Hypothetical model of genetic regulation of the glutelin biosynthesis pathway
2003
Takemoto, Y. | Ogawa, M. | Kumamaru, T. | Okita, T.W. | Satoh, H.
To study the genetic regulation of the glutelin biosynthesis pathway, we induced the highly accumulated 57-kDa glutelin precursor mutant (57H mutant) and characterized four 57H mutants, esp2, Glup1, glup2, and glup3. Electron-microscopic observation showed that glutelin precursor in esp2, Glup1, and glup2 was deposited in the mutant-type protein body (PB) derived from the endoplasmic reticulum (ER). Glutelin precursor and prolamin were mixed in the mutant-type PB, protein in both Glup1 and glup2 was distributed separately in the PB. The glutelin precursors in glup3 were deposited in the PBII with mature glutelin subunits. Glutelin extraction under several conditions indicates that the glutelin precursor and prolamin polypeptides aggregate by an interchain S-S bond in esp2. Western blot analysis demonstrated that esp2 contained BiP and a calnexin, but lacked protein disulfide isomerase (PDI). In esp2, the absence of PDI was considered to have caused glutelin precursor retention in the ER by an irregular S-S bond with prolamin polypeptides. A partial cDNA clone of PDI was isolated and sequenced. The PDI clone possessed a thioledoxin site and ER retention signal, KEDL, at the C-terminal. A comparison of deduced amino acid sequences of PDIs from maize, wheat, and barley showed a shared identity of 84.2% to 84.9%. We constructed a hypothetical model of genetic regulation of the glutelin biosynthesis pathway. The Esp2 gene regulated the expression of PDI, which played an essential role in segregating the glutelin precursor and prolamin polypeptides in the ER. The glup1 and Glup2 genes possibly controlled the transportation from the ER to the vacuole. The Glup3 gene regulated the cleavage of the gluten precursor in the vacuole.
اظهر المزيد [+] اقل [-]الكلمات المفتاحية الخاصة بالمكنز الزراعي (أجروفوك)
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