45001:

The isolation and characterization of leunig, a regulator of Arabidopsis flower and ovule development.

Authors:	Conner, Joann, A.(A)Klink, Vincent, P.(A)Liu, Zhongchi(A)
Affiliations:	(A): Dept. of Cell Biology and Molecular Genetics, Univ. of Maryland (B): Dept. of Horticulture, Univ. of Georgia
Presenter:	Liu, Zhongchi , ZL17@umail.umd.edu

Floral development in Arabidopsis has been extensively studied through the utilization of floral mutants. Floral development in Arabidopsis is controlled by the activity of homeotic genes that specify floral organ identity and by the activity of cadastral genes which maintain the boundaries of activity of the homeotic genes. LEUNIG (LUG) is a cadastral gene involved in establishing the boundary of the AGAMOUS (AG) expression during floral development. Mutations in lug causes ectopic expression of AG in the first two whorls of a flower, resulting in the conversion of sepals to carpels and petals to stamen-like filaments or absent. Thus, LUG likely encodes a negative regulator of AG expression. In addition to the cadastral activity of LUG in floral development, lug mutants have reduced female fertility, unfused carpels, and narrow leaves and floral organs. These diverse effects of lug mutations indicate that LUG is involved in the regulation of several different developmental processes. Analyses of ovule development in lug single and double mutants indicate that LUG and AINTEGUMENTA (ANT) play an important yet redundant role in regulating ovule initiation. While single lug or ant mutants can still initiate ovule primordia, double mutants of lug ant do not form any ovules in their carpels. This effect of lug ant double mutations in ovule initiation is not caused by ectopic AG expression. Thus LUG and ANT may regulate other unidentified genes to exert their roles in ovule initiation. A map-based cloning approach is being used to isolate LUG. LUG is located between marker g8300 and AtH1 on chromosome 4. Fine mapping has placed LUG in a 300KB region. A cosmid library has been constructed from the YAC (yeast artificial chromosome) that contains LUG. A cosmid contig covering this 300KB region has been introduced into lug mutant plants by the vacuum-infiltration method. A cosmid has been identified that rescued the phenotype of lug mutants. Further analyses of the cDNAs isolated from this cosmid will allowed us to confirm the cloning of LUG. By focusing on the genetic and molecular analyses of LUG, the control mechanisms for region-specific gene expression, pattern formation and organ initiation will be dissected in Arabidopsis.