Browsing by Author "Österman, Janina"

Pseudomonas syringae pv. tomato DC3000 is a Gram-negative plant pathogen that causes bacterial speck disease on tomato. The virulence of this bacterium is based on the type III secretion system (T3SS). Similar systems are also used by many other plant and animal pathogens, as well as symbiotic bacteria. The T3SS enables the transfer of specific bacterial virulence proteins from the bacterial cytoplasm into the host cell. This secretion is mediated by a needle-like structure that penetrates the plant cell wall. Once inside the host cells, the effector proteins are capable of shutting down the host’s immune system. However, what happens at the plant cell membrane is not well understood. One of the first bacterial proteins that come into interaction with a host protein during P. syringae pv. tomato DC3000 infection is the HrpZ1 protein that is believed to participate in a membrane interaction, facilitating the transfer of effector proteins. Previous research has shown that HrpZ1 binds to a peptide and using an antiserum raised against this peptide in immunoblotting tests of tomato proteins separated by SDS-PAGE and isoelectric focusing, the target tomato protein of HrpZ1 has been found to be small and acidic. However, this specific protein has not yet been fully characterized. This is why the goal of the work for this thesis was to identify and characterize the target protein of HrpZ1 in tomato. For this purpose, a lambda cDNA expression library from tomato leaves was constructed, followed by immunoscreening of the library with the abovementioned antiserum, and analysing candidate clones by sequencing. Even though a good cDNA library was obtained, the immunoscreenings did not yield satisfactory results. Thus, the pursuit of the HrpZ1 target protein needs to be continued.