As AtBiP1 and AtBiP2 have been shown to be functionally redundant in Arabidopsis (Maruyama et al., 2010) and, given that in the individual bip1 and bip2 mutant lines CMV infection was unaffected, these findings offer further support for the hypothesis that both AtBiP1 and AtBiP2 are present within the PD ER (Fig. 1D, E). This evidence concerns the gene BIK and cytomegalovirus infection.