Abstract

Quinoa (Chenopodium quinoa) is an Andean crop adapted to harsh environmental conditions and containing a high and well-balanced protein composition. Two seed storage proteins, the 2S albumin and 11S globulin, are the major amino acid reservoirs for the developing seedling. An in-depth study of the genes encoding these proteins is necessary to understand the source of quinoa's protein quality. Our objectives include identification and sequencing of the 11S genomic and cDNA clones, analysis of 11S expression profiles in different quinoa accessions and evaluation of evolutionary relationships between the sequence of the 11S gene in quinoa and homologous genes in other species. Clones containing 11S cDNA and genomic DNA were identified and sequenced. Two copies of the gene were found to be present at two different loci in the quinoa genome. The amino acid composition of the 11S gene was also analyzed. Results show that the 11S gene contains a well-balanced assortment of essential amino acids with relatively high levels of glutamate/glutamine, aspartate/asparagine, arginine, serine, leucine and glycine, typical of other 11S seed storage proteins. Total RNA and globulin was extracted from seed collected at different developmental intervals from nine quinoa accessions. Expression profiles were determined by evaluating 11S transcript levels using relative quantification real time RT-PCR and comparing relative 11S globulin accumulation using sodium SDS-PAGE. The 11S gene was found to be expressed during late-maturation regardless of differences in maturation rate. A portion of the amino acid sequence of the 11S and homologous genes was chosen for phylogenetic analysis. Fifty five such sequences from 50 different plant species were assembled and aligned. Two phylogenetic reconstructions, one using the parsimony method and the other using Bayesian analysis, were generated in order to analyze evolutionary relationships between the 11S gene in quinoa and homologous genes in other species. Relationships shown by both reconstructions for sequences from closely-related species were consistent with taxonomic clustering. Both reconstructions showed less resolution involving relationships between distantly-related angiosperm taxa indicating a wide divergence of sequence at the angiosperm level and a need for additional angiosperm sequence data for finer resolution.

Degree

MS

College and Department

Life Sciences; Plant and Wildlife Sciences

Rights

http://lib.byu.edu/about/copyright/

Date Submitted

2006-07-20

Document Type

Thesis

Handle

http://hdl.lib.byu.edu/1877/etd1494

Keywords

quinoa, 11S, legumin, BAC

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