Abstract
Cucumber seedling grown in a horizontal position develops a peg on the lower side of the transition zone between the hypocotyl and the root. In contrast, vertically grown cucumber seedling forms a peg on each side of the transition zone. We have suggested that gravistimulation decreases auxin and suppresses the peg formation on the upper side of the transition zone. To understand the mechanism for the gravity-regulated distribution of auxin in the transition zone, we investigated the localization of CsPIN1 auxin efflux carrier in the transition zone by immunohistochemical analysis. We found that the localization pattern of CsPIN1 protein in endodermis of the transition zone of horizontally grown cucumber seedlings differs from that of vertically grown seedlings. These results suggest that the gravity-modified localization of CsPIN1 in endodermis contributes to the regulation of auxin distribution in the transition zone of cucumber seedlings.
