**5. Other responses**

In addition to DNA repair and TLS, UV-damaged DNA also triggers other cellular responses such as cell cycle arrest and cell death (Batista et al., 2009). In general, relatively little is known about the molecular basis of these responses in plants. As in mammalian systems, in plants the initial damage sensors include ATM (double strand breaks), ATR (ssDNA) and ATR-interacting protein ATRIP (Culligan et al., 2004; Furukawa et al., 2010; Sakamoto et al., 2009). Plants do not have a p53 homologue, in contrast damage signalling pathways converge on the SOG1 transcription factor, resulting in cell cycle arrest and cell death (Furukawa et al., 2010; Preuss & Britt, 2003; Yoshiyama et al., 2009). UV-induced cell death in plants also involves topoismerase I (Balestrazzi et al., 2010), metacaspase-8 and caspase-3-like activities (Danon et al., 2004; He et al., 2008; Zhang et al., 2009), as well as changes in reactive oxygen species and mitochrondria (Gao et al., 2008).
