The role of PASTICCINO1, an FKBP-like protein, in plant development

Abstract

The pasticcino (pas) mutants of Arabidopsis thaliana were identified due to their abnormal response to cytokinins. These mutants fall into 3 complementation groups: pas1 (2 alleles), pas2 (1 allele) and pas3 (4 alleles). The mutants all have excessive and disorganised cell divisions leading to extra cell layers in the hypocotyl, abnormal apical meristems, and rosettes with fused vitreous leaves. This cell proliferation effect is exaggerated in the presence of cytokinins. The PAS1 gene was cloned via a T-DNA insertion; it encodes for a protein with similarities to FK506-binding proteins (FKBPs), a class of immunophilins. Like other large FKBPs the PAS1 protein has several putative FKBP domains, a tetratricopeptide repeat domain and a calmodulin binding motif. PAS1 also has conserved nuclear localisation signals. Although the presence of immunophilins has been demonstrated in plants, their functions are unknown. PAS1 is the first plant immunophilin-like gene to be disrupted and suggests a role for PAS 1 in the control of plant cell division.