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Abstract
Light has been shown to affect aggregation and founder cell development in the cellular slime mould Polysphondylium violaceum. An aggregation-stimulating factor, D factor, also affects aggregation of P. violaceum wild-type and aggregation-defective mutants in the complementation group aggA. Both light and D factor cause premature aggregation of amoebae and increase the number of aggregate centres formed. In addition, D factor is able to stimulate aggregation of wild-type amoebae at densities where aggregation would not normally occur. Several experiments show that amoebae are more sensitive to D factor in the presence of light, with optimum aggregation occurring in the presence of both light and D factor. Development of founder cells has been observed in the aggA mutants in the absence of D factor. However, these founder cells are inactive and do not produce aggregates until D factor is added. This class of inactive founder cells can be detected in wild-type amoebae. Production of D factor is also dependent on light with a 20- to 60-fold decrease in production over that occurring in darkness. A complex relationship between D factor, light and founder cell differentiation is established by this study.
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