ELF3-1 protein stability responds to light. (A) Anti-ELF3 specifically recognizes ELF3-1, which occurs in two bands during darkness. During light periods, only the higher (H) band is present. During SD (10-h day, 14-h night) the low (L) band is able to accumulate during the long night. (B) In the phyb background ELF3-1 loses photoperiod responsiveness, and both H and L bands are present in both light and dark periods. (C) The reduction in ELF3-1 levels in response to light is rapid, with only 15 min of NB being sufficient.