Host: The Japanese Society of Plant Physiologists
Pages 0216
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). We recently identified two homologous genes, KAC1 and KAC2, mediating chloroplast movement in Arabidopsis thaliana. In kac1 mutant, the accumulation response is drastically impaired and also the speed of chloroplast avoidance is slightly slower than in wild type. Although kac2 single mutant did not show any impairment in chloroplast movement, kac1kac2 double mutant lacks both the accumulation and avoidance responses. KAC1 protein and KAC1 mRNA accumulated at much higher level than those of KAC2 in wild type. KAC1 promoter-driven KAC2 expression completely rescued chloroplast photorelocation movement in kac1kac2. These results indicate that the difference between KAC1 and KAC2 is quantitative but not qualitative and that the abundance of KAC proteins is one of the critical determinants for speed of chloroplasts.
