Involved in repair of UV radiation-induced DNA damage. Catalyzes the light-dependent monomerization (300-600 nm) of cyclobutylpyrimidine dimers (CPDs), which are formed between adjacent bases on the same DNA strand upon exposure to ultraviolet radiation. Required for plant survival in the presence of UV-B light. Not involved in the repair of (6-4) photoproducts. cyclobutadipyrimidine (in DNA) = 2 pyrimidine residues (in DNA). Binds 1 FAD per subunit. Highly expressed in flowers. Expressed in roots and stems. By high-fluence white light, UV-A and UV-B. No visible phenotype under white light, but inhibition of growth and leaf necrosis under white light and UV-B. Increased accumulation of CPDs under UV-B. Over-expression of PHR1 decreases CPDs accumulation during UV-B treatment. Belongs to the DNA photolyase class-2 family.