Abstract
Chloroplasts relocate in plant cells according to the ambient light conditions. Under the low-light conditions, chloroplasts accumulate in the light to capture weak light efficiently (accumulation response), while under the high-light conditions, they escape from the light to avoid photodamage (avoidance response). In a seed plant Arabidopsis thaliana, the accumulation response is mediated by two blue light receptors, termed phototropins (phot1 and phot2) that act redundantly, and the avoidance response is mediated by phot2 alone. Using a new screening method, we recently isolated a mutant, jac1 (J-domain protein required for chloroplast accumulation response 1), which lacks the accumulation response under weak blue light, but shows a normal avoidance response under strong blue light. Positional cloning of JAC1 gene reveals that this gene encodes a J-domain protein, resembling clathrin uncoating factor auxilin at its C-terminus. Amount of transcripts and encoded proteins of JAC1 gene were not regulated by light and phototropins.
