A genetic screen for components involved in resistance (R) protein-mediated immunity in Arabidopsis led to isolation of crt1 ( c ompromised r ecognition of T CV). CRT1 was shown to be a MORC ATPase/endonuclease that physically interacts with multiple immune components. While CRT1 is mainly located in endosome-like vesicles in the cytoplasm, a subpopulation resides in the nucleus, which increases after infection. The combined findings that CRT1 i) is an endonuclease, ii) physically interacts with several components of the DNA repair and recombination (R/R) pathway, iii) is localized to heterochromatin, and iv) is implicated in epigenetic regulation, including suppression of heterochromatic transposable elements (TEs), suggest that CRT1 has an important nuclear function(s). Thus, we are investigating CRT1’s role in the nucleus, particularly its involvement in stress-triggered genome stability, and to assess the importance of this function in plant immunity and evolution.
To assess whether stress-triggered genome stability is regulated by CRT1, Southern blot analysis and second-generation sequencing are currently performed on consecutive generations of pathogen-inoculated wild type (WT) and mutant plants lacking CRT1 and its closest homolog CRH1. We are also testing whether trans-generational genomic instability facilitates development of novel alleles that enhance plant resistance to biotic stress. To investigate the function of nuclear CRT1, we altered CRT1 location (by fusion with a nuclear localization or nuclear exclusion signals) and monitored both disease resistance and the ability of these constructs to bind known DNA R/R proteins.