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Overexpression of CAF1 encoding a novel Ca 2+ ‐binding protein stimulates the transition of Dictyostelium cells from growth to differentiation
Author(s) -
Itoh Mikiko,
Noguchi Maiko,
Maeda Yasuo
Publication year - 1998
Publication title -
development, growth and differentiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.864
H-Index - 66
eISSN - 1440-169X
pISSN - 0012-1592
DOI - 10.1046/j.1440-169x.1998.t01-2-00012.x
Subject(s) - chemistry , gene , microbiology and biotechnology , mutant , dictyostelium , null cell , messenger rna , cellular differentiation , cell growth , biochemistry , biology
Among the expressed genes associated with the switch‐over of Dictyostelium cells from cell proliferation to differentiation, the Calfumirin‐1 ( CAF1 ) gene has been shown to be preferentially expressed at the initial step of differentiation, encoding a novel Ca 2+ ‐binding protein (Abe & Maeda 1995). To analyze precisely the function of CAF1 , transformants overexpressing the CAF1 mRNA at the vegetative growth phase and also CAF1 ‐null mutants were prepared, and their developmental features were compared with those of parental wild‐type cells. As a result, the CAF1 ‐overexpression was found to promote cell differentiation, possibly through prompt induction of the cAMP receptor 1 ( CAR1 ) gene expression. In addition, the CAF1 ‐overexpressing cells were able to differentiate even under low external Ca 2+ ([Ca 2+ ] e ) conditions around 10 −6 mol/L at which non‐transformed wild‐type cells never differentiated. Unexpectedly, however, the CAF1 ‐null mutant produced by homologous recombination exhibited apparently normal development to form fruiting bodies on non‐nutrient agar. These results seem to indicate that CAF1 ‐overexpression has a stimulatory effect on differentiation, but that the CAF1 protein is not necessarily required for the phase‐shift of cells from growth to differentiation.