Tânia Ferreira, Pedro Prudêncio, Rui Gonçalo Martinho. Drosophila Protein Kinase N (Pkn) is a negative regulator of actin-myosin activity during oogenesis. Developmental Biology  (2014) 10.1016/j.ydbio.2014.08.008.


Nurse cell dumping is an actinmyosin based process, where 15 nurse cells of given egg chamber contract and transfer their cytoplasmic content through the ring canals into the growing oocyte. We isolated two mutant alleles of protein kinase N (pkn) and showed that Pkn negatively-regulates activation of the actinmyosin cytoskeleton during the onset of dumping. Using live-cell imaging analysis we observed that nurse cell dumping rates sharply increase during the onset of fast dumping. Such rate increase was severely impaired in pkn mutant nurse cells due to excessive nurse cell actinmyosin activity and/or loss of tissue integrity. Our work demonstrates that the transition between slow and fast dumping is a discrete event, with at least a five to six-fold dumping rate increase. We show that Pkn negatively regulates nurse cell actinmyosin activity. This is likely to be important for directional cytoplasmic flow. We propose Pkn provides a negative feedback loop to help avoid excessive contractility after local activation of Rho GTPase.