新制癌菌素和平阳霉素诱发蚕豆染色体畸变的比较研究

本文报道了新制癌菌素(NCS)能诱发植物染色体畸变,同时观察了利用咖啡因后处理对NCS、PYM诱发染色体畸变的影响,研究了PYM切断DNA断头的性质。结果表明,NCS切割DNA产生3'-羟基末端和3'-磷酸末端;咖啡因能封闭3'-羟基末端抑制DNA的修复,从而提高诱变频率。PYM加咖啡因后处理,其染色体畸变频率与PYM单独处理无明显差异。说明PYM切断DNA所得到的产物,不是3'-羟基末端,而是3'-磷酸末端。

Comparative Study on Chromosome Aberrations Induced by Neocarzinostation and Pingyangmycin in Vicia faba

Neocarzinostatin (NCS) is an antitumor antibiotic of protein native.It has been reported that NCS causes DNA strand breakage,inhibits DNA synthesis and cell division.Chromosome aberration has been induced by NCS in animal cells.But no reports have been published so far about its mutagenic effects on plant cells.Previous results in this laboratory revealed that pingyangmycin (PYM) is a strong mutagen for chromosome aberration induction in plants.Early results also suggested that its high mutagenecity might be due to that the damage caused by pingyangmycin could not be repaired by DNA polymerase.Sites of strand scission on NCS-trested DNA bear either terminal 3'-hyd-roxyl or 3'-phosphoryl group.Gaps in DNA bounded by 3'-hydroxyl and 5'-phosphory termini is right termini for repair.Caffeine blocked the 3'-hydroxyl termini and thus inhibits DNA repair,promote chromosome aberration.In this paper induction of chromosome aberration by NCS and PYM alone or with caffeine post-treatment were compared,and the nature of the 3'-termini of the PYM-induced strand breakage was discussed base on the comparison.Experimental results indicated the percentage of chromosome aberrations induced in root tip cell of Vicia faba by NCS-treatment were 27.73%,while by EMS and PYM were 18.58% and 36.03% respectively.Caffeine post-treatment enhanced chromosome aberrations from 27.73% to 46.20% in NCS mutagenesis.The types of aberrations and number of micronuclei were also increased.This is consisted with the early observation that gaps in DNA induced by NCS bear either 3'-hydroxyl or 3'-phosphoryl termini.Caffeine blocked the 3'-hydroxyl group,inhibited the repairing,thus raised the percentage of chromosome aberrations.Caffeine post-treatment did not increase chromosome aberration in PYM mutagenesis suggested that the strand breakages caused by PYM were not terminal 3'-hydroxyl but 3'-phosphoryl group,and no appropriate terminal group were provided for caffeine blocking.