Abstract
BiP is an Hsp70 in the endoplasmic reticulum (ER). Arabidopsis thaliana has three BiP genes, AtBiP1, AtBiP2 and AtBiP3. AtBiP1 and AtBiP2 are ubiquitously expressed under normal growth condition, while AtBiP3 is expressesed only under the ER stress conditions.
Single deletions of each AtBiP gene did not show any obvious phenotype. On the other hand, atbip1 atbip2 double mutant was not obtained, indicating essential and redundant functions of these two AtBiP genes. To investigate functions of AtBiP1 and AtBiP2 in male and female gametophyte, we performed reciprocal cross experiments of atbip1/+ atbip2/atbip2 mutant and found that atbip1 atbip2 double mutation was lethal in the female gametophytes, but not in the male gametophytes. Embryos generated by fertilization of atbip1 atbip2 female gametophyte aborted in development at the early stage of embryogenesis. Interestingly, the wild type AtBiP1 gene from the male gametophytes did not complemt this embryonic lethality.
