A "CELL-CONTACT TEMPERATURE-SENSITIVE" MUTANT OF THE CELLULAR SLIME MOLD DICTYOSTELIUM MUCOROIDES

Area of Science:

• Cell Biology
• Developmental Biology
• Mycology

Background:

• Cellular slime molds, like Dictyostelium mucoroides, are model organisms for studying cell differentiation and morphogenesis.
• Cell-to-cell adhesion is crucial for the coordinated development and aggregation of these organisms.

Purpose of the Study:

• To investigate the role of temperature-sensitive mutations in cell contact during Dictyostelium development.
• To characterize the cellular defects and molecular changes associated with temperature-induced loss of cell adhesion.

Main Methods:

• Isolation and characterization of a temperature-sensitive mutant (TS-2) in Dictyostelium mucoroides.
• Microscopic observation of cell behavior and development at permissive (21°C) and restrictive (31.5°C) temperatures.
• Analysis of cell-cell and cell-substratum contact, aggregation stream dynamics, and cell-wall substance production.

Main Results:

• The TS-2 mutant exhibits normal growth and development at 21°C but fails to grow at 31.5°C.
• Shifting TS-2 to 31.5°C at the aggregation stage causes immediate loss of cell-to-cell contact, leading to aggregation stream disintegration and center flattening.
• At 31.5°C, TS-2 amebas lose cell-to-substratum contact and produce cell-wall substance, a phenomenon also observed in aggregation and migration stages but not vegetative cells.
• Exposure to 31.5°C reduces morphogenetic capacity in proportion to cell-wall substance production upon return to 21°C.

Conclusions:

• Temperature-sensitive defects in cell adhesion significantly disrupt Dictyostelium development.
• Loss of cell contact at elevated temperatures is linked to the production of cell-wall substance in specific developmental stages.
• The study identifies a critical temperature-dependent mechanism regulating cell adhesion and morphogenesis in cellular slime molds.