54:	Overexpression of AtFtsZ1-1 alters chloroplast division in Arabidopsis.

Authors:	Stokes, Kevin, D.(A)Figueroa, Rubi(A)McAndrew, Rosemary, S.(A)Osteryoung, Katherine, W.(A)
Affiliations:	(A): University of Nevada, Reno
Presenter:	Stokes, Kevin D., kstokes@med.unr.edu

Chloroplast division is critical for plant growth and development. We have identified two nuclear genes from Arabidopsisencoding homologues of the bacterial cell division protein FtsZ, a component of the prokaryotic cell division machinery. AtFtsZ1-1 is imported into the chloroplast in vitrowhereas AtFtsZ2-1 is not. However, antisense repression of either gene results in plants with dramatically reduced numbers of enlarged chloroplasts in mesophyll cells (Osteryoung et al., 1998, Plant Cell 10:1991-2004). To learn more about FtsZ function in plastid division, we have generated transgenic Arabidopsisplants that overexpress AtFtsZ1-1. Like the antisense plants, many of the AtFtsZ1-1overexpressing lines have decreased numbers of enlarged chloroplasts, indicating an inhibition of chloroplast division. Analysis of AtFtsZ1-1 RNA and protein levels in these plants indicates that this phenotype is the result of overexpression and not cosuppression. Despite reduced chloroplast numbers, these plants exhibit no obvious defects in growth or development. Among the transgenic lines we have also observed a few with smaller but more numerous chloroplasts compared to wild type, indicative of increased plastid division. However, these plants have been pale and small, and have not survived past seedling stage. Overexpression and subsequent analysis of AtFtsZ2-1 in Arabidopsisis currently being performed. Supported by grants from the NSF and the Nevada Agricultural Experiment Station.