Abstract

UV-B radiation affects plant growth inhibiting cell proliferation. This inhibition is in part controlled by the activity of transcription factors of the E2F family. In particular, the participation of E2Fc and E2Fe in responses to UV-B in Arabidopsis plants was previously reported. However, the contribution of E2Fa and E2Fb in these processes has not been yet investigated. Thus, in this work, we provide evidence that, in Arabidopsis, both E2Fa and E2Fb control leaf size under UV-B conditions without participating in DNA damage repair. On the contrary, in seedlings exposed to UV-B, E2Fa but not E2Fb regulates primary root elongation, cell proliferation and programmed cell death in the meristematic zone. Using e2fa mutants that overexpress E2Fb, we here demonstrate that the role of E2Fa in the roots cannot be replaced by E2Fb. Finally, the results presented show that E2Fa and E2Fb differentially regulate the expression of genes that activate the DNA damage response, both under conditions without UV-B and after exposure. Together, we here show that both E2Fa and E2Fb have different and non-redundant roles in developmental and DNA damage responses in Arabidopsis plants exposed to UV-B radiation.