Poster: Vegetative Development

Abs # 442: A dominant mutation in the JABBA gene affects Arabidopsis shoot apical meristem, leaf and gynoecium development

Presenter:	Fletcher, Jennifer C, fletcher@nature.berkeley.edu
Authors	Fletcher, Jennifer C (A) (B)  Grigg, Stephen  (A) (B)  Williams, Leor  (A) (B)  Brown, Hattie  (A) (B)  Christensen, Sioux  (C)
Affiliations:	(A): Plant Gene Expression Center (B): UC Berkeley Plant and Microbial Biology Dept. (C): UCLA Dept of MCD Biology
Web Site:	http://www.pgec.usda.gov/Fletcher/fletchlab.html

Plant growth and development depends upon the activity of shoot apical meristems (SAMs), which generate stems, leaves and flowers throughout the life cycle to attain the overall architecture of the plant. Our research objective is to understand the molecular mechanisms that control shoot and floral meristem function, and to determine how defects in meristem activity lead to alterations in plant morphology. We have identified a dominant, activation-tagged Arabidopsis mutant called jabba-1D (jba-1D) that has a greatly enlarged SAM, downward curling rosette leaves and a reduced gynoecium. We show that the jba-1D SAM defect occurs early in development, culminating in the fasciation and splitting of the flowering meristem. This phenotype is correlated with the detection of extremely high levels of STM expression in jba-1D SAMs. In addition, we observe STM mis-expression in young jba-1D leaf primordia, which may account for the leaf curling phenotype. We find that the JBA gene, which is over-expressed in jba-1D shoot apices and leaves, encodes a novel protein with a putative nuclear localization signal. In wild type plants, JBA is expressed at high levels in young floral buds and at very low levels in other tissues.