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Analyses of phosphoenolpyruvate carboxylase gene structure and expression in alfalfa nodules
Author(s) -
Pathirana M. Sudam,
Samac Deborah A.,
Roeven Robert,
Yoshioka Hirofumi,
Vance Carroll P.,
Gantt J. Stephen
Publication year - 1997
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1046/j.1365-313x.1997.12020293.x
Subject(s) - phosphoenolpyruvate carboxylase , biology , intron , gene , exon , meristem , transcription (linguistics) , gene expression , microbiology and biotechnology , untranslated region , transgene , rna , genetics , linguistics , philosophy
Phosphoenolpyruvate carboxylase (PEPC) plays a crucial role in the assimilation of CO 2 during symbiotic N 2 fixation in legume root nodules. In this study, an alfalfa PEPC gene ( PEPC‐7 ), whose transcripts are found at elevated levels in nodules relative to either leaves or roots, has been isolated and characterized. The intron/exon structure of this gene is identical to that of most other plant PEPC genes except for the presence of an additional intron in the 5′ untranslated region. In situ RNA hybridization studies showed that PEPC transcripts were present in the nodule meristem, the infection zone, the nitrogen‐fixing zone, and the parenchyma. PEPC transcripts were also found in vascular tissue of roots and nodules and in the pulvinus of petioles. In transgenic alfalfa, a chimeric reporter gene was expressed in these same regions except that little expression was found in the nodule meristem. Analyses of promoter deletions suggest that the region between −634 and −536 is of particular importance in directing transcriptional activity to the infected zone of nodules. Within this region is a mirror repeat sequence that is potentially capable of forming an H‐DNA structure. These results indicate that PEPC‐7 has a central role in nitrogenfixing nodules and that regulation of transcription is an important determinant of its activity.