PROTEINS ENCODED BY AN AUXIN-REGULATED GENE FAMILY OF TOBACCO SHARE LIMITED BUT SIGNIFICANT HOMOLOGY WITH GLUTATHIONE S-TRANSFERASES AND ONE MEMBER INDEED SHOWS INVITRO GST ACTIVITY

A number of cDNAs corresponding to auxin-regulated mRNAs have been iso lated from tobacco and found to be encoded by a multigene family consi sting of three subfamilies. Homologous proteins have been isolated ind ependently from soybean and potato. Here we report that the encoded pr oteins show a limited but significant homology to both plant and anima l glutathione S-transferases (GST, EC 2.5.1.18). For the protein NT103 , encoded by a member of the Nt103 subfamily, we demonstrate an in vit ro GST activity. This is the first time a function is attributed to a member of this group of auxin-induced proteins or any of its homologue s. The implications of this finding and the possible relationships bet ween auxins and GSTs are discussed.