In maize, while both inflorescences are initially bisexual, female spikelets mature into ears and male spikelets mature into tassels. The molecular basis of this differential development has not been studied although plant growth regulators are known to be involved.
We report here preliminary observations on polypeptide variability associated with the maturation of male and female spikelets. Tassels and ears of different developmental stages (lengths) were labelled with diluted 35S-methionine (5 ul in 200 ul H20) for 2 h at 27 C. One hundred spikelets were dissected from each labelled inflorescence. In the case of older (> 12.0 mm) inflorescences, their developing organs (ovary, silk or stamens etc.) were isolated. The tissues were homogenized separately in buffer containing 200 mM tris-HCl, 5% SDS, 7.5% P-mercaptoethanol, 1 mM PMSF, 10% glycerol at pH 7.5. Radioactive incorporation was determined by scintillation counting of TCA precipitable material. Protein samples were separated by 1D SDS PAGE and 2D IEF-SDS PAGE and fluorography was performed.
No major qualitative differences between tassel and ear or between young and older inflorescences were detected on the 1D fluorograms. While many polypeptides (>150) were resolved by 2D PAGE and fluorography, most were common to all fluorograms. A few unique polypeptides were consistently related to specific samples. At least two polypeptides were associated with maturation. One polypeptide (18 kd, approx. pH 7.0) was associated with developing ovaries and silks but not with male flowers. A second polypeptide (25 kd, approx. pH 5.5) was associated with maturing stamens but not with female flowers. In addition, a few polypeptides, unique to either male or female flowers, appeared and then disappeared as the flowers matured. Whether the few polypeptide differences which were detected are related to the regulation of, or are the result of, differentiation remains for further studies.
V.R. Bommineni, R.I. Greyson, D.B. Walden and B.G. Atkinson
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