DNA Damage Checkpoint Response in Plants

University Of California-Davis, Davis CA

Investigators

Abstract

Britt, A. Although some of the genes encoding the direct regulators of the cell cycle have been identified in plants, virtually nothing is known as to whether DNA damage induced cell cycle arrest occurs in plants. However, there are certain interesting effects of DNA damaging agents on plant growth, which suggest that cell cycle arrest is taking place. When plants are treated as seeds with very high levels of gamma radiation, the seed survives, germinates at a normal rate, develops normally in respect to its environment but does not produce any new cells. All growth occurs through cell expansion and a plant that possesses only its embryonic leaves results, a "gamma plantlet". Mutants have been obtained defective in DNA repair that are hypersensitive to the gamma-plantlet inducing effects of gamma radiation. The genes that are required for detecting the persistence of DNA damage and transducing that information to the direct regulators of the cell cycle will be sought. More importantly, a genetic screen for mutants defective in this process will be performed. The screen will allow identification of any genes required for this process which are unique to plants or which have not yet been identified in animals. Second site suppressors of the gamma plantlet phenotype in the DNA repair mutant line will be obtained. In order to reduce the frequency of induction of mutations, most living things have developed mechanisms for the detection of persisting DNA damage and the transduction of this information to the regulators of the cell cycle. These damage-specific "checkpoints" provide the cell with time in which to repair DNA damage before it is processed into a mutation. Cells defective in DNA damage-specific checkpoints are both hypermutable and hypersensitive to the toxic effects of many DNA damaging agents.