Elucidating the biological function of Arabidopsis DASH-type cryptochrome

dash型隐色素是隐色素/光解酶家族中最近发现的亚支系。隐色素是蓝光感受器，而DNA光解酶修复DNA中的紫外线损伤。dash型隐色素已在植物、真菌、许多细菌、真生动物和水生脊椎动物（如鱼类、两栖动物）中发现。在体外，它们修复单链和环结构DNA中的UV-B损伤。然而，缺乏光解酶的大肠杆菌对UV-B的敏感性并不能通过与dash型隐色素的互补来恢复。同样，在正常生长条件下以及在UV-B处理下，缺乏cry-DASH （cry3）的拟南芥突变体在表型上与野生型没有区别。因此，dash型隐色素作为dna修复酶的体内功能尚不清楚。我们建议采用遗传、生化和生理技术相结合的方法来破译拟南芥cry3的生物学作用。我们将尝试确定cry3是否仅作为光感受器或作为修复酶，或在这两个过程中具有双重功能或尚未涉及隐色素/光解酶家族成员的新功能。特别是，我们将寻找可能的cry3相互作用蛋白，并研究在遗传背景下缺乏隐色素或光解酶的cry3突变体的宏观和分子表型。

DASH-type cryptochromes constitute the most recently discovered subclade of the cryptochrome/photolyase family. Cryptochromes are blue-light photoreceptors, whereas DNA photolyases repair UV lesions in DNA. DASH-type cryptochromes have been identified in plants, fungi, many bacteria, eumetazoa, and aquatic vertebrates (e.g., fish, amphibians). In vitro, they repair UV-B lesions in single-stranded and loop-structured DNA. However, the UV-B sensitivity of photolyase-deficient Escherichia coli is not rescued by complementation with DASH-type cryptochromes. Likewise, Arabidopsis thaliana mutants deficient in cry-DASH (cry3) are phenotypically indistinguishable from wild type under normal growth-chamber conditions and also when treated with UV-B. Thus, an in vivo function of DASH-type cryptochromes as DNA-repair enzymes remains obscure. We propose to decipher the biological role of A. thaliana cry3 using a combination of genetic, biochemical, and physiological techniques. We will attempt to determine whether cry3 acts solely as a photoreceptor or as a repair enzyme, or has a dual function in both processes or a novel function not yet implicated for members of the cryptochrome/photolyase family. In particular, we will search for putative cry3-interacting proteins and study macroscopic and molecular phenotypes of cry3 mutants in genetic backgrounds lacking also cryptochromes or photolyases.