Hormonal Control of Mitotic Development in Tobacco Protoplasts

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Abstract
Two-dimensional separation of proteins newly synthesized by tobacco mesophyll protoplasts cultivated in vitro allows us to detect, reproducibly, 257 spots. The pattern is extremely stable throughout the three days of culture, the intensity of only 24 spots varying during this time. The absence of cytokinin (N6-benzyladenine) in the culture medium prohibits entry into S phase but does not modify the pattern, indicating that none of the observed proteins is specifically synthesized in S, G2, or M phases. The presence of 2,4-dichlorophenoxyacetic acid is necessary for the mitotic development of protoplasts. It induces the appearance of one protein, increases the level of another, and reduces that of eight others. All proteins sensitive to auxin belong to the group of proteins the levels of which vary during culture.