Abstract
Autophagy is a degradative pathway of cellular components. It occurs widely in the eukaryote. In plant autophagy, it has been thought that autophagosomes and/or autolysosomes, which are formed during the proceeding of autophagy, eventually fuse with vacuoles. We have reasoned that such fusions cause the expansion of vacuoles and the elongation of cells. In this study, we have examined whether autophagy is related to cell elongation or not.
We excised root tips of 5 mm long from Arabidopsis seedlings and incubated them for 2 to 3 days in a culture medium. The root tips elongated when sucrose was present in the medium, but hardly elongated when sucrose was absent. This result shows the elongation of root tips largely depends on sucrose in the medium in our experimental system. The elongation that occurs in the presence of sucrose was inhibited by addition of the protease inhibitor E-64d and of the autophagy inhibitor 3-methyladenine into the medium. Furthermore, mutants, in which the autophagy-related gene ATG5 is disrupted, exhibited slower elongation growth than the wild type. These results show that autophagy contributes to cell elongation.
