The major difference between the two methods is the number of copies inserted. Gene gun leads to multiple site insertions whereas agro method yields lower copies. Gene gun though universal is expensive. Agro method relies on genotype of explant used..

The major difference between them is that in gene gun there is the chance of tissue damaging but in gene gun there is no chance of damaging. I prefer Agrobacterium gene transformation.

Hi,

As already said by Ashraf, Gene Gun causes damages to the tissue, that can lead to cell death within few days. It is then mainly used for transient expression assays on differentiated cells, in onion epidermal cells for example. It is fast.

It is sometimes used for stable transformation while bombarding immature ovules of reluctant species.

It needs expensive equipment and labware (gold or tunsten beads).

On the other hand Agrobacterium causes few damages and you can adapt the Agro strain to the species/genotype you're trying to transform.

You can use Agro for transient expression in tobacco leaves for example, or on cell suspensions, as well as for stable transformation by meristem co-culture, or ovule transgenesis by floral dipping/spraying.

Agro is much easier to handle, but it needs GMO safety labs and culture rooms, while gene gun requires none.

Thanks for the comments everyone! I know there are more comparisons as well, for example, with gene gun, you can co-bombard various DNAs together at titratable amounts, whereas in agrobacterium transformation, that is not possible. Any other thoughts?

@ Andika,

With gene gun, you can co-bombard different genes. You can also co-transform different genes using Agrobacterium (for example, using different T-DNA cassette in a single strain Agrobacterium). It is possible!!

1. And, obviously, bombardment has no Agrobacterium 'overgrowth' problem, where Agrobacterium grow out of control and kill the explants.

2. To remove Agrobacterium, certain antibiotic need to be used, such as carbenicillin and cefotaxime which are expensive too.

3. Using Agrobacterium, some resilent Agrobacterium can surrive antibiotic selection and carry over to T1, T2 and even later generations. This can generate 'false positive' transgenic lines in molecular screening/analysis (such as PCR).

Great inputs @Yuan-Yeu Yau!

Application difference #1:

In principle, Agrobacterium is mainly used for dicot plant transformation, and biolistics (gene gun) is mainly used for monocot plant transformation, although nowadays, researchers have successfully used Agrobacterium for major monocot crops (such as rice) genetic transformation (through immature embryos). There are still many monocot plants out there. So, if the Agrobacterium-mediated transformation protocol has not yet set up for them, bombardment approach sould be the first choice for their genetic transformation.

Application difference #2:

Both 'Agrobacterum' and 'gene-gun' can be used for gene transient assay. For example, Agroinfitration (inject Agrobacterium into plant tisses) can be done on tobacco leaves to see GFP fluorescent, and bombardment can be done on onion skin to check GUS gene (mentioned above).

However, Agroinfiltration is usually used by researchers if the produced 'recombinant proteins' needed be isolated for further protein assay.

Application difference #3:

There are TWO main plant genetic transformations-- (1) nucleus DNA transformation and (2) plastid (chloroplast) transformation. Plastid transformation is generally used for molecular pharming/farming (produce an recombinant protein (ex. antibody) through plants). For plastid transformation, virtually all transformations are done by bombardment (not Agrobacterium). Naked DNA is shot into cells and insert into plastid genome through homologous recombination.

Application difference #4:

1. 'Linear' DNA, for example, a purified PCR fragment (or a digested restriction fragment) can be directly shoot (by gene gun) into plant cells, without further cloning. On the contrast, PCR fragment has to be cloned into a T-DNA cassette on a binary vector for Agrobacterium-mediated transfomation.

2. Gene gun is able to deliver/shoot 'protein' or 'RNA' moleculars (instead of DNA; wrapped inside a nanoparticle) into plant cells, Agrobacterium cannot do so. Nanoparticle-capsuled Cre protein from site-specific recombination system (Cre-lox) had been shot into plant cells to remove selectable marker gene (flanking by two lox sites).

Application difference #5:

When DNA integrates into cellular genomic DNA, 'double-stranded' DNA (ex. a plasmid) is usually needed. For example, when we do site-specific integrations using site-specific recombination systems (ex. Cre-lox system), we use bombardment or PEG-mediated methods to deliver double-stranded DNA into plant cells. Then site-specific integration can be achieved through recombination between genomic double-stranded loxP and plasmid double-stranded loxP site. We usually don't use Agrobacterium to deliver loxP-containg DNA fragment, because 'T-DNA' is transferred into plant cells single-straned. Although some strategies had been used to successfully use T-DNA to perform site-specific recombination.

The principle practical difference is that Agrobacterium will deliver significantly cleaner events than the gene gun. The gene gun tends to deliver a higher frequency of multiple copy events (this can be mediated by playing with the amount of DNA delivered per shot), but small fragments of DNA also tend to integrate randomly. The upshot of all this, so to speak, is that clean, single copy Agro events tend to express better and more consistently, with less pleiotropic effects (and yield drag, ultimately).

Protocols exist for Agro transformation of most commercial crops, including the major monocots: corn, rice, wheat, sorghum. You may need to empirically determine the appropriate Agro strain and antibiotic to control overgrowth. Timentin, cefotaxime and meropenem are good choices.

Uncontrolled multiple copy inserts happen through particle bombardment while using bacterium as a transfer vector will produce more single copy transgenic events. Moreover, AMT is genotype dependent while PB can deliver T-DNA cassettes in any variety. More reads :)

https://www.ncbi.nlm.nih.gov/m/pubmed/22869288/

https://rd.springer.com/article/10.1007/s00299-004-0892-x