ISOLATION AND CHARACTERIZATION OF ABSCISIC ACID-DEFICIENT ARABIDOPSISMUTANTS AT 2 NEW LOCI

Novel Arabidopsis mutants with lowered levels of endogenous abscisic a cid (ABA) were isolated. These were selected in a screen for germinati on in the presence of the gibberellin biosynthesis inhibitor paclobutr azol. Another mutant was isolated in a screen for NaCl tolerance. The ABA-deficiency was caused by two monogenic, recessive mutations, aba2 and aba3, that were both located on chromosome 1. The mutants showed a phenotype that is known to be characteristic for ABA-deficiency: a re duced seed dormancy and excessive water loss, leading to a wilty pheno type. Double mutant analysis, combining different aba mutations, indic ated the leaky nature of the mutations.