DNA, RNA, protein and heterochromatin changes during embryo development and germination of soybean (Glycine max L.)

Abstract

DNA, RNA, protein and heterochromatin were measured cytophotometrically in developing soybean (Glycine max) seeds. The average 2C DNA content for the soybean genome was 2.64 pg. The amounts of nuclear DNA in embryo axes showed no significant change during embryo development, whereas the DNA content in cotyledon nuclei increased significantly from 3.58 pg to 5.49 pg. The number of endopolyploid nuclei increased from 26% to 48% and the DNA content from 4.45 to 5.49 pg after cessation of cell division. The changes in RNA and protein content during embryo development were in general similar to those in DNA content. This can be interpreted that increased DNA levels in soybean cotyledons generated during embryogeny increase the protein synthesizing capacity. During the first 15 days of germination, the number of endopolyploid nuclei in cotyledons declined from 46% to 4%, and this decline is interpreted as DNA degradation providing a ready source of nucleosides and phosphates during early embryo growth. A later decline, however, between 15 and 20 days after germination, was age related similar to leaf senescence, because the percentage of endopolyploid nuclei remained unchanged while the number of non-viable cells increased. In senescing cotyledons, 73% and 80% of RNA and protein but only 20% of DNA were lost, as compared to dormant cotyledons. The heterochromatin (condensed chromatin) measurements indicated that nuclei of metabolically inactive dormant and senescent cotyledon nuclei contained an average of 33% more heterochromatin than nuclei from the green cotyledons of seedlings.

Using Genomics to Study Legume Seed Development

“…some of the earliest measurements of RNA, DNA, carbohydrates, lipids, and protein levels in seeds (Rubel et al, 1972;Clutter et al, 1974;Hill and Breidenbach, 1974;Davies, 1976;Pattee et al, 1981;Singh et al, 1981;Adams et al, 1982;Dhillon and Miksche, 1983). These studies provided new insights into the processes by which food reserves accumulate and are stored in seeds, as well as demonstrating that genome endoreduplication processes occur in specific seed compartments (e.g.…”

DNA and RNA Levels in Bundle Sheath and Mesophyll Cells of Pearl Millett (Pennisetum americanum)

“…1C) and mesophyll cell nuclei, and the distributions of relative DNA contents of the two cell types are shown in Figure 2 Although several possibilities can be offered to explain the higher DNA content of mesophyll cells, we are not yet able to determine which accounts for the differences reported here. Among the possibilities are polyploidization, differential cell cycle arrest, selective chromosome duplication or DNA amplification, and/ or selective loss of DNA or chromosomes (8,12,13,15). In many plant species, DNA endoreduplication is an important feature of cell development (1), although it is not considered essential for tissue or organ differentiation in all higher plants (15).…”

“…No polyploid cells were found in any tissue of Helianthus annuus examined, but polyploidy in Pisum sativum tissues was the rule, rather than the exception. Likewise, cells in the cotyledons of developing soybean seedlings differed significantly in DNA content depending on the age of the tissue sampled (13). These results indicate that individual cells within a single tissue may differ in nuclear DNA content, as may tissues within a single organ.…”

Nuclear Size and DNA Content of the Embryo and Endosperm During their Initial Stages of Development in Glycine max (Fabaceae)

“…These latter results are similar to those noted in G. max cv. Dare (Dhillon and Miksche, 1983). They observed 50/o-7% of the cotyledon nuclei above the 4C level and a mean DNA content of 2.7C at 15 days postanthesis through the "very early maturation" stage.…”

“…Supplying nutrients necessary for growth of the embryo is a typical function of the endosperm of angiosperms. The loss of DNA may form a pool of free bases possibly serving as a ready source of deoxynucleosides and phosphates for the developing embryo (Dhillon and Miksche, 1983). Further research is necessary to determine the exact nature and consequence of DNA loss in this tissue.…”