Gene expression in the soybean seed axis during germination and early seedling growth

Abstract

Copy-DNA clones have been obtained that distinguish eight messenger mRNAs, moderately abundant in the axes of the germinating soybean (Glycine max (L.) Merr.) seedling. These clones have been used to characterize the size of the mRNAs and to anlyze the accumulation of the mRNAs at different time points and in different parts of the axis during germination and early seedling growth. Three of the mRNAs accumulate to a substantial level by 9 h, a time point before either the beginning of growth or the accumulation of polyribosomes. Four other mRNAs reach a substantial level only at 24 h, a period when rapid seedling growth is occurring. Those mRNAs whose accumulation begins at 24 h were found only in the top (hypocotyl) half of the 24-h seedlings, while the remaining mRNAs were present also in the bottom half of the seedlings in different amounts. By 44 h, the bottom 0.5 cm of the seedlings, i.e., the region of meristematic growth, had little or none of the mRNAs, with the exception of one mRNA. These temporal and spatial observations indicate that many of the mRNAs are not involved simply in the general maintenance of ongoing cell proliferation, but that they may be related to differentiation during early seedling formation. Further, the early accumulating mRNAs may be functioning in regulating the onset of seedling growth.

Characterization of two soybean repetitive proline-rich proteins and a cognate cDNA from germinated axes.

“…Probes 1 and 3 were labeled by nick translation and probe 2 by phosphorylating the 5' end with 7-32 P-ATP. Hybridization was done as described (Datta et al, 1987), except that probe 2 was used without heat-denaturing. With probe 1, the blots were washed twice at room temperature for 15 min in 0.5 x SSC and twice at 50°C for 30 min in 0.2 x SSC.…”

“…Seedlings of 3.5 cm to 4.5 cm in length were transferred to a box where they were maintained upright with the roots immersed in tap water (Datta et al, 1987). After 6 hr in the light, the seedlings were kept on a continuous 24-hr regime of 8 hr darkness and 16 hr light.…”

“…The concentration of poly(A) RNA was determined according to Rosbash and Ford (1974). Electrophoresis of RNA and the hybridization of RNA gel blot transfers were done as previously described (Datta et al, 1987). The washing conditions for the different probes are given in the legend to Figure 5.…”

“…Selection of hybridizing colonies, growth of selected transformants, and the preparation of the 364-nucleotide 1Al0-1 probe have been previously described (Datta et al, 1987;AveryhartFullard, Datta, and Marcus, 1988). Sequencing of double-stranded plasmids was done with Sequenase following the instructions of the manufacturer (U.S. Biochemicals Corp.).…”

The Roles of Germin Gene Products in Plants Under Salt Stress

“…The gene for phytochrome is also stimulated in expression in germinated pea axes (Konomi et al, 1987). The amount of phytochrome mRNA and that of the mRNA for glutamine synthetase (glutamate-ammonia lyase EC 6.3.1.2) (clone 2A2; Datta et al, 1987), peaks shortly after the onset of increased embryo fresh weight, suggesting that these mRNAs can be regarded as functioning primarily in the maintenance of steady-state growth. Glutamine synthetase gene expression is also abundant in soybean seedling root tips (where the predominant activity is cell division and early elongation) and in rapidly growing soybean cell cultures (very little or no differentiation occurs), a conclusion again consistent with the notion that this gene is particularly involved in growth-maintenance, presumably through its role in nitrogen assimilation.…”