Overexpression of the wheat FK506-binding protein 73 (FKBP73) and the heat-induced wheat FKBP77 in transgenic wheat reveals different functions of the two isoforms.

The FK506-binding proteins (FKBPs) belong to the peptidyl prolyl cis-trans isomerase (PPIase) family, and catalyse the rotation of the peptide bond preceding a proline. They are conserved in organisms from bacteria to man. In order to understand the function of plant FKBP isoforms, we have produced transgenic wheat plants overexpressing each of the two wheat FKBPs: wFKBP73 (which is expressed in young vegetative and reproductive tissues under normal growth conditions) and wFKBP77 (which is induced by heat stress).

Deletion of the C-terminal 138 amino acids of the wheat FKBP73 abrogates calmodulin binding, dimerization and male fertility in transgenic rice.

Wheat FKBP73 (wFKBP73) belongs to the FK506-binding protein (FKBP) family which, in common with the cyclophilin and parvulin families, possesses peptidyl prolyl cis-trans isomerase (PPIase) activity. Wheat FKBP73 has been shown to contain three FKBP12-like domains, a tetratricopeptide repeat (TPR) via which it binds heat shock protein 90 and a calmodulin-binding domain (CaMbd). In this study we investigated: (1) the contribution of the N-terminal and C-terminal moieties of wFKBP73 to its biological activity by over-expression of the prolyl isomerase domains in transgenic rice, and (2) the biochemical characteristics of the C-terminal moiety.