DIFFERENTIAL REGULATION OF 1-AMINOCYCLOPROPANE-1-CARBOXYLATE SYNTHASEGENE FAMILY AND ITS ROLE IN PHENOTYPIC PLASTICITY IN STELLARIA LONGIPES

Using degenerate oligonucleotides that correspond to conserved amino a cid residues of known 1-aminocyclopropane-1-carboxylic acid (ACC) synt hases, we cloned a genomic fragment that encodes ACC synthase in Stell aria longipes. Southern analysis suggests that ACC synthase is encoded by a small gene family comprising about 4 members. We isolated four u nique ACC synthase cDNA clones under different growth conditions from alpine and prairie ecotypes of S. longipes. Northern analyses suggest that ACC synthase genes are differentially and synergistically regulat ed by photoperiod and temperature. Such differential regulation of ACC synthase genes positively correlate with the levels of ACC and ethyle ne. Since ethylene has previously been shown to partly control the ste m elongation plasticity in S. longipes, we propose that differential r egulation of ACC synthase genes may represent one of the underlying mo lecular mechanisms of phenotypic plasticity in S. longipes.