Shedding light on auxin movement: light-regulation of polar auxin transport in the photocontrol of plant development.

By being sessile, plants have evolved a remarkable capacity to perceive and respond to changes in environmental conditions throughout their life cycle. Light represents probably the most important environmental factor that impinge on plant development because, other than supplying the energy source for photosynthesis, it also provides seasonal and positional information that are essential for the plant survival and fitness. Changes in the light environment can dramatically alter plant morphogenesis, especially during the early phases of plant life, and a compelling amount of evidence indicates that light-mediated changes in auxin homeostasis are central in these processes. Auxin exerts its morphogenetic action through instructive hormone gradients that drive developmental programs of plants. Such gradients are formed and maintained via an accurate control on directional auxin transport. This review summarizes the recent advances in understanding the influence of the light environment on polar auxin transport.