Cellular concentrations and uniformity of cell-type accumulation of two Lea proteins in cotton embryos.
1993
Roberts J.K. | DeSimone N.A. | Lingle W.L. | Dure L. III.
The levels and cell-type distribution of late embryogenesis abundant (Lea) proteins D-7 and D-113 have been determined in mature cotton embryos by immunochemical methods. The two proteins were expressed in and purified from Escherichia coli and utilized for antibody production in rabbits. The antiserum to each protein was found to interact with all members of each protein family in cotton extracts by protein gel blotting. Using these antibodies in quantitative "rocket" immunoelectrophoreses, D-7 proteins were found to accumulate to approximately 8 X 10(15) molecules per embryo, which is equivalent to approximately 10(9) molecules per "average cell." D-113 proteins accumulate to approximately 10(16) molecules per embryo, which equates to approximately 1.3 X 10(9) molecules per average cell. These values calculate to concentrations of about 226 and 283 micromolar, respectively, in the cell aqueous phase immediately prior to seed desiccation. In immunocytochemical studies using the fluorophor rhodamine linked to the secondary antibody, both proteins appeared to be evenly present in the cytosol of all cell types present in the embryo, including both cotyledon and axis epidermal cells. Thus, their function does not appear related to unique functions of specific cell or tissue types. The very high molar concentrations of the two proteins, coupled with their unusual predicted structure and their cytosol location, would seem to reduce the number of their conceivable functions.
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