GASA, A GIBBERELLIN-REGULATED GENE FAMILY FROM ARABIDOPSIS-THALIANA RELATED TO THE TOMATO GAST1 GENE

A multiple gene family of at least four members, related to a GA-stimu lated transcript (GAST1) from tomato, was characterized in Arabidopsis thaliana by analysing four related cDNAs, named GASA1 to GASA4. The c orresponding peptides display comparable structural features: (1) a pu tative signal peptide of 18 to 23 residues; (2) a highly divergent hyd rophilic region of about 22 amino acids; (3) a conservative 60 amino a cid C-terminal domain containing 12 cysteines. This organization has a lso bean shown in two related peptides from tomato, GAST1 found in sho ots and RSI-1 found in early lateral roots. Southern blot hybridizatio n patterns showed single-copy genes for all four members of the GASA f amily. Accumulation of the various transcripts, monitored by northern blot hybridization, indicated that the various genes are expressed dif ferentially in plant organs: Specific mRNAs were mostly detected in fl ower buds and immature siliques in the case of GASA1, in siliques and dry seeds in the case of GASA2 and 3, and in growing roots and flower buds in the case of GASA4. At least two of the GASA genes are activate d in GA-deficient mutant ga5, as early as 4 to 8 h after spraying with 50 mu M GA(3). The complex patterns of expression and regulation of t he various genes suggest that the related peptides are involved in a d evelopmental regulation process in Arabidopsis.