Abstract
Excess boron (B) is toxic to plants. However molecular mechanisms of B toxicity are poorly understood. We previously isolated and characterized Arabidopsis mutants sensitive to excess B and found two responsible genes, CAP-H2 and CAP-G2. Both genes encode regulatory subunits of chromosomal protein complex, condensin II, suggesting that the function of condensin II complex was crucial for excess B tolerance in Arabidopsis. Recently, it has been reported in yeasts and mammals that condensin is involved in DNA damage repair as well as mitotic chromosomal condensation. In the present study, we elucidated whether excess B causes DNA damage. We found that the root growth of cap-h2 were sensitive to DNA damaging agents (MMS). And cap-h2 showed higher expression levels of DNA damage inducible (DDI) genes such as RAD51 and ATGR1 in root tip. Furthermore, excess B induced DDI genes expression in both wild type and cap-h2. These results indicate that Arabidopsis condensin II is also involved in DNA damage reparation and excess B possibly causes DNA damage in roots. To confirm the DNA damage by excess B, quantitative analysis of DNA damage is in progress.
