Regulation of Differentiation in Slime Mold Development

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In the development of cellular slime molds, cells aggregate to form a tissue, in which two types of cells(prestalk and prespore) differentiate in the anterior and the posterior parts. To elucidate mechanisms of the pattern formation, we made the following studies.1.By the use of a vector with the actin-basal promoter provided by J.Williams, we analyzed the cis-acting regulatory regions of prespore-specific gene Dp87 and found 4 positive, prespore-specific and 1 negative, non-prespore-specific and 1 positive, cell-type-non-specific regions regulating its transcription.2.The process of stalk differentiation was found to be divided into 4 different stages. Cyclic AMP was required at the second stage and DIF at the third stage, where an unidentified low molecular weight secretory substance was also required. Cyclic AMP given at the third stage rather inhibited both of prestalk-specific ecmA and ecmB genes to the same extent, while 8-Br-cAMP which activates protein kinase A specifically ind … More uced ecmB expression, suggesting involvement of this enzyme in differential expression of the two genes.3.Relationship between the cell-cycle phase and the pattern formation was investigated by using a transformat constitutively expressingbeta-galactosidase. It was found that cells starved before a particular point (PS) within the G2 phase initiated aggregation, but sorted out to the posterior prespore region of a migrating slug, while those starved after that point lagged behind in aggregation, but sorted out to the anterior prestalk region.4.Changes in intracellular free calcium concentration ([(Ca)^<2+>]) and responsiveness to cAMP stumulation during development were studied, by using cells transformed with apoqequorin cDNA of a jellyfish. Cells exhibited a considerable increase in [(Ca)^<2+>] and acquired responsiveness to cAMP by showing a transient increase in [(Ca)^<2+>], at the time of aggregation. Prestalk cells contained twice as much [(Ca)^<2+>] and showed three times as large a response to cAMP as prespore cells. Less