K├╝hnlenz, T; Westphal, L; Schmidt, H; Scheel, D; Clemens, S: Expression of Caenorhabditis elegans PCS in the AtPCS1-deficient Arabidopsis thaliana cad1-3 mutant separates the metal tolerance and nonhost resistance functions of phytochelatin synthases, Plant, Cell and Environment, 38, 2239–2247 (2015), doi:10.1111/pce.12534
Phytochelatin synthases play key roles in plant metal tolerance. They synthesize small metal-binding peptides, phytochelatins, under conditions of metal excess. Respective mutants are strongly cadmium and arsenic hypersensitive. However, their ubiquitous presence and constitutive expression had long suggested a more general function of phytochelatin synthases (PCS) besides metal detoxification. Indeed, phytochelatin synthase1 from Arabidopsis thaliana (AtPCS1) was later implicated in nonhost resistance. The two different physiological functions may be attributable to the two distinct catalytic activities demonstrated for AtPCS1, i.e. the dipeptidyl transfer onto an acceptor molecule in phytochelatin synthesis, and the proteolytic deglycylation of glutathione conjugates. In order to test this hypothesis and to possibly separate the two biological roles we expressed a phylogenetically distant PCS from Caenorhabditis elegans in an AtPCS1 mutant. We confirmed the involvement of AtPCS1 in nonhost resistance by showing that plants lacking the functional gene develop a strong cell death phenotype when inoculated with the potato pathogen Phytophthora infestans. Furthermore, we found that the C. elegans gene rescues phytochelatin synthesis and cadmium tolerance but not the defect in nonhost resistance. This strongly suggests that the second enzymatic function of AtPCS1, which remains to be defined in detail, is underlying the plant immunity function.

last modified 2015-12-15