The Role of Plastids in the Expression of Nuclear Genes for Thylakoid Proteins Studied with Chimeric [beta]-Glucuronidase Gene Fusions.

AUTOR(ES)

Bolle, C.

RESUMO

We have analyzed plastid and nuclear gene expression in tobacco seedlings using the carotenoid biosynthesis inhibitor nor-flurazon. mRNA levels for three nuclear-encoded chlorophyll-binding proteins of photosystem I and photosystem II (CAB I and II and the CP 24 apoprotein) are no longer detectable in photobleached seedlings, whereas those for other components of the thylakoid membrane (the 33- and 23-kD polypeptides and Rieske Fe/S polypeptide) accumulate to some extent. Transgenic tobacco seedlings with promoter fusions from genes for thylakoid membrane proteins exhibit a similar expression behavior: a CAB-[beta]-glucuronidase (GUS) gene fusion is not expressed in herbicide-treated seedlings, whereas PC-, FNR-, PSAF-, and ATPC-promoter fusions are expressed, although at reduced levels. All identified segments in nuclear promoters analyzed that have been shown to respond to light also respond to photodamage to the plastids. Thus, the regulatory signal pathways either merge prior to gene regulation or interact with closely neighboring cis elements. These results indicate that plastids control nuclear gene expression via different and gene-specific cis-regulatory elements and that CAB gene expression is different from the expression of the other genes tested. Finally, a plastid-directing import sequence from the maize Waxy gene is capable of directing the GUS protein into the photodamaged organelle. Therefore, plastid import seems to be functional in photobleached organelles.

Documentos Relacionados

• In vivo analysis of Chlamydomonas chloroplast petD gene expression using stable transformation of beta-glucuronidase translational fusions.
• Gene fusions of signal sequences with a modified beta-glucuronidase gene results in retention of the beta-glucuronidase protein in the secretory pathway/plasma membrane.
• In vivo random beta-glucuronidase gene fusions in Arabidopsis thaliana.
• Rice Triosephosphate Isomerase Gene 5[prime] Sequence Directs [beta]-Glucuronidase Activity in Transgenic Tobacco but Requires an Intron for Expression in Rice.
• Expression of the Escherichia coli beta-glucuronidase gene in Pseudocercosporella herpotrichoides.