Fig, 2. 



phosphatase. This would tend to aid the accumu- 

 lation of UDPG by removing pyrophosphate. 

 Neither of these enzymes changes strikingly 

 during development, but UDPG synthetase does 

 increase about threefold at culmination. 



A number of precursors of cell wall ma- 

 terial increase and then decrease prior to 

 sorocarp construction. Figure 4 shows data 

 obtained by Mr. Beers in our laboratory on 

 glucose-6-phosphate accumulation in a number 

 of stage studies. As you can see, there is a good 

 deal of variation from one stage to another, but 

 in general, glucose-6-phosphate reaches a peak 

 at culmination. 



Figure 5 is a schematic summary of the 

 accumulation pattern of a number of poly- 

 saccharide precursors and of some end products 

 of differentiation. Gluscose, glucose-6-phos- 

 phate, glucose- 1 -phosphate and UDPG increase 

 and decrease in the cells during development 

 as cellulose, mucopolysaccharides, trehalose 

 and an alpha-1, 4 polymer, which I will discuss, 

 accumulate. Since cell wall construction occurs 

 only at the terminal stages of development, it 

 represents an excellent index of differentiation. 

 We wanted to know exactly what conditions in 

 the starving, differentiating cells set the stage 

 for cell wall accumulation. This work was done 

 in collaboration with Carole Ward and Donna 

 Dahlberg. 



CELL WALL 



UDPG + PP- 

 4^ 



GIP + UTP 



-T^P 



^GLUCOSE 



KREBS CYCLE 



CULM SORO 



Fig. 4, 



From Wright, Barbara E.: Control of Carbohydrate 

 Synthesis in the Slime Mold. In Developmental and Meta- 

 bolic Control Mechanisms and Neoplasia (A Collection of 

 Papers Presented at the Nineteenth Annual Symposium 

 on Fundamental Cancer Research, 1965), p. 301. Balti- 

 more, The Williams and Wllkins Company, 1965. 



In order to study cell wall synthesis in 

 vitro, husk preparations of culminating or ter- 

 minal stage cells were made by passing the 

 cells through a French pressure cell and then 

 washing extensively in tris-EDTA buffer. These 

 cells were then incubated with radioactive UDPG, 



111 



