Abstract
Microtubules are widely conserved structure in eukaryotes and have essential roles for various cell activities. In plant cells, microtubules are known to control cell elongation and have great influence on plant shape. It has been suggested that alignment of cortical microtubule bundles in expanding interphase cells determine the direction of cell elongation by the proper regulation of microtubule-associated proteins. However, how cortical microtubules are nucleated and become progressively organized has not been well understood. Our previous screening identified PROPYZAMIDE HYPERSENSITIVE1 (PHS1). PHS1 encodes a MAP kinase phosphatase which is preferentially expressed in elongating cells. When a phosphatase-inactive-form PHS1 was expressed in Arabidopsis plants, cells at the elongation zone swelled and root growth was strongly inhibited. In addition, cortical microtubule arrays are strongly depolymerized by transient expression of inactive-form PHS1. Therefore cortical microtubule arrays are possibly regulated by phosphorylation pathway. Thus we are now trying to understand the pathway in detail.
