Abstract
Under low-light conditions, chloroplasts accumulate in the light to capture weak light efficiently (accumulation response), while under high-light conditions, they escape from the light to avoid their 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. We recently isolated a mutant, kac1, which is deficient in chloroplast photorelocation movement. Map-based cloning revealed that KAC1 gene encodes a novel protein specific to plants. KAC1 transcripts are detected in leaves, stems, flowers and roots. KAC1 proteins are enriched in soluble fraction and are detectable also in microsomal fractions. The amount and the localization pattern of KAC1 proteins do not change in mutants, phot1phot2, jac1 and chup1, which are deficient in chloroplast photorelocation movement, comparing to those of wild type plants.
