Poster: Cell division

Abs # 673: Tousled-like Kinases of maize are up-regulated during endosperm development and can functionally complement the tousled mutant of Arabidopsis

Presenter:	Owusu, Owusuwaa E, owusuo@science.oregonstate.edu
Authors	Owusu, Owusuwaa E (A) (A)  Rivin, Carol J (B) (B)
Affiliations:	(A): Oregon State University, Dept. Biochemistry and Biophysics (B): Oregon State University, Dept. Botany and Plant Pathology

The Tousled-like kinases (tlks), are a conserved family of nuclear ser/thr kinases in plants and animals. Tlks have been implicated in chromatin remodeling activity during DNA replication and repair: They are maximally active during interphase of the cell cycle; they can phosphorylate histone H3 and interact with Asf1, a histone chaperone; they are targets of the DNA damage checkpoint kinases ATM and Chk1 (Carrera et al, 2003, Sillje et al, 1999, Groth et al 2003, Sillje and Nigg, 2001). In Arabidopsis, mutations in the TOUSLED (TSL) gene cause major abnormalities in floral development, suggesting that they may play a role in gene expression modulation through chromatin remodeling (Roe et al, 1993, 1997). Zea mays has three tlk genes that fall into two classes: zmTLK2 and zmTLK3 are more closely related to each other than to zmTLK1. In the catalytic region, the zmtlks are 84% identical to TSL. The regulatory domains are less conserved in sequence, but have similar structural features. ZMTLK2 expressed as a transgene in Arabidopsis tsl mutant plants completely rescues mutant phenotype, indicating that the maize protein can interact with the appropriate signaling partners for proper floral development. The zmtlk genes are ubiquitously expressed and show somewhat higher expression in dividing tissue, including young floral tissue. What is notable in maize is a dramatic increase in the expression of the ZMTLK2/3 genes during endosperm development. The time of up-regulation corresponds with a period of genome reduplication and chromatin restructuring in the endosperm. We hypothesize that both classes of zmtlks take part in a general system for chromatin remodeling during DNA replication/repair, while zmtlk2/3 have a specific role in endosperm development.