Gizem Korkut

  • Date: –16:00
  • Location: Evolutionsbiologiskt centrum Lindahlssalen
  • Doctoral student: Student: Gizem Korkut Opponent: Dr. Javier Diéguez Uribeondo
  • Contact person: Gizem Korkut
  • Disputation

Interaction between crayfish and some microorganisms; Effect of temperature

My studies focused on understanding crayfish immunity with respect to temperature and white spot syndrome virus (WSSV) infection in freshwater crayfish, Pacifastacus leniusculus. Firstly, we elucidated a new WSSV interacting protein (PlcSP) that participates in WSSV replication by providing the virus with an attachment site on the host cell membrane. By knocking down this gene, we could prevent WSSV infection. Therefore, this protein seems to be essential for a successful WSSV infection.

Moreover, we aimed to investigate the cleavage site for this protein by expressing an active and inactive form of this protein in insect cell line and by using phage-substrate display technique we will be able to identify what this protease cleaves in the cascade.

Moreover, we investigated the effect of temperature on both WSSV infection and immunity. We found that in a quiescent state of host, the virus will remain silent until the conditions are optimal i.e. the host metabolism is active. In contrast to room temperature, at the lower temperatures in which the cell metabolism is quiescent, the infection was inhibited which we demonstrated by mortality and quantification of WSSV virions. Moreover, the virus was not even able to enter in neither HPT nor hemocytes. The expression of PlcSP which we have shown to be essential for viral entry is also inhibited at low temperatures which might explain our results. 

In order to understand if the temperature’s direct effect is on the host immunity or the pathogen itself, we repeated the same experiment with two gram-negative bacteria and LPS, whereby we could demonstrate that the cellular immunity is enhanced at low temperatures while the melanization is much higher in room temperatures which lead to higher mortalities due to production of excessive toxic compounds which harms the host.

By understanding crayfish immunity, we will be able to improve crustacean aquaculture which is an important source of income for shrimp and crayfish farmers, but more importantly we will be able to apply our knowledge to immune systems of other invertebrate animals.