To prevent oxidative damage by • O2 2 , cells have several forms of the enzyme superoxide dismutase, which catalyzes the formation of hydrogen peroxide (H2O2)

TLS Online TPP Program

#Id: 7424

#Unit 5. Developmental Biology

Dictyostelium can utilize one of three survival strategies when food starvation-

 Microcyst formation, favoured in dark & wet conditions, or ammonia levels are high.

 Zygote formation, favoured in dark & wet conditions, & is triggered by ethylene produced by the cells. 

Cell aggregation & differentiation

TLS Online TPP Program

#Id: 7425

#Unit 5. Developmental Biology

Cell Aggregation & Differentiation is common to all Dictyostelids. It consists of an interconnected programme of cell movement and cell differentiation.

TLS Online TPP Program

#Id: 7426

#Unit 5. Developmental Biology

During growth, unicellular D. discoideum monitor their cell density relative to that of their bacterial food source by secreting a glycoprotein called prestarvation factor at a constant rate.

TLS Online TPP Program

#Id: 7427

#Unit 5. Developmental Biology

When the ratio of PSF relative to that of bacteria exceeds a certain threshold, cells stop proliferating and initiate the expression of genes that are required for their aggregation.

TLS Online TPP Program

#Id: 7428

#Unit 5. Developmental Biology

Early on during aggregation, gene expression requires the activity of cAMP-dependent protein kinase.

TLS Online TPP Program

#Id: 7429

#Unit 5. Developmental Biology

High PSF to food ratio is upregulate the translation of the PKA catalytic subunit PKA-C.