#colchicine

Plant tissue culture 2

Colchicine is used in plant tissue culture mainly to:

Colchicine is used in plant tissue culture mainly to induce polyploidy and chromosome doubling rather than as fusogen or wall digesting agent. Alkaloid isolated from Colchicum autumnale binds tubulin dimers preventing polymerization into microtubules forming mitotic spindle fibers during metaphase. Without functional spindle, sister chromatids fail to separate at anaphase, nuclear membrane reforms enclosing doubled chromosome complement leading to endoreduplication tetraploid or doubled haploid formation. Application involves treating haploid plantlets derived from androgenesis gynogenesis or

Ref: Blakeslee & Avery 1937 colchicine polyploidy; Dhooghe et al., Plant Methods antimitotic.

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Plant Breeding 4

Colchicine induces polyploidy by inhibiting:

Colchicine, an alkaloid from Colchicum autumnale, binds tubulin dimers and prevents microtubule polymerization essential for spindle fibre formation during mitosis and meiosis. Without functional spindle apparatus formed from microtubules organizing at kinetochores, sister chromatids or homologous chromosomes fail to separate to opposite poles at anaphase; nuclear membrane reforms around doubled chromosome complement. Cell undergoes endoreduplication producing diplochromosome and polyploid nucleus with doubled DNA content. Treatment of meristematic tissue or seedlings with 0.1-0.5% colchicine

Ref: Eigsti OJ & Dustin P. Colchicine in Agriculture – mechanism spindle inhibition. Blakeslee 1937 Science

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Cytoskeleton

Which drug binds tubulin subunits and prevents polymerization?

Microtubule targeting agents divided into destabilizers preventing polymerization and stabilizers blocking depolymerization used as chemotherapeutics and cell biology tools. Nocodazole colchicine and colcemid belong to destabilizer class binding soluble tubulin dimer interface. Nocodazole binds beta tubulin at colchicine adjacent site near intradimer interface distorting dimer curvature preventing straight conformation compatible with lattice addition and reducing lateral contacts. Result reduces effective free tubulin pool shifts equilibrium below critical concentration triggering disassembly

Ref: Jordan & Wilson, Nat Rev Cancer 2004 – Microtubule destabilizers nocodazole binds tubulin prevents polymerization.

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Chromosome variations

Colchicine induces polyploidy by

Colchicine, an alkaloid from Colchicum autumnale, binds to tubulin dimers and blocks microtubule polymerization. Without functional spindle fibers, duplicated chromatids cannot migrate to poles at anaphase, and kinetochore tension fails. Cells exit mitosis with doubled chromosome number in a single restitution nucleus, creating polyploid or C-mitotic cells. In plant breeding, seedling meristems soaked in low colchicine produce tetraploids with larger organs, thicker leaves and increased vigor. Oryzalin and trifluralin act similarly. Effect is specific to spindle disruption, not direct mutagene

Ref: NCBI Bookshelf, Plant Breeding: Polyploid Induction; Griffiths, Chapter 8: Experimental Polyploidy

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