Re infectivity of naked viral DNA

[Patrick O'Neil]

On 17 May 1995, Ulrich Melcher wrote:

> However, I know that naked DNA is infectious in at least some
> situations.  We have for years been extracting the circular
> double-stranded DNA from cauliflower mosaic virus, mixing it
> with a little abrasive and rubbing it on the leaves of turnip
> plants.
[...]

I have heard of this method...and am wondering what else is involved. 
What are the abrasive beads mixed with (solution)?  Perhaps some
cellulase?  Also, this is still not in conflict with my original post
about it:  in this procedure, cells walls are disrupted as are, perhaps
(and to a much lessor extent) cell membranes.  The rubbing would then act
to work polynuc into the interior of the cell, allowing transcription from
those that are not sheared into fragments.  This is not the same as
exposing completely intact plant cells to polynucs and waiting for action. 
A normal cell is set up/evolved to avoid invasion by outside polynucs 
because under most circumstances, foreign DNA/RNA means infection.  As it 
goes, special manipulations or treatments must be used to get past 
natural barriers to invasion, such as chemical solutions, etc, to disrupt 
cell walls and membranes which THEN allows easy entry for polynucs.  

Try the same plant experiment: no abrasive, no rubbing.  Just add a drop 
of TE plus viral DNA or RNA and watch for infection.  Another test would 
be to add the same polynuc into liquid solution for growing seedlings and 
see if the resulting plants end up with infection of appropriate virus.  


I do apologize if I come across too dogmatically, but I require strong 
evidence to indicate that naked DNA or RNA and NO SPECIAL MANIPULATIONS 
can produce anything but free nucleotides as a result of degredation.
As it is, I will be picking up the references cited here to see if any of 
them address the specifics of my objection or if they involve special 
manipulations or solutions rather than simple "exposure."

Patrick