Abstract
Binding protein (BiP) is one of the most important key chaperons for protein folding in endoplasmic reticulum (ER) lumen. Increasing of mis-folded or incorrectly translated proteins in ER promptly induces BiP gene expression as unfold protein response (UPR). To investigate the role of BiP during rice seed maturation, we generated transgenic rice plants in which the rice BiP gene (AK065743) was overexpressed or suppressed in a seed specific manner. Both seeds of BiP-overexpression and suppression lines displayed a chalky phenotype as flowly and shurunken feature. Furthermore, protein sorting and accumulation systems significantly perturbed in their endosperm cells. RT-PCR analyses indicated that many chaperone genes, other BiP, HSP70, calnexin, Calreticulin and PDI genes, were increased their expression in both of transgenic seeds. These results suggested that transgenic rice seeds with either much higher or lower expression of BiP have caused ER stress in their endosperm cells. Furthermore, immuno-blot analyses of the transgenic rice seed suggested that changes of BiP level significantly affects a quality control system in endosperm cells.
