Evidence for the involvement of protein lysine methylation in the response of sensitive and tolerant Arabidopsis species to cadmium stress

The mechanisms underlying the response and adaptation of plants to excess of trace elements are not fully described. Here, we analyzed the importance of protein lysine methylation for plants to cope with cadmium. We analyzed the effect of cadmium on lysine-methylated proteins and protein lysine methyltransferases (KMTs) in three Arabidopsis species. Arabidopsis thaliana and A. lyrata were used as cadmium-sensitive models and compared with three populations of A. halleri with different properties of accumulation and tolerance to cadmium. Immunoblotting, protein mass spectrometry, and gene expression analysis showed that the expression of some lysine-methylated proteins and genes coding KMTs is regulated by cadmium. Using a genetic screening, we showed that nine A. thaliana mutants interrupted in KMT genes have a tolerance to cadmium that is significantly different from that of wild-type seedlings. We further characterized two of these mutants, one was knocked-out in the calmodulin lysine methyltransferase gene and displayed increased tolerance to cadmium, the other was interrupted in a KMT gene of unknown function and showed a decreased capacity to cope with cadmium. Together, our results showed that the fine-tuned regulation of nonhistone proteins by lysine methylation has a role in the response of Arabidopsis plants to cadmium stress