Inducible DNA repair in Ustilago maydis.

Maximum survival of UV-irradiated U. maydis required a 2-3 h period of post-irradiation RNA and protein synthesis. Split dose experiments showed that this requirement correlated with the development of a radio-resistant cell state induced by UV doses above 200 Jm-2. Once induced, the radio-resistant state precluded the need for further RNA and protein synthesis for proficient repair of DNA damage caused by a second UV dose. Such radio-resistance was retained for up to 15 hours and it is concluded that this phenomenon represents the expression of an inducible DNA repair process, which is under transcriptional control.