Abstract
We have isolated a paraquat-resistant mutant of Arabidopsis (rcd1-2), which was found to be an allele of RCD1. rcd1 had been known as hypersensitive to ozone (Overmyer et al., 2000; Ahlfors et al., 2004). rcd1-2 was tolerant to short-term UV-B exposure. It contained higher amounts of sunshade pigments as well as mRNA of plastidic Cu/Zn superoxide dismutase and stromal ascorbate peroxidase, which are likely to be causes of higher tolerance of rcd1 to UV-B and paraquat. We found that RCD1 encoded CEO1 which appears to function as a transcriptional regulator (Belles-Boix et al., 2000). Thus, RCD1 seems a constitutive repressor to various stress responses, disruption of which induces hypersensitive responses to them. We generated RCD1 overexpressors, and found that they were more sensitive to ozone than wild type but less so than rcd1; they were not resistant to paraquat; and they complemented rcd1 defects when introduced to rcd1 by crossing.
