Accumulation of maize γ-zein and γ-zein: KDEL to high levels in tobacco leaves and differential increase of BiP synthesis in transformants |
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Authors: | M Bellucci A Alpini F Paolocci L Cong S Arcioni |
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Institution: | (1) Istituto di Ricerche sul Miglioramento Genetico delle Piante Foraggere, CNR, via Madonna Alta 130, 06128, Perugia, Italy e-mail: s.arcioni@irmgpf.pg.cnr.it Tel.: +39-075-5005217, Fax: +39-075-5005228, Present address: L. Cong, Institute of Animal Science, CAAS, Yuanming Yuan West Road 2, Haidian, 100094, Beijing, China, IT |
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Abstract: | Two gene constructs (pROK.TG1L and pROK.TG1LK) were utilized to achieve accumulation of maize γ-zein to high levels in tobacco
(Nicotiana tabacum L.) leaves. Both the chimaeric genes contained the γ-zein-coding region preceded by the 5′untranslated leader from the coat
protein mRNA of TMV, but one of them (pROK.TG1LK) was modified in its protein-coding region by the addition of the ER retention
signal KDEL. The accumulation of γ-zein and γ-zein:KDEL in leaves was compared with heterologous protein accumulation in tobacco
plants previously transformed with a γ-zein cDNA harbouring a native 5′UTR. Replacement of γ-zein 5′UTR with the TMV leader
dramatically increased γ-zein production. Furthermore, γ-zein:KDEL-expressing plants, on average, accumulated twice as much
foreign protein in their leaves as pROK.TG1L plants. The two-fold increase in the level of γ-zein:KDEL can probably be attributed
to an improvement in the mechanism for ER retention of zeins in the transgenic cells. Transformants also showed increased
production of BiP, though to a lesser extent in γ-zein:KDEL-expressing plants compared with pROK.TG1L plants. It is therefore
likely that γ-zein:KDEL retention is made less dependent on the chaperone assistance of BiP by the presence of the KDEL signal
on the γ-zein mutant.
Received: 15 October 1999 / Accepted: 28 February 2000 |
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Keywords: | Gene expression KDEL Nicotiana Transgenic plants γ -Zein |
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