Babilonia-Figueroa, Kevin

Profile Picture

Filters

20141
Reset filters

Settings

Citations

Publication Search Results

Now showing 1 - 1 of 1
  • Thumbnail Image
    Publication
    Characterization of novel cassava genes involved in cyanide detoxification, β-cyanoalanine synthase and cysteine synthase, using Arabidopsis thaliana mutants
    (2014) Babilonia-Figueroa, Kevin; Siritunga, Dimuth; College of Arts and Sciences - Sciences; Porch, Timothy; Montalvo, Rafael; Department of Biology; Rivera, Aixa
    Cassava (Manihot esculenta crantz) is a perennial shrub of the family Euphorbiaceae and is one of the most important foods in the world. As a subsistence crop, it is highly competitive due to its advantages in production such as high yields per hectare. Cassava can be easily cultivated and is tolerant to extreme stress conditions such as drought. It is propagated very easily as cuttings with up to 20 cuttings being obtained from one plant. Its tuberous roots are rich in starch, being an excellent source of calories for humans. Besides the advantages of cassava, it contains high amounts of cyanogenic glycosides, which are compounds that yield free cyanide. The cyanogenic glycoside of major abundance in cassava is linamarin, which is synthesized from valine in reactions that occur in the vacuole of the plant cell. Linamarin can be hydrolyzed by the cell wall associated linamarase, especially when there is tissue rupture, producing acetone cyanohydrin. Therefore, poorly processed cassava roots will accumulates toxic levels of acetone cyanohydrin, which can cause cyanide associated health problems such as Konzo, Tropical Ataxic Neuropathy and Goitre. Despite the fact that cassava has a cyanide detoxification pathway, it is not enough for the removal of all the cyanide in some varieties. Recently, two genes from the cassava detoxification pathway, MANes;BsasA and MANes;BsasB, where isolated and based on enzyme assays MANes;BsasB may be involved directly in the cyanide detoxification pathway and MANes;BsasA in cysteine biosynthesis, which is also important in the cyanide detoxification pathway. Prior to utilizing these novel genes for genetic transformation of cassava they have been studied using mutants of the model plant Arabidopsis thaliana. Mutants have target genes in the cyanide detoxification pathway silenced thus enabling the functional complementation with the novel cassava genes. Two different expression vectors (pKYLX and pB2GW7) were used in this study for the transformation of the plants with Agrobacterium tumefaciens. The floral dipping method was performed using many modifications since false positive transgenics were obtained in multiple experiments. However, the selection protocol employed was unable to confirm transgenic lines with the T-DNA integrated into its genome. It is believed that the concentration of the surfactant Silwet L-77 that was used for the transformation protocol could have interfered with the transformation mechanism. The plant stage can also be a factor for the lack of transgenic plants due to the importance of the right flowering stage in the floral dipping method. It is also possible that a mutation in any of the virulence genes from Agrobacterium resulted in no T-DNA transfer due to the importance of the virulence genes in this process. Furthermore, mutations or gene rearrangements in areas like the selectable marker or its promoter, or the T-DNA borders, could also affect the integration of the T-DNA into the plant genome. Detailed sequencing of the T-DNA region could be employed to verify that there are no mutations.