Protein Synthesis in Embryos of Dormant and Germinating Agrostemma githago L. seeds

Abstract

ABSTRACIThe time course of protein synthesis in embryos of dormant and afterripened Agrostemma githago seeds was studied. In embryos of afterripened geminating seeds, protein synthesis increased in three successive stages: (a) concurrent with swelling; (b) during the lag phase between the completion of water uptake and the onset of growth; and (c) immediately after protrusion through the seed coat. Embryos of dormant seeds showed the first increase but not the second unless dormancy was broken by imbibition at 4°C. This indicates that dormancy affects processes prior to the onset of growth. The third increase was largely due to higher oxygen availability after the rupture of the seed coat and not to actual growth. It could also be elicited in dormant embryos by isolating them from the seeds.Electrophoretic analysis of the newly synthesized proteins demonstrated that the patterns of dormant and afterripened embryos became significantly different in both axes and cotyledons only just prior to the onset of axis elongation. Thereafter, the differences became larger.When afterripened or dormant seeds were transferred from a low, germination-permitting to a high, germination-inhibiting temperature, the seeds germinated at the high temperature if they had completed the lag phase to a sufficient extent at the low temperature. This shows that the processes during the lag phase were inhibited by the high temperature while the onset of growth was not affected.The germination process of nondormant seeds can be divided into three successive phases: (a) the uptake of water; (b) a lag period during which processes seem to take place in preparation for growth; and (c) axis elongation together with a rupture of the seed coat (21,28 (9,19,20). In contrast, in light-requiring and in hormone-stimulated seeds the rate ofprotein synthesis exceeds that of untreated, D seeds after the induction but before the onset of growth (16,24,27,30). In all these studies, however, the actual differences in protein synthesis might have been obscured by differential dilution of applied precursors by the en- ' [3H]leucine and 10 mM unlabeled leucine were added. Since the embryos were isolated from the seeds just prior to labeling, this is considered to represent the course of protein synthesis in embryos of intact seeds. In one experiment, imbibition and incubation were carried out at 4°C. The incubation time was then 1 h. In another experiment, various concentrations of unlabeled leucine were added instead of 10 mM.To determine the time course of protein synthesis in isolated embryos, embryos were excised from seeds 6 h after the start of imbibition, preincubated for increasing periods in 10 mM KCI, 1 mm CaC12, and 50 MAg ml-' chloramphenicol after which they were incubated for 30 min in 38 kBq [3H]leucine and 10 mM unlabeled leucine. This will be referred to as the course ofprotein synthesis in isolated embryos.For electrophoretic analysis, samples of 10 embryos were isolated from seeds after various periods of imbibition at 20°C and incubated...

Assembly of Agrostemma githago (corn-cockle) storage proteins and their precursor proteins into oligomers

“…This study supplements our investigations on protein synthesis in relation to dormancy and germination of Agrostemma githago seeds (de Klerk, 1983;de Klerk & Smulders, 1984). Previously we reported that Agrostemma storage proteins are synthesized through post-translational cleavage of large precursor polypeptides (de Klerk, 1984a).…”

A comparison of the synthesis of DNA, RNA and proteins in the embryos of after-ripened and thermo- or FR-dormantAgrostemma githagoL. seeds

“…3a). In axes of primarily dormant Agrostemma seeds protein synthesis is arrested after 6 h of imbibition (De Klerk, 1983). During the time when depression of protein synthesis occurs in embryos of after-ripened seeds RNA synthesis is intensified.…”

Nutritional Profiles of Yoom Noon Rice from Royal Initiative of Southern Thailand: A Comparison of White Rice, Brown Rice, and Germinated Brown Rice

“…The increase in protein content caused by germination could be attributed to the production of some proteins, peptides, and amino acids during renewed protein biosynthesis. Protein synthesis is thought to have increased in three stages: (a) concomitant with swelling; (b) during the lag phase between the end of water intake and the start of development; (c) shortly following protrusion through the seed coat [28]. The additional source of nitrogen that serves as a precursor for protein synthesis may come from the air and water that the seed may absorb during soaking and germination.…”