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#fusogen

2 public questions tagged with this topic.

Plant tissue culture 2

Which of the following is NOT a fusogen?

Colchicine is not considered fusogen, unlike true fusogenic agents that promote membrane merging of protoplasts. Legitimate fusogens include polyethylene glycol PEG high molecular weight polymer that dehydrates membrane interface creating calcium bridges neutralizing negative charge inducing lipid mixing upon dilution, high concentration calcium ions at alkaline pH around 10.5 similar mechanism reducing electrostatic repulsion, and inactivated Sendai virus bearing fusogenic HN and F glycoproteins that merge animal and plant membranes albeit rarely used now due to biohazard handling. Electrical pulses via electrofusion also physically fuse membranes through reversible dielectric breakdown not chemical fusogen definition but effective. Colchicine mechanism distinct: it binds tubulin dimer with high affinity blocking microtubule assembly disrupting spindle formation during mitosis leading to polyploidy chromosome doubling, classified as antimitotic alkaloid rather than membrane fusogen. It does not destabilize lipid bilayer nor create intermembrane coalescence step necessary for protoplast fusion. Hence in lists evaluating fusogenic compounds colchicine stands out as non fusogenic used for ploidy manipulation rather than heterokaryon formation, correctly identified as answer for which is NOT fusogen.

Ref: Anne & Harada 1991 fusogens list; Kao 1977 colchicine not fusogen.

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Plant tissue culture 2

Common fusogen used for induced protoplast fusion is:

Common chemical fusogen employed to induce protoplast fusion is polyethylene glycol PEG polymer with molecular weight typically 1500 to 6000 daltons applied at concentration 15 to 40 percent weight per volume combined with calcium ions 50 millimolar and alkaline pH 9 to 10. PEG induces fusion through multiple mechanisms: it is highly hydrophilic binding water molecules dehydrating intermembrane space reducing hydration repulsion between negatively charged phospholipid bilayers, promotes close apposition of membranes via calcium bridging between phosphate head groups and creates molecular disorder increasing membrane fluidity and probability of lipid mixing and coalescence upon gradual dilution washing out PEG. Efficiency of heterokaryon formation ranges 10 to 30 percent depending on species and concentration exposure time 15 to 30 minutes. Although PEG causes some cytotoxicity protein denaturation requiring thorough washing after treatment, it remains cheapest most accessible method for somatic hybridization compared to electrofusion equipment requiring electroporators. Other chemical fusogens include high calcium alkaline pH alone and inactivated Sendai virus with fusogenic hemagglutinin proteins. PEG fusion nonspecifically generates multinucleate products but selection via fluorescence markers or complementation enables recovery of desired hybrids for crop improvement.

Ref: Kao & Michayluk 1974 PEG fusion; NCBI protoplast fusion review.

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