Evolution of the C4 phosphoenolpyruvate carboxylase promoter of the C4 species Flaveria trinervia: the role of the proximal promoter region.
BACKGROUND
The key enzymes of photosynthetic carbon assimilation in C4 plants have evolved independently several times from C3 isoforms that were present in the C3 ancestral species. The C4 isoform of phosphoenolpyruvate carboxylase (PEPC), the primary CO2-fixing enzyme of the C4 cycle, is specifically expressed at high levels in mesophyll cells of the leaves of C4 species. We are interested in understanding the molecular changes that are responsible for the evolution of this C4-characteristic PEPC expression pattern, and we are using the genus Flaveria (Asteraceae) as a model system. It is known that cis-regulatory sequences for mesophyll-specific expression of the ppcA1 gene of F. trinervia (C4) are located within a distal promoter region (DR).


RESULTS
In this study we focus on the proximal region (PR) of the ppcA1 promoter of F. trinervia and present an analysis of its function in establishing a C4-specific expression pattern. We demonstrate that the PR harbours cis-regulatory determinants which account for high levels of PEPC expression in the leaf. Our results further suggest that an intron in the 5' untranslated leader region of the PR is not essential for the control of ppcA1 gene expression.


CONCLUSIONS
The allocation of cis-regulatory elements for enhanced expression levels to the proximal region of the ppcA1 promoter provides further insight into the regulation of PEPC expression in C4 leaves.
Engelmann
Sascha
S
Institut für Entwicklungs- und Molekularbiologie der Pflanzen, Heinrich-Heine-Universität, Universitätsstr, 1, 40225 Düsseldorf, Germany. engelmas@uni-duesseldorf.de
Zogel
Corinna
C
Koczor
Maria
M
Schlue
Ute
U
Streubel
Monika
M
Westhoff
Peter
P
D020121:5' Untranslated Regions; D001483:Base Sequence; D019143:Evolution, Molecular; D037142:Flaveria / Q000201:enzymology / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D007438:Introns; D008969:Molecular Sequence Data; D010730:Phosphoenolpyruvate Carboxylase / Q000235:genetics* / Q000378:metabolism; D018515:Plant Leaves / Q000201:enzymology; D030821:Plants, Genetically Modified / Q000201:enzymology; D011401:Promoter Regions, Genetic; D017384:Sequence Deletion; D012689:Sequence Homology, Nucleic Acid
D020121:5' Untranslated Regions; D010730:Phosphoenolpyruvate Carboxylase