Role of Cell Cycle Checkpoint in the Meristem Disorder of the tonsoku Mutants of Arabidopsis thaliana

Abstract

TONSOKU (TSK) of Arabidopsis thaliana is responsible for mutants defective in both shoot and root apical meristems, and it encodes a protein of unknown function⁽¹⁾. TSK is expressed in the S phase of the cell cycle⁽²⁾, and tsk mutants show enhanced expression of DNA damage-responsible genes and increased number of cells arrested at G2/M ⁽³⁾. DNA damage activates ATR and ATM checkpoint kinases and regulates the cell cycle. Phenotypes of tsk such as meristem disorders and enhanced expression of DNA damage-responsible genes, but not expression of heterochromatic TSI, were suppressed by atr. ATR-dependent cell-cycle arrest might be important in causing meristem disorder in tsk. We compared gene expression patterns in Col-0, tsk and tsk atr to understand the mechanism responsible for the meristem disorder in tsk. ⁽¹⁾Plant J. 38:673 (2004), ⁽²⁾Plant Cell Physiol. 46:736 (2005), ⁽³⁾Plant Cell 18:879 (2006).