Poster: Seed biology

Abs # 725: Characterization of ABA-insensitive mutants expressing random GFP:DNA fusions in Arabidopsis

Presenter:	Chow, Brenda Y, chow@botany.utoronto.ca
Authors	Chow, Brenda Y (A)   McCourt, Peter  (A)
Affiliations:	(A): University of Toronto

The phytohormone abscisic acid (ABA) regulates many processes throughout plant development, including the establishment of seed dessication tolerance and dormancy. ABA also mediates the response to environmental stresses such as cold and drought. Despite its potential in agricultural applications, a complete genetic pathway for the conversion of ABA into a biological response remains elusive. Genetic screens for positive regulators of the ABA response in germination in Arabidopsis have identified protein phosphatases (ABI1 and ABI2), transcription factors (ABI3, ABI4, and ABI5) and a novel protein (ABI8), but no clear signaling pathway has been established. To identify other genes controlling the ABA response in germination, we have undertaken a genetic screen for additional ABA-insensitive mutants in Arabidopsis lines expressing random GFP:DNA fusions. This approach can identify new dominant mutations since fusions are expressed under the 35S constitutive promoter and were generated from genomic DNA as well as mRNA isolated from etiolated seedlings and callus tissue. This screen has identified ABA-insensitive mutants, including one with defects in cotyledon development. Upon germination in both the presence and absence of ABA, cotyledons are white and unexpanded, while the hypocotyl is elongated and photosynthetic. For the development of true leaves, supplementation of the growth media with sucrose is required. We are currently analyzing all the mutants identified in this screen using both genetic and physiological approaches. Characterization of these mutants will further improve our understanding of the role of ABA in germination.