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Opabode J.T.,Obafemi Awolowo University | Oyelakin O.O.,International Institute Of Tropical Agriculture | Oyelakin O.O.,c o Lambourn Ltd | Akinyemiju O.A.,Obafemi Awolowo University | Ingelbrecht I.L.,Ghent University
Journal of Agricultural Science | Year: 2013

Several key genes involved in starch biosynthesis have been identified in cassava. However, while phosphorylation has been recognized as an essential step in starch metabolism in higher plants, the underlying gene(s) in cassava have not been isolated so far. To gain insights into starch phosphorylation in cassava, we produced three genomic clones encoding a fragment of an α-glucan, water dikinase (GWD), the primary enzyme required for starch phosphorylation. Sequence analysis showed that each of the clones contained the nucleotide-binding domain of the C-terminus of plant GWDs. The three genomic gwd clones had 98.8% homology at both nucleotide and amino acid levels and represented two distinct allelic sequences with two amino acid substitutions. The shorter clone, pOYE308-1, was 561 base pairs long and encoded a polypeptide of 106 amino acids with a predicted molecular weight of 180.3kDa. Two putative introns were identified in each of the gwd clones. Phylogenetic analysis of the cassava GWD sequences with other plant GWDs revealed that the cassava GWD belongs to the same group as that of castor bean, potato, tomato and tobacco. These resources add to the current knowledge base of starch metabolism in cassava and expand the molecular tool box for starch modification in this important tropical root crop. Source


Vroh-Bi I.,International Institute Of Tropical Agriculture | Vroh-Bi I.,c o Lambourn Ltd | Anagbogu C.,University of Ibadan | Nnadi S.,International Institute Of Tropical Agriculture | And 2 more authors.
Plant Molecular Biology Reporter | Year: 2011

Unexpected variations can occur during natural and in vitro propagation of bananas (banana and plantain) to generate off-types. The molecular basis of such variations is not well-understood. This study aimed to characterize the functions of genomic regions varying within clones grown naturally or in vitro. Fifty-four simple sequence repeat (SSR) markers and six primer combinations of EcoR I/Msp I-amplified fragment length polymorphism (AFLP) were used to analyze accessions of the AA, BB, AB, AAA, AAB, and ABB groups of Musa, and polymorphic regions were sequenced to characterize candidate genes. One SSR locus with significant similarity to an arcelin gene revealed a deletion in a subculture regenerant. In AFLP analysis, 24 (6.15%) of 390 bands accounted for within-clone variations, with 0.5% and 5.65% occurring in natural and in vitro propagated plants, respectively. Sequence homology searches revealed that most polymorphic regions were related to cytochrome P450, cell-wall biosynthesis, and senescence genes. The importance of these candidate genes is discussed. The plants harboring the variations were field-established to relate molecular variations to phenotypic changes. Sixteen of the sequences registered in Genbank (ET165586 to ET165601) and select PCR primers from this study can be further tested for variations between normal clones and off-types in Musa. © 2010 Springer-Verlag. Source


Oyelakin O.O.,International Institute Of Tropical Agriculture | Oyelakin O.O.,c o Lambourn Ltd | Opabode J.T.,Obafemi Awolowo University | Raji A.A.,International Institute Of Tropical Agriculture | And 3 more authors.
South African Journal of Botany | Year: 2015

The study described a T-DNA vector with a Cassava vein mosaic virus promoter cassette (pCsVMV) and a kanamycin selectable marker gene driven by the 35S Cauliflower mosaic virus promoter with a view to stably express transgenes over repeated cycles of clonal propagation. A β-glucuronidase reporter gene under control of pCsVMV (pCsVMV-GUS) was introduced into the cassava landrace 'Tokunbo' via Agrobacterium-mediated genetic transformation. Transgenic tobacco plants (Nicotiana tabacum SR1) with the same gene construct were also produced. In tobacco, the pCsVMV-GUS was highly expressed in all tissues tested such as leaf, stem, petiole, and roots. In transgenic cassava, the pCsVMV-GUS gene was highly expressed in all tissues and most cell types of in vitro plants including leaf, stem, petiole, and fibrous roots. The pCsVMV-GUS gene was also highly expressed in these tissues as well as in tubers of greenhouse grown cassava. High and stable pCsVMV-GUS gene expression was maintained over 3 cycles of ratooning under greenhouse conditions, thus showing the absence of undesired gene silencing effects after repeated in vitro subculturing and vegetative propagation. From the high constitutive levels of GUS activity observed, the study concluded that the CsVMV promoter cassette was useful for high-level expression in cassava over repeated cycles of clonal propagation. © 2014 SAAB. Source


Opabode J.T.,Obafemi Awolowo University | Oyelakin O.O.,International Institute Of Tropical Agriculture | Oyelakin O.O.,c o Lambourn Ltd | Akinyemiju O.A.,Obafemi Awolowo University | And 2 more authors.
Journal of Plant Sciences | Year: 2011

Cassava (Manihot esculenta) is a major source of starch in tropical and subtropical countries. The genomic organization of the granule-bound starch synthase I (GBSS I) in cassava was examined to increase our knowledge of starch biosynthesis and facilitate the production of modified starches in cassava. Three partial genomic clones were generated and the sequence analysis revealed that they were identical at both nucleotide and amino acid levels. The insert in one of the clones, pOYE303-1 (accession no. HM038439), was 731 nucleotides long and encoded a partial protein of 124 amino acids with predicted molecular weight of 13.65 kDa and calculated 10.01 isoelectric point. HM038439 contained the first conserved domains of GBSS including the KTGG motif responsible for ADP-glucose binding site. Phylogenetic analysis revealed that cassava GBSS I belongs to dicot subgroup and is closely related to GBSS I of potato, sweet potato and buckthorn. In silico identification by nucleotide sequence alignment between genomic and cDNA sequences revealed three putative introns in GBSS I. The longest intron was 121 bp long and was located between nucleotide 595 and 716. The implications of these findings on starch biosynthesis and modification are discussed. © 2011 Academic Journals Inc. Source

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