You see, there's a little problem there.
Right, I can see that would be a bit of a problem. Instead of oxygen, grass that produces cyanide gas. Wow, that would be a problem.
Imagine stuff like this spreading as far as toxic colon-eating GM Star Corn. Infecting all the grasslands of the planet. Step outside for a whiff of that old fresh mown hay and get a deep breath of cyanide gas.
That could be a problem.
GM is so insane, it is beyond insanity. There are insane people standing around going "Gosh, that GM stuff is crazy."