Metabolism of acetate-2-14C, glycine-2-14C, leucine-U-14C, and effect of δ-aminolevulinic acid on chlorophyll synthesis in Gateway barley and its mutant

Abstract

Studies with acetate-2-14C showed that leaves of light-grown seedlings of the mutant were less efficient in the synthesis of protein particularly at the 6-day stage. The synthesis of leucine from labeled acetate was also lower in the mutant at this stage. Metabolism of leucine-U-14C confirmed the lower rate of protein synthesis in light by the mutant at the 6-day stage whereas, in the dark, protein synthesis in the two lines was similar. There was essentially no difference in the use of labeled glycine by the two lines. Free and protein amino acids accounted for over 75% of the label. Glycine was rapidly converted to serine, which contained over 65% of the label in the free amino acid fraction but less than 50% of the label in the protein fraction. Evidence for the existence of two separate pools of serine was obtained. Only 3 to 5% of the label from glycine was detected in chlorophyll.Administration of δ-aminolevulinic acid increased chlorophyll synthesis in the mutant in the same proportion as it did in the normal. It was, therefore, concluded that inadequate production of δ-aminolevulinic acid or its precursors was not responsible for the virescent character of the mutant. Rather it seems that the mutation caused a partial inhibition of synthesis of chlorophyll holochrome protein which accounted for the slower accumulation of chlorophyll in the mutant.