The four lysine-specific histone demethylases of Arabidopsis differentially contribute to the control of flowering time and defence responses

Individual histone modifications, or a specific combination of them, act as signals ('histone code') that are 'read' by other proteins able to influence chromatin structure and gene expression. Among them, histone methylation is an important epigenetic modification controlled by a balance between methylation and demethylation. In Arabidopsis, four lysine-specific histone demethylases (AtLSDs) are present. To determine their physiological roles, loss-of-function mutants and 35S::AtLSD transgenic plants were obtained and analysed under physiological and stress conditions. Furthermore, to determine the AtLSD specific targets, the expression levels of flowering regulators, as well of senescence and stress marker genes were assessed in the transgenic plants. The expression pattern of the four AtLSDs was also analysed in detail by histochemical staining of beta-glucuronidase (GUS) in AtLSD::GUS transgenic plants. Data indicate involvement of the various AtLSDs in the control of flowering time, as well as in defence responses to salt stress. Overall, this study highlights functional similarities, but also important differences among the four members of the AtLSD gene family.