Abstract
The propyzamide hypersensitive1-1 (phs1-1), semi-dominant Arabidopsis mutant, roots show left-handed helical growth phenotype when grown on hard agar plates. In the presence of 3μM propyzamide, a microtubule (MT) destabilizing drug, the root epidermal cells swell radially and are hyper-sensitive to this and other MT destabilizing drugs. The cortical MTs of phs1-1 root epidermal cells are shorter, and less well organized (with a tendency to form right-handed helices) than wild-type MTs. We identified the PHS1 gene by a map-based cloning approach. The C-terminus of PHS1 protein has a dual-specificity protein tyrosine phosphatase (DsPTP) catalytic domain. PHS1 was fused with glutathione-S-transferase, overexpresed in E. coli, and purified. PHS1 fusion protein dephosphorylated at a artificial substrate. The phs1-2 allele in which PHS1 gene was disrupted by T-DNA was recessive embryo-lethal. Analysis of transgenic plants expressing PHS1 genome regions indicated that phs1-1 R64C mutation is dominant-negative.
