The objective of these studies was to determine the step at which dietary selenium (Se) regulates the pre-translational expression of the gene for cytosolic Se-glutathione peroxidase (Se-GPX) in rat liver. Weanling male Sprague-Dawley rats were fed a Torula yeast-based Se-deficient diet, or the same diet supplemented with 0.5 mg/kg as Na2SeO3, for at least 40 d. Livers were excised and divided into three portions for isolation of nuclei, for purification of total RNA and for assay of Se-GPX activity. Nuclei were used in run-on transcription assays and for isolation of total nuclear RNA. Nuclear RNA and total liver RNA were probed with segments from a rat Se-GPX cDNA in Northern blot and slot blot assays. Despite marked differences in Se-GPX activity, there were no significant differences between dietary groups in the transcription rates of the Se-GPX gene. Species hybridizing to Se-GPX were not detected in nuclear RNA. However, steady state levels of Se-GPX mRNA were markedly reduced by Se deficiency. These results suggest that dietary Se exerts its effect on pretranslational Se-GPX gene expression at the level of cytosolic mRNA stabilization.

Quinoa {Chenopodium quinoa Willd) is an important domesticated food crop of the Andean highlands with potential as an alternative crop elsewhere. Among Its most attractive characteristics are the quantity and favorable amino acid balance of the seed proteins. The objective of this study was to characterize quinoa seed proteins by electrophoretic mobility, solubility fractionation, and genetic variability from a wide genetic base. Electrophoretic profiles of denatured albumin, globulin, prolamin, and glutelin solubility fractions demonstrated that quinoa seed polypeptides could be classified as either albumin or globuhn with most predominant polypeptides in the globulin fraction. Insignificant amounts of protein were present in the prolamin fraction and all polypeptides in the glutelin fraction had identical electrophoretic mobilities to albumins and globulins. Three globulin polypeptides of 34.3, 35.6, and 36.2 kilodaltons in size were highly variable within and among the accessions examined and appear to be coded by at least two loci. Twodimensional peptide mapping revealed that these three polypeptides were homologous. These highly variable markers could be used for identification and classification of germplasm and elucidation of systematics and genetic variability within the quinoa germplasm pool. All other major polypeptides were electrophoretically invariant among the accessions examined.

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