Differential gene expression during the amoebal-plasmodial transition in Physarum

Area of Science:

• Molecular Biology
• Developmental Biology
• Mycology

Background:

• The acellular slime mould, Physarum polycephalum, exists in two distinct life stages: a unicellular amoebal stage and a multicellular plasmodial stage.
• Understanding the molecular mechanisms underlying the transition between these stages is crucial for comprehending cellular differentiation and development.

Purpose of the Study:

• To investigate the transcriptional changes occurring during the developmental transition of Physarum polycephalum from amoebae to plasmodia.
• To identify cell-type-specific genes involved in this developmental switch.

Main Methods:

• Construction of complementary DNA (cDNA) libraries from both amoebal and plasmodial stages of Physarum polycephalum.
• Differential screening of cDNA libraries to isolate cell-type-specific clones.
• Analysis of transcriptional changes using Southern blotting to assess gene copy number and genomic organization.

Main Results:

• Approximately 5% of isolated cDNA sequences were specific to either the amoebal or plasmodial stage.
• The transition from amoebal to plasmodial characteristics is associated with significant changes in gene transcription.
• These transcriptional changes occur gradually over several nuclear division cycles.
• Specific cDNAs predominantly originated from single-gene families.
• Southern blotting indicated that the genes encoding these specific cDNAs are present in identical restriction fragments in both amoebal and plasmodial DNA, suggesting no major genomic rearrangements are involved.

Conclusions:

• The developmental transition in Physarum polycephalum is regulated primarily by changes in gene expression rather than alterations in genome structure.
• The observed transcriptional modifications suggest a complex regulatory process occurring over multiple cell cycles during the amoebal-plasmodial differentiation.