Enzyme Activity Changes during Cyclic AMP-induced Stalk Cell Differentiation in p4, a Variant of Dictyostelium discoideum

Abstract

S U M M A R YThe ~4 variant of Dictyostelium discoideum is characterized by the production of fruiting structures in which the overall proportion of stalk to spore material is increased, relative to the wild type. The altered morphology of the mutant is due to increased sensitivity to cyclic AMP which promotes stalk cell differentiation. In the presence of I O -~ M-cyclic AMP the entire population of ~4 amoebae forms clumps of stalk cells on the surface of the dialysis membrane support.Measurement of changes in activity of a range of developmentally-regulated enzymes during the development of ~4 in the presence and absence of cyclic AMP has allowed us to identify three classes of enzyme : (i) Those, such as /3-glucosidase 11, trehalose-6-phosphate synthetase and uridine diphosphogalactose-4-epimerase, which are required for the production of spores. (ii) Enzymes, primarily but perhaps not exclusively, required during stalk cell formation, Typical of these are N-acetylglucosaminidase and alkaline phosphatase. (iii) General enzymes, such as threonine dehydrase, a-mannosidase and uridine diphosphoglucose pyrophosphorylase, which are present in both pre-stalk and pre-spore cells and appear to be necessary for the development of both cell types. I N T R O D U C T I O NChanges in enzyme specific activities during the development of the cellular slime moulds have been studied to understand the biochemical mechanisms underlying development. Sussman and his co-workers (for a review, see Sussman & Sussman, 1969) have focused their attention on the role of transcription and translation of enzymes while Wright (1966, 1972) and her associates look to the role of enzyme substrates and products in the chemical control of development. As has been pointed out (Francis, 1969;Bonner, 1971; Newell, 197r), there is no conflict between these two proposed mechanisms and it is reasonable to assume that both play a role in development.Development leads to the production of both stalk cells and spores and these exhibit different metabolic activities during development. By dissection of individual slugs, Newell, Ellingson & Sussman (I 969) demonstrated that different programmes of enzyme synthesis occurred during the development of stalk cells and spores. This approach is however limited to that period in development when pre-stalk and pre-spore cells are separable in the aggregate, and does not allow either to be examined throughout development. Since a separation of spore cell development from stalk cell development is possible in the variant ~4 , we have used it in our studies. In the development of ~4 there is both stalk cell and spore differentiation, .but in the development of ~4 amoebae with 1 0 -4 M-

Protein synthesis during development and differentiation in the cellular slime mould Dictyostelium discoideum

“…Cyclic AMP and control of protein synthesis during development Identification of cyclic AMP as the chemoattractant controlling aggregation of D. discoideum amoebae stimulated further investigations to determine whether this nucleotide might also control other aspects of development, and it is now generally believed that a high cyclic AMP concentration is essential for both spore and stalk cell differentiation (Bonner, 1970;Hamilton & Chia, 1975;Town et al, 1976;Coukell & Chan, 1980;Gross et al, 1981;Kay, 1982). First attempts to determine whether cyclic AMP had any effects on protein synthesis were concentrated particularly on cyclic AMP phosphodiesterase and contact sites A, which were known to appear in amoebae during early development when adenylate cyclase becomes active in catalysing synthesis of the cyclic AMP needed to induce cell aggregation.…”

Cellular Communication during Aggregation of Dictyostelium: The Second Fleming Lecture: (Delivered at the General Meeting of the Society for General Microbiology on 8 September 1977)

“…(From Newell, 1978; reproduced with perniission of The National Foundation, March of Dimes.) differentiate directly into stalk cells (Bonner, 1970;Chia, 1975;Hamilton & Chia, 1975;Town, Gross & Kay, 1976). The concentrations necessary for this phenomenon are high ( 1 0 0 , u~ to 1 mM) but this may be due to inefficient transport into the amoebae from outside (compared with that between touching amoebae) and to the presence of the phosphodiesterase enzymes.…”