Title : The lack of AtEgy1 protease leads to quantitative changes of photosystem II apoproteins in Arabidopsis thaliana
Abstract:
AtEgy1 chloroplast protease is the first intramembrane protease identified in plants, that belongs to the site-2-proteases (S2P), which are a relatively recently discovered class of proteases capable of catalyzing the proteolysis process within the biological membranes. AtEgy1 protease is a 59-kDa protein with 8 transmembrane domains. In the primary structure of this protein the motifs, characteristic for S2P proteases, responsible for the zinc ion binding e.g. HExxH and NxxPxxxxDG are present. Previous studies have shown that A. thaliana mutants lacking AtEgy1 protein exhibit marked changes in the number and ultrastructure of chloroplasts. Egy1 mutants are characterized by a poorly developed system of thylakoid membranes, lack of granum and markedly reduced plastoglobules size. Moreover, egy1 mutants showed the reduced chlorophyll level, resulting in the yellow color of the leaves. The lack of AtEgy1 protease can also cause disorders in the normal development of amyloplasts, which are important for the perception of gravitational stimulus. As a result, egy1 mutants exhibit the disorders of gravitropism.
The aim of this work was to analyze the quantitative changes in the proteins that build the core of photosystem II (PsbA, PsbC and PsbD) and the proteins that build up its major energy antennas (Lhcb1-6). It has been shown that the lack of AtEgy1 protease leads to significant changes in the levels of almost all tested proteins. The apparent decrease in the amount of Lhcb1-6, PsbC and PsbD had also impact on the parameters describing the quantitative effectiveness of PSII functioning.
This work was supported by the Polish National Science Center based on decision number DEC-2014/15/B/NZ3/00412.
