Like in many domesticated species, the fibrous seed covers, known as glumes, that protect corn kernels from the elements or herbivores have been dramatically reduced to allow easier access and digestibility.  Varieties of corn that carry one or a series of mutations that partially or wholly restore these kernel covers are known as pod corn.  Notably, at a time when there was a big debate over the identity of corn’s wild ancestor, these varieties were raised as a possible example of an extinct wild corn species that cultivated corn may have replaced (We now know the living wild plant teostinte is the ancestor). 

Two recent studies have identified the mutation, tunicate-1, that makes the makes the pod corn kernels not so naked.  Surprisingly, the initial causal genomic change was a 1.8 Megabase chromosomal inversion.  By flipping DNA around in the corn genome, this rearrangement moved a key regulatory gene and placed it near a new non-coding promoter DNA element, causing the gene to be misexpressed in a new tissue in the developing corn ear and thus leading to restoration of partial glume formation.  Subsequent duplications of this gene in the inverted region increased the gene’s expression dosage and thus promoted full-sheathed kernels. 

--Ben Blackman