DEVELOPMENTAL PATTERN OF BIOTINYLATED PROTEINS DURING EMBRYOGENESIS AND MATURATION OF SOYBEAN SEED

The developmental pattern of biotinylated proteins (BP) during embryog enesis and maturation of soybean seed was characterized. Detection of these BP was compared with the development of desiccation tolerance in seeds. Three groups of BP were detected in soybean seeds using a biot in-streptavidin detection method: the first group consisted of a set o f three bands with a mean apparent MW of 85 kDa (called BP85), detecte d in crude extracts of embryonic axes (EA) from non-dehydrated seeds ( NDS) and from artificially slow-dehydrated seeds (DS); the second one, BP75, was a single protein with an apparent MW of 75 kDa and was expr essed in cotyledons (COT) and EA tissues of NDS and DS; the third grou p with a mean apparent MW of 35 kDa (BP35), was expressed at high leve ls only in COT of NDS. BP35 concentration was highest in the early sta ges of seed development (21 days after flowering - DAF) and decreased as seeds developed, being almost imperceptible after 47 DAF. Conversel y, only traces of BP75 and BP85 extracted from EA and COT were detecte d at early stages of seed development (21-33 DAF). Maximum levels of a ccumulation of these proteins were expressed at 42-47 DAF and remained constant until harvest maturity. Desiccation-tolerant stage of the se eds was initiated at 47 DAF, which coincided with the stage of maximum accumulation of BP75 and BP85 in the seeds, however, appearance of th ese proteins could be stimulated by desiccation of immature seeds that had not achieved desiccation tolerance. Therefore changes in biotinyl ated proteins are coincident with, but not sufficient for, the develop ment of desiccation tolerance.