Curious as to what CorA1 is and what it does?
You see, CorA and CorA1 are two different things. CorA is a protein, while CorA1 is the gene that codes for that protein.

It is the genes that when translated give rise to the protein.

This gene was isolated from the Rhizobium meliloti, a bacterium commonly known for forming leguminous nodules in certain plants. 

As for it's function, I'm not really a biologist, but I know that magnesium is a component of chlorophyll (It's coordinated at the center of the porphyrin complexes).



So you could say magnesium is rather important for plants. The $\ce{Mg^2+}$ ion needs to be transported from the soil to the leaves, and this protein facilitates this transport.