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  • 1.
    Karim, Sazzad
    et al.
    University of Skövde, School of Life Sciences.
    Lundh, Dan
    University of Skövde, School of Humanities and Informatics.
    Holmström, Kjell-Ove
    University of Skövde, School of Life Sciences.
    Mandal, Abul
    University of Skövde, School of Life Sciences.
    Pirhonen, Minna
    Department of Applied Biology, University of Helsinki, Box 27, 00014 Helsinki, Finland.
    Structural and functional characterization of atPTR3, a stress-induced peptide transporter of Arabidopsis2005In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 11, no 3, p. 226-236Article in journal (Refereed)
    Abstract [en]

    A T-DNA tagged mutant line of Arabidopsis thaliana, produced with a promoter trap vector carrying a promoterless gus (uidA) as a reporter gene, showed GUS induction in response to mechanical wounding. Cloning of the chromosomal DNA flanking the T-DNA revealed that the insert had caused a knockout mutation in a PTR-type peptide transporter gene named At5g46050 in GenBank, here renamed AtPTR3. The gene and the deduced protein were characterized by molecular modelling and bioinformatics. Molecular modelling of the protein with fold recognition identified 12 transmembrane spanning regions and a large loop between the sixth and seventh helices. The structure of AtPTR3 resembled the other PTR-type transporters of plants and transporters in the major facilitator superfamily. Computer analysis of the AtPTR3 promoter suggested its expression in roots, leaves and seeds, complex hormonal regulation and induction by abiotic and biotic stresses. The computer-based hypotheses were tested experimentally by exposing the mutant plants to amino acids and several stress treatments. The AtPTR3 gene was induced by the amino acids histidine, leucine and phenylalanine in cotyledons and lower leaves, whereas a strong induction was obtained in the whole plant upon exposure to salt. Furthermore, the germination frequency of the mutant line was reduced on salt-containing media, suggesting that the AtPTR3 protein is involved in stress tolerance in seeds during germination.

  • 2.
    Levefelt, Christer
    et al.
    University of Skövde, School of Humanities and Informatics.
    Lundh, Dan
    University of Skövde, School of Humanities and Informatics.
    A fold-recognition approach to loop modeling2006In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 12, no 2, p. 125-139Article in journal (Refereed)
    Abstract [en]

    A novel approach is proposed for modeling loop regions in proteins. In this approach, a prerequisite sequence-structure alignment is examined for regions where the target sequence is not covered by the structural template. These regions, extended with a number of residues from adjacent stem regions, are submitted to fold recognition. The alignments produced by fold recognition are integrated into the initial alignment to create an alignment between the target sequence and several structures, where gaps in the main structural template are covered by local structural templates. This one-to-many (1:N) alignment is used to create a protein model by existing protein-modeling techniques. Several alternative approaches were evaluated using a set of ten proteins. One approach was selected and evaluated using another set of 31 proteins. The most promising result was for gap regions not located at the C-terminus or N-terminus of a protein, where the method produced an average RMSD 12% lower than the loop modeling provided with the program MODELLER. This improvement is shown to be statistically significant.

  • 3.
    Nahar, Noor
    et al.
    University of Skövde, School of Bioscience. University of Skövde, The Systems Biology Research Centre.
    Rahman, Aminur
    University of Skövde, School of Bioscience. University of Skövde, The Systems Biology Research Centre.
    Moś, Maria
    Department of Plant Breeding and Seed Science, University of Agriculture in Krakow, Krakow, Poland.
    Warzecha, Tomasz
    Department of Plant Breeding and Seed Science, University of Agriculture in Krakow, Krakow, Poland.
    Ghosh, Sibdas
    School of Arts and Science, Iona College, New Rochelle, USA.
    Hossain, Khaled
    Department of Biochemistry and Molecular Biology, University of Rajshahi, Bangladesh.
    Nawani, Neelu N.
    Dr. D. Y. Patil Biotechnology and Bioinformatics Institute, Dr. D. Y. Patil Vidyapeeth University, Tathawade, Pune 411033, India.
    Mandal, Abul
    University of Skövde, School of Bioscience. University of Skövde, The Systems Biology Research Centre.
    In silico and in vivo studies of molecular structures and mechanisms of AtPCS1 protein involved in binding arsenite and/or cadmium in plant cells2014In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 20, no 3, article id 2104Article in journal (Refereed)
    Abstract [en]

    This paper reports a continuation of our previous research on the phytochelatin synthase1 (PCS1) gene involved in binding and sequestration of heavy metals or metalloids in plant cells. Construction of a 3D structure of the Arabidopsis thaliana PCS1 protein and prediction of gene function by employing iterative implementation of the threading assembly refinement (I-TASSER) revealed that PC ligands (3GC-gamma-glutamylcysteine) and Gln50, Pro53, Ala54, Tyr55, Cys56, Ile102, Gly161, His162, Phe163, Asp204 and Arg211 residues are essential for formation of chelating complex with cadmium (Cd²⁺) or arsenite (AsIII). This finding suggests that the PCS1 protein might be involved in the production of the enzyme phytochelatin synthase, which might in turn bind, localize, store or sequester heavy metals in plant cells. For validation of the in silico results, we included a T-DNA tagged mutant of Arabidopsis thaliana, SAIL_650_C12, (mutation in AtPCS1 gene) in our investigation. Furthermore, using reverse transcriptase PCR we confirmed that the mutant does not express the AtPCS1 gene. Mutant plants of SAIL_650_C12 were exposed to various amounts of cadmium (Cd²⁺) and arsenite (AsIII) and the accumulation of these toxic metals in the plant cells was quantified spectrophotometrically. The levels of Cd²⁺ and AsIII accumulation in the mutant were approximately 2.8 and 1.6 times higher, respectively, than that observed in the wild-type controlled plants. We confirmed that the results obtained in in silico analyses complement those obtained in in vivo experiments.

  • 4.
    Nahar, Noor
    et al.
    University of Skövde, The Systems Biology Research Centre. University of Skövde, School of Life Sciences.
    Rahman, Aminur
    University of Skövde, The Systems Biology Research Centre. University of Skövde, School of Life Sciences.
    Mós, Maria
    University of Agriculture in Krakow.
    Warzecha, Tomasz
    University of Agriculture in Krakow.
    Algerin, Maria
    University of Skövde, The Systems Biology Research Centre. University of Skövde, School of Life Sciences.
    Ghosh, Sibdas
    Dominican University of California.
    Johnson-Brousseau, Sheila
    Dominican University of California.
    Mandal, Abul
    University of Skövde, The Systems Biology Research Centre. University of Skövde, School of Life Sciences.
    In silico and in vivo studies of an Arabidopsis thaliana gene, ACR2, putatively involved in arsenic accumulation in plants2012In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 18, no 9, p. 4249-4262Article in journal (Refereed)
    Abstract [en]

    Previously, our in silico analyses identified four candidate genes that might be involved in uptake and/or accumulation of arsenics in plants: arsenate reductase 2 (ACR2), phytochelatin synthase 1 (PCS1) and two multi-drug resistant proteins (MRP1 and MRP2) [Lund et al. (2010) J Biol Syst 18:223–224]. We also postulated that one of these four genes, ACR2, seems to play a central role in this process. To investigate further, we have constructed a 3D structure of the Arabidopsis thaliana ACR2 protein using the iterative implementation of the threading assembly refinement (I-TASSER) server. These analyses revealed that, for catalytic metabolism of arsenate, the arsenate binding-loop (AB-loop) and residues Phe-53, Phe-54, Cys-134, Cys-136, Cys-141, Cys-145, and Lys-135 are essential for reducing arsenate to arsenic intermediates (arsenylated enzyme-substrate intermediates) and arsenite in plants. Thus, functional predictions suggest that the ACR2 protein is involved in the conversion of arsenate to arsenite in plant cells. To validate the in silico results, we exposed a transfer-DNA (T-DNA)-tagged mutant of A. thaliana (mutation in the ACR2 gene) to various amounts of arsenic. Reverse transcriptase PCR revealed that the mutant exhibits significantly reduced expression of the ACR2 gene. Spectrophotometric analyses revealed that the amount of accumulated arsenic compounds in this mutant was approximately six times higher than that observed in control plants. The results obtained from in silico analyses are in complete agreement with those obtained in laboratory experiments.

  • 5.
    Svensson, Maria
    et al.
    University of Skövde, School of Life Sciences.
    Lundh, Dan
    University of Skövde, School of Humanities and Informatics.
    Ejdebäck, Mikael
    University of Skövde, The Systems Biology Research Centre. University of Skövde, School of Life Sciences.
    Mandal, Abul
    University of Skövde, School of Life Sciences.
    Functional prediction of a T-DNA tagged gene of Arabidopsis thalianaby in silico analysis2004In: Journal of Molecular Modeling, ISSN 1610-2940, E-ISSN 0948-5023, Vol. 10, no 2, p. 130-138Article in journal (Refereed)
    Abstract [en]

    We have employed a gene-knockout approach using T-DNA tagging and in vivo gene fusion in Arabidopsis thaliana for identification and isolation of specific plant genes. Screening of about 3,000 T-DNA tagged lines resulted in identification of a mutant line (no. 197) exhibiting a significant delay in flowering. From this line a 600-bp plant DNA fragment downstream of the left T-DNA junction was cloned by inverse PCR. BLAST searching in the A. thaliana genomic database indicated a putative gene, frf (flowering regulating factor), with unknown function downstream of the T-DNA insert. Bioinformatic tools were used to predict possible protein structure and function. The protein structure predicted by fold recognition indicates that frf is a transcriptional regulator, a ligand-binding receptor responsive to steroids and hormones. Analyzing the predicted results and the phenotype of the T-DNA tagged plant we hypothesized that FRF might be involved in hormone response in A. thaliana. For verification of this hypothesis we exposed the plants of line no. 197 to gibberellic acid (GA3), a potential growth regulator in higher plants. This treatment resulted in an earlier onset of flowering, almost similar to that in wild type control plants.

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