Nuclear differentiation for mating types in the ciliate Dileptus anser: a hypothesis

Area of Science:

• Genetics
• Cell Biology
• Protozoology

Background:

• Mating types (MTs) are crucial for sexual reproduction in many ciliates.
• The genetic basis of MT determination in Dileptus anser was previously unknown.

Purpose of the Study:

• To investigate the inheritance and genetic determination of mating types in Dileptus anser.
• To understand the mechanisms underlying MT stability and instability in this species.

Main Methods:

• Crosses were performed between different mating types of Dileptus anser.
• Exconjugant clones were monitored for MT expression and stability over several weeks.
• Observations focused on changes in sexual maturity and MTs within clones.

Main Results:

• Instability in MT expression was observed in young exconjugant clones from specific crosses.
• Cells within a clone synchronously alternated between maturity and immaturity, and/or changed MTs, sometimes repeatedly.
• All three known MTs could be expressed consecutively within unstable clones.
• The mat locus appears to be a compound integral locus, inherited as a whole but capable of specifying multiple MTs.

Conclusions:

• The mat locus in D. anser is likely a compound integral locus, similar to Tetrahymena thermophila.
• Epigenetic mechanisms play a role in controlling which MT is expressed.
• Disturbances in these control mechanisms can lead to unstable MT expression and violations of Mendelian inheritance patterns.