Mutagenic synergism detected between 1,2-dibromoethane and X rays in the stamen hairs of Tradescantia clone BNL 4430.

Abstract

Mutagenic interaction between 1,2-dibromoethane (EDB) and X rays was studied in the stamen hairs of Tradescantia clone BNL 4430, a blue/pink heterozygote. The young inflorescence-bearing shoots with roots of this clone cultivated in a nutrient solution circulating growth chamber were used as the tester plants. EDB is a promutagen and also a bifunctional alkylating agent with a high Swain-Scott substrate constant, but is thought to react probably via SN 1 mechanism. After confirming the dose-dependent mutagenicities of aqueous solutions of EDB for the first time in Tradescantia stamen hairs, a combined treatment with EDB and X rays was conducted, exposing acutely to 578 mGy X rays at the midpoint of 66.5 mM EDB treatment for 4 h. The induced somatic mutation frequency determined after the combined treatment was significantly higher (at 0.1% level) than that expected from the additive effects of EDB and X rays, showing that EDB and X rays acted obviously synergistically. The confirmation of the mutagenic synergism between EDB and X rays is reported here for the first time, although a likelihood of synergistic effects of EDB with 3 H beta rays has been suggested earlier.

Antagonistic effects of ethyl methanesulfonate and maleic hydrazide in inducing somatic mutations in the stamen hairs of Tradescantia clone BNL 4430.

“…It has been considered that mutagenic synergisms occur between different mutagens which have some interrelated or at least partly common mechanisms of action, and that no synergism would appear between different agents which cause entirely different damages on DNA (Shima and Ichikawa, 1994). It has also been thought most likely that DNA single-strand breaks produced commonly by X rays and several alkylating agents or promutagens are the major cause of the mutagenic synergisms observed earlier (Ichikawa et al, 1993;Ichikawa, 1995, 1997;Xiao and Ichikawa, 1995, 1998a, 1998b.…”

“…Based on the 3-week daily scorings of the numbers of hairs and pink mutants events (PMEs) as well as the average number of cells per hair, daily somatic mutation frequencies as the numbers of PMEs per 10 4 hair-cell divisions were calculated for each treatment. The data were pooled for the 4-day peak period of mutation frequency for each treatment as in earlier studies (Ichikawa et al, 1993;Shima and Ichikawa, 1994Xiao and Ichikawa, 1995, 1998a, 1998b.…”

“…In the present study, mutagenic interaction between EMS and MH was investigated in the stamen hairs of Tradescantia clone BNL 4430 which has been used in earlier related studies (Ichikawa et al, 1993;Shima and Ichikawa, 1994Xiao and Ichikawa, 1995, 1996, 1998a, 1998b. Since EMS has been shown to act synergistically with X rays (Cebulska-Wasilewska et al, 1981;Shima and Ichikawa, 1994), and MH has also been shown to act synergistically with X rays when exposed to X rays before MH treatments , EMS and MH were expected to act synergistically at least by exposing to EMS before MH treatment.…”

“…The involvement of peroxidase in activating MH into a mutagen in the floral tissues has been shown to be very likely, and the occurrences of such synergisms and antagonisms between MH and X rays have clearly been related to increases and decreases, respectively, in peroxidase activity (Xiao and Ichikawa, 1996). Mutagenic synergism has also been detected between X rays and 1,2-dibromoethane (EDB), a promutagenic and bifunctional alkylating agent (Xiao and Ichikawa, 1998b).…”

Further yearly analyses of spontaneous pink mutant events in the stamen hairs of Tradescantia clone BNL 4430 cultivated in the NSC growth chamber.

“…The system has also been shown to be suitable for studying the variation in spontaneous somatic mutation frequency (Takahashi and Ichikawa, 1976;Schairer and Sautkulis, 1982;Schairer et al, 1983;Ichikawa 1984Ichikawa , 1992Ichikawa , 1994Imai et al, 1991;Sanda-Kamigawara et al, 1991Ichikawa et al, 1995Ichikawa et al, , 1996aIchikawa et al, , 1996bIchikawa and Wushur, 2000). The use of the young inflorescencebearing shoots with roots of clone BNL 4430 cultivated in a recently developed nutrient solution circulating (NSC) growth chamber (Shima and Ichikawa, 1994;Ichikawa and Wushur, 2000) has been shown to be especially efficient for detecting mutagenic synergisms (Shima and Ichikawa, 1994Xiao and Ichikawa, 1995, 1996, 1998a, 1998b or antagonisms (Xiao and Ichikawa, 1995, 1996, 1998a, 1998c among various chemicals and X-rays, making it possible to determine spontaneous background mutation frequencies with higher accuracy than before Ichikawa and Wushur, 2000).…”