The effect of nitrogen nutrition on the lysine content and protein composition of barley seeds

Abstract

Increases in the total grain nitrogen of barley (cv. Julia and Bomi), resulting from increased N fertilisation, are accompanied by decreases in the relative lysine content of the grain proteins. Extraction of the grain proteins shows that the high-N grain have increased relative and total amounts of the lysine-poor storage protein (hordein) fraction. There are only small increases in the total amounts of the other more lysine-rich protein fractions (salt-soluble proteins and glutelint residue proteins).There is also little or no effect on the amino acid compositions of the fractions.Consequently, it is concluded that the decreased relative lysine content of the whole grain is due to the increased synthesis of hordein. Further evidence for this hypothesis comes from similar studies with the high-lysine mutant, Riser 1508, in which the high-lysine character results from a decrease in the relative and total amount of hordein. The hordein fraction does not increase disproportionately with increasing grain N, nor does the relative lysine content of the grain decrease. There is no effect of grain N on the polypeptide compositions of the salt-soluble proteins of either line. However, in Bomi and Julia increased grain N does result in an increase in the relative amount of sulphur-poor 'C' hordein polypeptides in the hordein fraction. I t is speculated that this results from limitation of S relative to N.

Improved extraction of prolamins for gluten detection in processed foods

“…In seeds, the relative proportion of prolamins increases when the total protein content increases (Kirkman et al 1982). If the prolamin content of the sample is high, a more efficient extraction protocol is needed than for the sample with low prolamin content.…”

Hordein and Malting Quality in Northern Barleys

“…The low grain N yield of Maltine, in turn, seemed to be connected with good malting quality. KIRKMAN et al (1982) indicated that, although increases in N nutrition led to increased N accumulation in the seed, N was distributed among the protein groups in markedly different ways according to variety. These points indicate that even if malting quality of barley tends to decrease due to more efficient N uptake, some cultivars deviate positively from this trend by having high grain N concentration, but low grain N yield which does not increase the D:B ratio, and thus leads to good quality malt.…”

“…These points indicate that even if malting quality of barley tends to decrease due to more efficient N uptake, some cultivars deviate positively from this trend by having high grain N concentration, but low grain N yield which does not increase the D:B ratio, and thus leads to good quality malt. It has been shown ( KIRKMAN et al 1982) that under growing conditions of high N availability but limited availability of sulphur, increased grain protein results in an increased proportion of extractable C hordein polypeptides. In this study a significant increase in the concentration of D hordein in GLY-SDS-ME extraction was observed (r = 0.77) when grain N yield (kg ha-') of the 19 barley cultivars increased in two separate experiments where sulphur was not a limiting factor.…”

Developments in plant breeding for improved nutritional quality of soya beans I. Protein and amino acid content

“…(Helms & Orf 1998). In barley, high N nutrition resulted in a greater protein concentration in the seed and a differential accumulation of seed storage protein types (Kirkman et al 1982), although the net effect was a reduction in protein quality (Guise & Hopp 1984). (Figure 1 about here) In soya bean lines from a single cross, ranging in protein concentration from 370-500g/kg, methionine and protein concentration showed a minimal negative correlation (Burton et al 1982).…”