Oryzalin-Induced Microtubule Disassembly and Recovery in Regenerating Protoplasts of the Alga Mougeotia

Abstract

Summary Cortical microtubules in newly formed protoplasts of the alga Mougeotia undergo rapid organization to form symmetrical arrays centered upon two cortical foci. This process is critical to protoplast regeneration because the orientation of the two foci indirectly establishes the future axis of elongation of the protoplasts. To investigate the extent of cellular control of microtubule organization, we employed the anti-microtubule herbicide oryzalin. Depolymerization and recovery of microtubules in 0–4 h old protoplasts was monitored by immunofluorescence microscopy with anti-tubulin. Data are presented on the effect of varying oryzalin concentration and treatment time, and on the rate of microtubule depolymerization. Organized microtubule arrays, including the cortical foci, were as susceptible to oryzalin as unorganized arrays. During recovery, microtubules repolymerized in clusters in contact with the plasma membrane throughout the cortex. Microtubules assembled into transient, locally-ordered arrays prior to the appearance of arrays indistinguishable from those in untreated protoplasts. The process of microtubule organization proceeded from the stage reached before oryzalin treatment, indicating that the protoplasts retained information about the degree of microtubule organization achieved prior to treatment despite temporary loss of microtubules.