The ER chaperone calreticulin plays vital roles in numerous cellular processes, including Ca2+-homeostasis, apoptosis and cell adhesion, in animal cells. Although calreticulin has been systematically characterized in animal cells, the focus has been on one of the isoforms. However, recent advances in the plant calreticulin field have revealed functional divergence of calreticulin isoforms. While two of the plant isoforms appear to work within a general ER chaperone framework, the third isoform is associated with folding of receptors for brassinosteroids and bacterial peptides. Hence, the discovery of functional specialization of plant calreticulins opens up new vistas for calreticulins also in the animal field.