NOVEL INVENTION OF SPORE INDUCTION IN A SISTER SPECIES TO GROUP 4 DICTYOSTELIA.

Area of Science:

• Cellular and Molecular Biology
• Developmental Biology
• Microbiology

Background:

• Dictyostelia are soil amoebas that aggregate and form fruiting bodies under starvation.
• cAMP signaling is typically essential for dictyostelid spore differentiation and fruiting body construction.
• Polyspondylium violaceum (Pvio) exhibits intact sporulation despite lacking a functional cAMP receptor (cAR).

Purpose of the Study:

• To investigate Pvio sporulation in the absence of secreted cAMP.
• To identify alternative signaling molecules that induce sporulation in Pvio.
• To explore the genetic mechanisms underlying Pvio development.

Main Methods:

• Identified and characterized three Pvio prespore genes (psp1, psp2, psp3) as homologs of Dictyostelium discoideum (Ddis) spore coat genes.
• Created gene fusions of prespore gene promoters with the LacZ reporter gene for Pvio transformation.
• Assessed spatial and temporal prespore gene expression patterns and the effects of various signaling molecules (cAMP, Pvio glorin, Ddis chemoattractants) in vitro and on solid substratum.

Main Results:

• Prespore genes psp1, psp2, and psp3 were expressed in aggregation centers and later in developing fruiting bodies.
• Prespore gene expression increased significantly when Pvio cells were plated on solid substratum for development.
• Neither cAMP nor other tested signaling molecules (glorin, folate, c-di-GMP, DIF-1, GABA, cGMP, 8Br-cAMP) induced prespore gene expression in Pvio.

Conclusions:

• P. violaceum utilizes a novel genetic network for sporulation, independent of canonical cAMP signaling.
• This finding highlights a unique evolutionary adaptation in Pvio for survival and development.
• Dictyostelid signaling pathways for development are more diverse than previously understood.