Hordein Gene Expression in a Low Protein Barley Cultivar

The low protein barley (Hordeum vulgare L.) cultivar ;Karl' is deficient in hordeins, the major storage protein fraction, but has normal levels of other endosperm protein fractions. We compared hordein gene expression in Karl with that in ;Traill,' a related cultivar that contains normal amounts of hordein. In plants grown in controlled environmental conditions, hordein accumulation in Karl was 55% of that in Traill. The amount of hordein synthesized at all developmental stages tested was lower in Karl, as shown by pulse labeling of excised spikes with [(3)H]leucine. To determine whether levels of hordein mRNAs were related to amounts of hordein synthesis, total RNA preparations from endosperms at three or four developmental stages were hybridized to cDNA probes corresponding to B and C hordein genes. Both B and C hordein mRNA levels were significantly lower in Karl than in Traill at intermediate developmental stages. It was concluded that the low-hordein character of Karl was regulated by the size of the hordein mRNA pool. Transcriptional and/or post-transcriptional controls may be involved in the regulation of hordein mRNA levels.