Increased expression of the maize immunoglobulin binding protein homolog b-70 in three zein regulatory mutants.
Plants carrying floury-2, Defective endosperm-B30, or Mucronate mutations overproduce b-70, a maize homolog of the mammalian immunoglobulin binding protein. During endosperm development in these mutants, levels of both b-70 protein and RNA increase dramatically between 14 days and 20 days after pollination. At later stages, b-70 RNA levels decline while protein levels remain high. The increase in b-70 RNA levels is endosperm specific and dependent on gene dosage in the floury-2 mutant. In all three mutants, the increases in b-70 RNA and protein levels are inversely proportional to changes in zein synthesis. Although b-70 polypeptides can be extracted from purified protein bodies, they carry a carboxy-terminal endoplasmic reticulum retention signal, HDEL. We propose that induction of b-70 in these mutants is a cellular response to abnormally folded or improperly assembled storage proteins and probably reflects its role as a polypeptide chain binding protein.
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Department of Botany, North Carolina State University, Raleigh 27695-7612.
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D029681:Arabidopsis Proteins; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D000091342:Endoplasmic Reticulum Chaperone BiP; D005786:Gene Expression Regulation; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D018832:Molecular Chaperones; D009154:Mutation; D009928:Organ Specificity / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics; D012639:Seeds / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D017385:Sequence Homology; D003313:Zea mays / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D015028:Zein / Q000235:genetics
D029681:Arabidopsis Proteins; D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D010940:Plant Proteins; D012333:RNA, Messenger; C077221:BIP protein, Arabidopsis; D015028:Zein