Spindle sensitivity to isopropyl-N-phenyl-carbamate and griseofulvin of common wheat plants carrying different doses of the Ph1 gene

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Abstract
Lines of common wheat cv. Chinese Spring carrying different doses of the Ph1 gene, located on the long arm of chromosome 5B were treated with the antimitotic agents griseofulvin and isopropyl-N-phenyl-carbamate (IPC). Treatments with low griseofulvin concentrations and IPC resulted mainly in the production of a high percentage of cells exhibiting spindle disorganization at metaphase and multipolar cells at anaphase-telophase. These treatments did not differentially affect the tested genotypes. Higher griseofulvin concentrations induced the appearance of frequent C-metaphases and C-anaphases because of complete disruption of the spindle microtubules: in such cases, more pronounced sensitivity was observed in a line lacking the Ph1 gene than in lines disomic and tetrasomic for chromosome 5B. Subcellular structures regulating microtubule organization and orientation, which are apparently the target of IPC and low griseofulvin concentrations, are apparently not related to the action of the Ph1 gene. Tubulin-microtubules equilibrium, which is affected by colchicine and high griseofulvin concentrations, is influenced by the action of this gene. The Ph1 gene product may correspond to a tubulin or a microtubule-associated protein which in turn stabilizes microtubule structure. The equilibrium tubulin-microtubules would be shifted towards microtubules in plants containing 2 doses of Ph1 and even more in plants containing an extra dose of this gene.