Abstract
Plants show changing of growth pattern responding to various environmental stimuli, such as light, gravity, temperature, and so on. Plants orientate their growth by monitoring the direction of light, a process known as phototropism. This response is the result of differential cell growth on the two sides of an elongating axis organ, such as a hypocotyl and a root. The Cholodny-Went hypothesis proposes that this differential growth is caused by a gradient of phytohormone auxin. To understand how light signaling pathways control the auxin distribution in plants, we are analyzing the molecular mechanisms of phototropism by using Arabidopsis phototropism mutants. Our study includes identifications and/or functional analyses of photoreceptors, phototropins, phytochromes and cryptochromes, signal transducers, RPT2 and NPH3, and auxin transporters, ABCB19 and PIN3. In this lecture, I introduce a current hypothetical model of the signaling pathways of phototropism, particularly in Arabidopsis hypocotyls.
