Abstract
Growth and development in plants are supported by continuous supply of dividing cells in meristems. The cell division activity is maintained under environmental stress conditions. However, underlying mechanisms for the maintenance of meristematic activity in such circumstances are not well understood. In this study, we show that RSS1, which is required for environmental stress tolerance in rice, is involved in the machinery to ensure cell division activity under salinity. RSS1 encodes a novel protein with D-box, which is important for cell cycle-dependent protein degradation, and is preferentially expressed in dividing cells at G1 to S phase. In the shoot basal region of rss1, progression of cell cycle is inhibited at G1 under salinity. In the root tip of rss1, both meristematic and elongation zones were diminished depending on salinity. This is mimicked in wild-type root treated with DNA synthesis inhibitor, indicating that decrease of cell division activity accounts for the rss1 phenotype under salinity. The role of RSS1 in the mechanisms to ensure cell cycle and for stress tolerance will be discussed with the action of cytokinins, as well as evolutionary history of angiosperms.
