Moving Genes

Gene transfer is common place in our world.  When a baby is born there is DNA from both the mom and dad that made a unique human.  When the wind blows pollen from one plant to another there are new genes genes being incorporated with the outcome of a seed.  That seed and resulting plant will be different from its parent plants.  This is nothing new and we all know the basics of the birds and the bees.  Plant breeders do this for a living. By the simple means of  manually moving pollen from one plant to another they have turned the food crops into what they are today.

Most people are at ease with this process or at least take it for granted.  More unease comes when we take a gene from one organism and move it to another.  For example when we take a gene from bacteria (Bt) and move it into soybean.     I have talked in a past about agrobacterium which is a bacteria that transfers its DNA into another organism's genome (grapes, trees, shrubs, etc.) in order to form a crown gall or tumor.   There is  a study that shows that the sweet potatoes we eat today have genes from this bacteria.  So even in nature there is a mechanism by which genes are transferring from one organism to another and STAYING there from generation to generation.

The question really becomes how common is gene transfer from one organism to another in nature.  It may be more common than we though.  Another paper has come out that details the relationship of caterpillars and parasitic wasps.

In college I did a lot of research on tobacco and I remember seeing the tobacco hornworm for the first time.  What is that thing!   They get huge and will "click" at you when they get mad.  Then I remember seeing the the first horn worm with white things sticking all over it.  The guys in the field explained that a wasp comes, paralyzes the insect for a short amount of time,  and lays its eggs in the insect.   The larvae use the insect to feed and grow, usually killing it and then hatch out.  Wow. 
And kinda gross.  Just Google images of parasitic wasp and see what they can do insects. You might want to not have eaten yet though.

http://spalbert.wpengine.com/2012/06/parasitic-wasps-beneficial-insects/parasitic-wasp-eggs-on-hornworm/

The crazy thing is that when the wasp injects its eggs it also injects a virus called bracovirus.  Normally if you get a splinter in your finger your body knows something is not right and mounts an immune response to try to get it out or take care of it.  The caterpillars have mechanisms to mount their own immune response for something like an alien growing inside of them, but the bracovirus specializes in keeping the caterpillar from mounting that immune response so the wasp's eggs can grow and not be affected.  These wasps are pretty smart!

That brings us to the climax of the story.  When scientists have looked at the genome of these caterpillars they found genes in the caterpillars from the bracovirus.   In some cases when the caterpillar did not die, some of the virus genome was incorporated into the caterpillar genome and has been passed down from generation to generation.  The more astounding fact is that sometimes the virus picked up wasp genes and then once the virus passed into the caterpillar, they picked up both wasp genes and virus genes. 

What does this even mean?  The scientists found that the genes from the bracoviurs that are active and have been incorporated in the caterpillar actually inhibit another virus called baculovirus.  So the caterpillar still can have a nasty death from parasitic wasps.   But the silver lining is that through the generations they have become Genetically Modified Organisms (without any human help) with genes from other species and these genes actually help them against another pathogen.  It truly is a transgenic world.


Sources:

http://news.sciencemag.org/biology/2015/09/wasps-have-injected-new-genes-butterflies