Regulation of vegetative phase change in Arabidopsis thaliana by cyclophilin 40

During its development, a plant shoot progresses from a juvenile to an adul t phase of vegetative growth and from a reproductively incompetent to a rep roductively competent state. In Arabidopsis, Loss-of-function mutations in SQUINT (SQN) reduced the number of juvenile Leaves and had subtle effects o n inflorescence morphology but had no effect on flowering time or on reprod uctive competence. SQN encodes the Arabidopsis homolog of cyclophilin 40 (C yP40), a protein found in association with the Hsp90 chaperone complex in y east, mammals, and plants. Thus, in Arabidopsis, CyP40 is specifically requ ired for the vegetative but not the reproductive maturation of the shoot.