Studies of DNA repair in various plants using the comet assay

By using isolated nuclei instead of whole cells, the comet assay can be ado pted for virtually any plant. In this report we compare Vicia faba, a 'stan dard' plant for cytogenetic studies, and Arabidopsis thaliana, at present t he most widely used model plant. X-rays, N-methyl-N-nitrosourea (MNU) and methylmethanesulfonate (MMS) were studied for their potential to induce comets. We show a substantial depende nce of comet formation on electrophoretic conditions after X-ray irradiatio n rather than on conditions of lysis and unwinding. With the A/N assay (alkaline unwinding and neutral electrophoresis), less D NA damage - both DNA breaks and AP sites (detected as sites sensitive to ex onuclease III) - is observed when pretreatment with a low dose of alkylatin g agents MNU or MMS is followed by a high (challenge) dose, compared with a pplication of only the high dose. Surprisingly, such adaptation followed by comet assay is not induced in Ara bidopsis.