Mutations in the ULTRACURVATA2 gene of Arabidopsis thaliana, which encodesa FKBP-like protein, cause dwarfism, leaf epinasty and helical rotation ofseveral organs

Contrary to wild-type Arabidopsis thaliana vegetative leaves, which are fla ttened organs, those of ultracurvata (ucu) mutants are spirally rolled down wards and show reduced expansion along the proximodistal axis. We have iden tified six ucu lines, whose genetic analysis indicates that they fall into two complementation groups, UCU1 and UCU2. Here we describe three recessive ucu2 alleles, whose homozygotes are dwarf with a compact rosette, and disp lay some organs that are helically rotated along the apical-basal axis, a t rait that is more pronounced in roots, pistils and mature siliques. Followi ng a map-based strategy, we have identified the UCU2 gene, which was found to encode a peptidyl-prolyl cis-trans isomerase of the FKBP (FK506-binding protein) family of proteins.