Os02g0115900

The rice Os02g0115900 was reported as BiP in 2009 by researchers from Japan.

Annotated Information

Gene Symbol

• Os02g0115900 <=> OsBiP1, BiP1, BiP, Bip3, OsBiP3, BIP1/OsBIP3, OsMed37_2, Med37_2

Function

• Seed storage proteins are specifi cally and highly synthesized during seed maturation and are deposited into protein bodies (PBs) via the endoplasmic reticulum (ER) lumen.
• The accumulation process is mediated by ER chaperones such as luminal binding protein (BiP) and protein disulfi de isomerase (PDI)
• The PB-like structure (BiP) may be formed in the ER lumen, resulting in inhibition of translation, folding and transport of seed proteins.
• BiP interacts with nascent immature secretory proteins synthesized from membrane-bound polysomes on the ER,and assists in protein folding in concert with other chaperones and folding helpers such as calnexin and protein disulfide isomerase-like proteins in the ER lumen.
• BiP not only participates in assistence of protein folding but also take part in the protein degradation process known as ER-associated degradation.

Phenotypic analysis

• The seed phenotype of the PDI-overexpressing transformant was almost identical to that of the wild type, whereas overexpression of BiP resulted in transgenic rice seed that displayed an opaque phenotype with fl oury and shrunken features.
• In the BiP-overexpressing line, the levels of accumulation of seed storage proteins and starch contents were signifi cantly lower compared with the wild type.
• Interestingly, overproduction of BiP in the endosperm of the transformant not only altered the morphological structure of ER-derived PB-I, but also generated unusual new PB-like structures composed of a high electron density matrix containing glutelin and BiP and a low electron density matrix containing prolamins.
• Notably, polysomes were attached around the aberrant PB-like structures, indicating that this aberrant structure is an ER-derived PB-I derivative.

Evolution

• BiP is one of the major ER chaperones and belongs to the heat shock protein 70 (HSP70) family.Rice BiP3 (OsBiP3) shows the greatest similarity to ArabidopsisBiP1 and BiP2 with 89.2% and 89.3% identity.
• BiP with an ATPase domain at its N-terminus and a protein-binding domain at its C-terminus allows BiP to cycle between ATP hydrolysis and ADP exchange, and it is coupled to binding and release of the unfolded protein.
• BiP protein has a KDEL ER retention signal at the C-terminus and is retained in the ER lumen.

Labs working on this gene

• Transgenic Crop Research and Development Center, National Institute of Agrobiological Sciences, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602 Japan
• Research Team for Crop Cold Tolerance, National Agricultural Research Center for Hokkaido region, Hitsujigaoka 1, Toyohira-ku, Sapporo,Hokkaido, 062-8555 Japan
• Rice Biotechnology Research Team, National Institute of Crop Sciences, Kannondai 2-1-18, Tsukuba, Ibaraki, 305-8518 Japan