
TL;DR: Bacilli isolated from high-altitude mineralized geothermal springs located within the territory of Armenia and Nagorno-Karabakh shared less than 91–97% sequence identity with their closest match in GenBank, indicating that Armenian geothermal Springs harbor novel bacilli, at least at the species level.
Abstract: In recent years, scientists have increasingly focused on the microbial diversity of high-altitude hot springs to explore the biotechnological applications of extremophiles. In this regard, a total of 107 thermophilic bacilli were isolated from 9 high-altitude mineralized geothermal springs (of temperatures ranging from 27.5 to 70 °C) located within the territory of Armenia and Nagorno-Karabakh. The isolated bacilli were phylogenetically profiled and studied for their potential to produce extracellular hydrolytic enzymes (protease, amylase, and lipase). The identification of isolates based on 16S rRNA gene sequences revealed their relationship to members of more than 22 distinct species, of 8 different genera, namely Aeribacillus, Anoxybacillus, Bacillus, Brevibacillus, Geobacillus, Parageobacillus, Paenibacillus and Ureibacillus. Bacillus licheniformis, Parageobacillus toebii and Anoxybacillus flavithermus were found to be the most abundant species in the springs that were studied. Some of the isolated bacilli shared less than 91–97% sequence identity with their closest match in GenBank, indicating that Armenian geothermal springs harbor novel bacilli, at least at the species level. 71% of the isolates actively produced at least one or more extracellular proteases, amylases, or lipases. In total, 22 strains (28.6%) were efficient producers of all three types of thermostable enzymes.

13 citations

Journal ArticleDOI
TL;DR: An abundance of Firmicutes, Acidobacteria, and Proteobacteria in different layers of the Akhtala tailing and the presence of a large number of yet-uncultivated species emphasizes the importance of the future exploration of the tailing as an important source of novel bacteria.
Abstract: The impact of the heavy metal contamination and acidity on the bacterial community was studied in samples collected from the Akhtala copper mine tailing using molecular approaches. The bacterial community structure analysis by PCR-DGGE fingerprinting revealed an abundance of Firmicutes, Acidobacteria, and Proteobacteria in different layers of the Akhtala tailing. 454 pyrotag sequence analyses revealed that a significant part of the sequences originated from Proteobacteria (49%) and Bacteroidetes (43%). Bacterial taxa are distributed also in phyla Saccharibacteria (2%), Verrucomicrobia (1.5%), Gammatimonadetes (1%), and some minor additional bacterial groups. The main primary producers in the Akhtala tailing appear to be obligate autotrophic Thiobacillus and Sulfuritalea species. Representatives of Lutibacter and Lysobacter genera are the most abundant acid-tolerant heterotrophs in the studied tailing. The presence of a large number of yet-uncultivated species emphasizes the importance of the future exploration of the tailing as an important source of novel bacteria.

10 citations


Cited by
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Journal ArticleDOI
TL;DR: How the integration of molecular and genetic analyses of crop Al resistance is starting to be exploited for the improvement of crop plants grown on acid soils via both molecular-assisted breeding and biotechnology approaches is examined.
Abstract: Aluminum (Al) toxicity in acid soils is a significant limitation to crop production worldwide, as approximately 50% of the world’s potentially arable soil is acidic. Because acid soils are such an important constraint to agriculture, understanding the mechanisms and genes conferring resistance to Al toxicity has been a focus of intense research interest in the decade since the last article on crop acid soil tolerance was published in this journal. An impressive amount of progress has been made during that time that has greatly increased our understanding of the diversity of Al resistance genes and mechanisms, how resistance gene expression is regulated and triggered by Al and Al-induced signals, and how the proteins encoded by these genes function and are regulated. This review examines the state of our understanding of the physiological, genetic, and molecular bases for crop Al tolerance, looking at the novel Al resistance genes and mechanisms that have been identified over the past ten years. Additionally, it examines how the integration of molecular and genetic analyses of crop Al resistance is starting to be exploited for the improvement of crop plants grown on acid soils via both molecular-assisted breeding and biotechnology approaches.

621 citations

Journal ArticleDOI
TL;DR: One of the major unfortunate consequences of industrialization is soil acidification, and aluminium (Al) is the primary limitation of crop productivity worldwide.

310 citations

Journal ArticleDOI
TL;DR: It is demonstrated that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms.
Abstract: The non-protein amino acid, gamma-aminobutyric acid (GABA) rapidly accumulates in plant tissues in response to biotic and abiotic stress, and regulates plant growth. Until now it was not known whether GABA exerts its effects in plants through the regulation of carbon metabolism or via an unidentified signalling pathway. Here, we demonstrate that anion flux through plant aluminium-activated malate transporter (ALMT) proteins is activated by anions and negatively regulated by GABA. Site-directed mutagenesis of selected amino acids within ALMT proteins abolishes GABA efficacy but does not alter other transport properties. GABA modulation of ALMT activity results in altered root growth and altered root tolerance to alkaline pH, acid pH and aluminium ions. We propose that GABA exerts its multiple physiological effects in plants via ALMT, including the regulation of pollen tube and root growth, and that GABA can finally be considered a legitimate signalling molecule in both the plant and animal kingdoms.

260 citations

Journal ArticleDOI
TL;DR: TFM6 (tomato fruit malate 6), which corresponds to Al-ACTIVATED MALATE TRANSPORTER9 (Sl-ALMT9 in tomato), is the major quantitative trait locus responsible for variation in fruit malates accumulation among tomato genotypes and was selected for during tomato domestication.
Abstract: Deciphering the mechanism of malate accumulation in plants would contribute to a greater understanding of plant chemistry, which has implications for improving flavor quality in crop species and enhancing human health benefits. However, the regulation of malate metabolism is poorly understood in crops such as tomato (Solanum lycopersicum). Here, we integrated a metabolite-based genome-wide association study with linkage mapping and gene functional studies to characterize the genetics of malate accumulation in a global collection of tomato accessions with broad genetic diversity. We report that TFM6 (tomato fruit malate 6), which corresponds to Al-ACTIVATED MALATE TRANSPORTER9 (Sl-ALMT9 in tomato), is the major quantitative trait locus responsible for variation in fruit malate accumulation among tomato genotypes. A 3-bp indel in the promoter region of Sl-ALMT9 was linked to high fruit malate content. Further analysis indicated that this indel disrupts a W-box binding site in the Sl-ALMT9 promoter, which prevents binding of the WRKY transcription repressor Sl-WRKY42, thereby alleviating the repression of Sl-ALMT9 expression and promoting high fruit malate accumulation. Evolutionary analysis revealed that this highly expressed Sl-ALMT9 allele was selected for during tomato domestication. Furthermore, vacuole membrane-localized Sl-ALMT9 increases in abundance following Al treatment, thereby elevating malate transport and enhancing Al resistance.

176 citations

Journal ArticleDOI
TL;DR: An overview of Al resistance genes and their function provides verification that Al induction of gene expression plays a major role in Al resistance in many plant species, and the post-transcriptional and translational regulation ofAl resistance proteins is addressed.
Abstract: As researchers have gained a better understanding in recent years into the physiological, molecular, and genetic basis of how plants deal with aluminum (Al) toxicity in acid soils prevalent in the tropics and sub-tropics, it has become clear that an important component of these responses is the triggering and regulation of cellular pathways and processes by Al. In this review of plant Al signaling, we begin by summarizing the understanding of physiological mechanisms of Al resistance, which first led researchers to realize that Al stress induces gene expression and modifies protein function during the activation of Al resistance responses. Subsequently, an overview of Al resistance genes and their function provides verification that Al induction of gene expression plays a major role in Al resistance in many plant species. More recent research into the mechanistic basis for Al-induced transcriptional activation of resistance genes has led to the identification of several transcription factors as well as cis-elements in the promoters of Al resistance genes that play a role in greater Al-induced gene expression as well as higher constitutive expression of resistance genes in some plant species. Finally, the post-transcriptional and translational regulation of Al resistance proteins is addressed, where recent research has shown that Al can both directly bind to and alter activity of certain organic acid transporters, and also influence Al resistance proteins indirectly, via protein phosphorylation.

138 citations