Abstract
FtsH is an ATP-dependent metalloprotease and present as a hetero-complex in thylakoid membranes. FtsH2, encoded in Arabidopsis VAR2 locus, is a major isoform. Mutants lacking FtsH2 (var2) result in a typical leaf-variegated phenotype. In this study, we assessed the importance of the catalytic center (zinc-binding domain) in FtsH2. We generated transgenic var2 and var1 var2 plants expressing a proteolytically-inactive version of FtsH2 (H488L). Expression of FtsH2 (H488L) in var2 rescued leaf variegation. On the other hand, expression of FtsH2 (H488L) in var1 var2 did not fully rescue the variegation phenotype. In mature leaves, H488L seemed to slow the rate of D1 protein degradation but did not lead to photoinhibition in vivo. Thus, the protease activity of FtsH2, though slightly affecting D1 degradation, is dispensable. Our results suggest that all the catalytic domains are not necessary when provided by at least several FtsH isomers.
