Differential gene expression during stationary phase between amicronucleates and micronucleates of the ciliated protist, Pseudourostyla cristata.

Ciliates are unicellular eukaryotic organisms with two types of nuclei, the 'germline' micronucleus (MIC) and the 'somatic' macronucleus (MAC). We previously reported that when the MIC of Pseudourostyla cristata was eliminated by amputation, the resultant amicronucleate organisms exhibited a lower viability and abnormal oral structures. To gain insight into the genetic reorganization involved in or induced by removal of the MIC and the mechanism by which nuclear dimorphism was established, we investigated gene expression differences between amicronucleates and micronucleates, using suppression subtractive hybridization (SSH) techniques. Approximately 250 clones from each library were screened by cDNA array dot blotting. Altogether, 22 unique genes from the forward-subtractive library (micronucleates as tester, amicronucleates as driver) and 23 unique genes from the reverse-subtractive library (micronucleates as driver and amicronucleates as tester) were shown to be differentially expressed. These 45 differentially expressed genes were found to be homologs of genes involved in various cellular processes including signal transduction, transcription, cell cycle accomplishment and general metabolism, cell structure, and stress response. We highlighted 14 genes, 7 that were unique from both the forward-subtractive and the reverse-subtractive libraries, using real time semi-quantitative RT-PCR. The characterization of these cDNAs represents a starting point in understanding the molecular mechanisms of amicronucleates disruption.