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Title: Manipulation of cyanogenesis and starch biosynthesis in cassava
Keywords: Cassava, cyanogenesis, storage root, starch biosynthesis, genetic variation, gene expression
Issue Date: 28-Sep-2004
Citation: ROY JOSEPH (2004-09-28). Manipulation of cyanogenesis and starch biosynthesis in cassava. ScholarBank@NUS Repository.
Abstract: Studies were carried out to manipulate cyanogenesis and starch biosynthesis in cassava. It was found that the amount of linamarin in roots could be attributed partly to biosynthesis in its own tissues and partly by translocation from leaves. Different mutant lines were raised by I?-irradiation of somatic embryos. Out of 21 lines, none of the mutants showed reduced linamarin content. Mutant lines were also screened for alteration in starch biosynthesis. Line S9 showed very low storage root yield, reduced starch and amylose content, along with distinct variations in starch granule morphology and structure-function properties as compared to wild type plants. Variations in terms of chromosome architecture and nuclear DNA content were not observed in S9 plants. The gross differences in starch pattern were attributed to the low catalytic activity of some of the key enzymes of carbohydrate metabolism (ADP-glucose pyrophosphorylase, granule bound starch synthase and branching enzyme) in storage roots of S9 plants. RT-PCR and gene expression studies confirmed low transcript level for the respective genes of these enzymes in S9 plant storage root tissues. This could account for the low activity of the corresponding enzymes in S9 plants and thereby affecting starch biosynthesis. Two proteins were also found to be absent or weakly present in S9 plant storage roots and were identified as starch phosphorylase and Hsp70 heat shock protein. The results were discussed in relation with carbohydrate metabolism of higher plants. The possibility of using these findings on starch biosynthesis in storage roots of cassava for future crop improvement programmes was also discussed.
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