(A) Set of eight ORK genes (OPPOSITELY REGULATED BY REVOLUTA AND KANADI). (B) Structure of the ABIG1 gene. HD - DNA binding homeodomain, ZIP-leucine zipper responsible for homodimerization, EAR – domain responsible for interaction with TOPLESS family co-repressors, CPSCER – conserved domain of unknown function. Arrows - position of PCR primers for ABIG1 Q-RTPCR in panels C-E. Position of gene trap insertion is shown. The sequence above indicates junction between ABIG1 gene and DS insertion (italics). (C) ABIG1 mRNA in wild type and abig1-1 homozygous mutant plants in response to ABA treatment (whole plants grown in liquid media). **p<0.01. (D) ABIG1 mRNA in wild type and abscisic acid insensitive (abi1-1) mutant plants in response to ABA treatment (whole plants grown in liquid media). Letters indicate pairs showing significant differences (p<0.05; t-test). (E) ABIG1 mRNA in response to drought treatment. Water was withheld from rosette stage plants beginning on day one. RNA is from stems and leaves of plants grown in soil. Asterisk indicates time points where watered and unwatered plants differ significantly (p<0.05; t test). (In all cases, bars indicate ± s.e.m. for three biological replicates. The data in each graph are from independent experiments.) (F). Increase in extent of GUS expression in abig-1/+ plants treated with ABA. (G) GUS expression from GT7363 genetrap in abig1-1/ + plant. White line points to area of expression at basal petiole and subtending the shoot apex. (H) Longitudinal thin section through abig1-1/+ seedling showing GUS expression along vascular strands. SAM – shoot apical meristem and associated young leaf primordia; vp – vascular parenchyma; te – tracheary elements; p – petiole. (I) Cross section through a leaf petiole of an abig1-1/+ seedling showing GUS expression in vascular parenchyma cells associated with tracheary elements of xylem. (J) GUS stained hypocotyl/root junction of abig1-1/+ seedling. (K) GUS stained hypocotyl/root junction of abig1-1/+ seedling treated with ABA for three hours. (L) GUS stained hypocotyl/root junction of abig1-1/abig1-1 seedling. (M) GUS stained hypocotyl/root junction of abig1-1/abig1-1 seedling treated with ABA for three hours.