Genetic Analysis of Radiation Response in Plants

作为新陈代谢的产物，植物经常暴露在来自太阳和氧气的UV-B光下，两者都可以并且确实会损害DNA。因此，植物可能会利用有效的机制来修复这些类型的DNA损伤。对紫外光异常敏感的拟南芥突变体已经被分离出来，并发现包含几个在不同位置的互补基团。目前正在研究两个初步鉴定为参与紫外线损伤的核苷酸切除修复途径的编码产物的基因。定位克隆UVH1和UVH3的尝试正在进行中。初步证据表明，UVH1位点可能是人类XP-B基因的同源物，XP-B基因是人类遗传性疾病着色性干皮病的几个互补群之一，以及酵母Rad 25基因。将完成这些基因的克隆，进行互补试验，并对突变基因进行测序。放射免疫试验和适当酵母突变体的补充将进一步探索基因的功能。对环境条件变化的响应，如紫外光强度和氧气生产的变化，转录调控的修改将被研究。更多的拟南芥切除修复基因将被鉴定、表征和定位。植物需要高效的机制来去除和修复DNA损伤，因为它们经常暴露在阳光和分子氧中，这两种因素都会导致DNA损伤。由于植物的生殖器官是由未分化的体细胞组织发育而来的，这一任务在植物中变得更加重要。从这项正在进行的研究中获得的信息将使我们对修复过程有更深入的了解。

Mount MCB 978125 Plants are constantly exposed to UV-B light from the sun and oxygen as a product of metabolism and both can and do damage DNA. Hence, plants are likely to utilize efficient mechanisms for repairing these types of DNA damage. Mutants of Arabidopsis that are abnormally sensitive to UV light have been isolated and found to comprise several complementation groups that map in different locations. Two genes, which have been tentatively identified as encoding products which are involved in the pathway for nucleotide excision repair of UV damage are under study. An attempt to positionally clone UVH1 and UVH3 is underway. Preliminary evidence suggests that the UVH1 locus may be a homolog of the human XP-B gene, a gene which is one of the several complementation groups involved in the human genetic disease xeroderma pigmentosum, as well as the yeast Rad 25 gene. The cloning of these genes will be completed, complementation tests performed and mutant genes sequenced. A radioimmune assay and complementation of the appropriate yeast mutants will further explore the function of the genes. The response to changing environmental conditions such as variation in UV light intensity and oxygen-production by the modification of transcriptional regulation will be investigated. Additional Arabidopsis excision repair genes will be identified, characterized and mapped. Plants can be expected to require highly efficient mechanisms for removal and repair of DNA damage since they are constantly exposed to sunlight and molecular oxygen, both factors known to cause DNA damage. Since the reproductive organs of plants are developmentally derived from undifferentiated somatic tissues, that task becomes even more critical in plants. Information derived from this on-going study will give greater insight into that repair process.