GENE ISOLATION IN ARABIDOPSIS-THALIANA BY CONDITIONAL OVEREXPRESSION OF CDNAS TOXIC TO SACCHAROMYCES-CEREVISIAE - IDENTIFICATION OF A NOVELEARLY RESPONSE ZINC-FINGER GENE

In an effort to identify novel regulatory plant genes, conditional ove rexpression of toxic Arabidopsis thaliana gene products in Saccharomyc es cerevisiae was evaluated as a genetic selection scheme. The screeni ng method was tested on a fraction of a cDNA expression library and le d to the identification of two Arabidopsis cDNA clones that were toxic to yeast; one corresponded to histone H1 and the other to a previousl y unidentified gene. This new gene, named ATL2, combines a RING-like z inc-binding motif and a putative signal anchor sequence for membrane i nsertion in the same molecule. Furthermore, inspection of the 3' untra nslated region reveals two types of sequences which appear to be key d eterminants in rapid transcript decay. Indeed, rapid and transient acc umulation of transcript occurs in the presence of a protein synthesis inhibitor and of the growth regulator auxin. These features provide ev idence that ATL2 is an early-response gene. Thus, ATL2 represents one of the first early-response plant genes to be described which possesse s a distinct regulatory domain; the fact that ATL2 mRNA is induced by auxin suggests that it might have a role during the response of plants to this growth regulator.