In the wake of "Cinematic Corn: Oz, Twister, Signs, Interstellar, and More," here are some additional thoughts on the meaning behind the use of "corn" in films.
Osiris is the Ancient Egyptian Lord of the Dead, King of the Underworld, who was killed by His brother Seth and restored to life by Isis and Anubis. He was associated with the sprouting corn of springtime. ~ Thalia Took, A-Muse-ing Grace Gallery
At the beginning of the Dances With Wolves, Dunbar appears as "a Christ figure and sacrificial lamb" with the Confederate side's cornfield in the background. ~ Roderick Heath, Source.
Because Osiris is the Corn God = Christ on the cross = the scarecrow on the cross, etc. Thus, corn represents death and rebirth.
The ancient Egyptian's regarded their god Osiris as a corn god. For them, the death and rebirth of the god was personified in the annual growth cycle of the corn crops....
...Osiris was a corn god. This brings us to the famous Egyptian myth of Osiris, Set, and Isis.
In short, Osiris' brother Set seals him in a coffin until he suffocates (note: he can't breathe) then throws the coffin in the Nile River. Osiris' wife Isis eventually finds the coffin where it landed in a tree and resurrects him, but then Set kills him again by chopping him up into pieces.
~ Sibyl Hunter, Source.
Inception: ...Mal wants to trap her husband Dom Cobb (Osiris, the Corn God of the Underworld, played by Leonardo DiCaprio) [Cobb, name game = corn = Osiris] in the dream world of the unconscious.
My corn I take seriously, because it's mine. And my potatoes and tomatoes and my fence I take note of because they're mine. But this war is not mine and I don't take note of it. ~ Charlie Anderson, played by James Stewart in Shenandoah (1965)
In Interstellar, the Cooper family eats meals consisting of all-corn dishes. But then, as Sibyl Hunter notes, it is almost sacrilegious when the adult Murphy burns the corn fields at the end of the movie. A rejection of the ancient Earth to move on to the Heavens?