Differential responses to UV-B irradiation of three near isogenic lines carrying different purple leaf genes for anthocyanin accumulation in rice (Oryza sativa L.)

We produced near isogenic lines (NILs) for three purple leaf genes, Pl, Pl^w and Plⁱ of rice with a genetic background of T-65 to characterize each allele. Three NILs each had characteristic tissue-specific anthocyanin pigmentation. T-65 Pl^w was newly found to make the root purple when the root was exposed to light. To explore the inducible characteristics of the three genes, we examined the responses of the three NILs to UV-B irradiation. Although the accumulation of anthocyanin increased in all NILs with the increase in the intensity of UV-B irradiation, we observed differential responses for the accumulation of anthocyanin in the NILs: T-65 Plⁱ accumulated the largest amounts of anthocyanin under weak and intermediate intensity of UV-B, though this NIL reduced anthocyanin accumulation under a high intensity of UV-B. T-65 Pl or Pl^w increased anthocyanin accumulation with increasing intensity of UV-B. Anthocyanin accumulation of the Pl NIL was higher than that of the Pl^w NIL under each intensity of UV-B. In addition, the total biomass of all the irradiated NILs decreased with the increasing dose of UV-B irradiation and the decrease was negatively correlated with the increase in anthocyanin accumulation in the dose range of UV-B irradiation.