A carbonic anhydrase gene is induced in the nodule primordium and its cell‐specific expression is controlled by the presence of Rhizobium during development

• Published in: The Plant journal : for cell and molecular biology Vol. 11; no. 3; pp. 407 - 420
• Main Authors: Peña, Teodoro Coba, Frugier, Florian, McKhann, Heather I., Bauer, Petra, Brown, Spencer, Kondorosi, Adam, Crespi, Martin
• Format: Journal Article
• Language: English
• Published: Blackwell Science Ltd, Osney Mead, Oxford OX2 0EL, UK Blackwell Science Ltd 01.03.1997; Blackwell Science
• Subjects: Agronomy. Soil science and plant productions; Amino Acid Sequence; Biological and medical sciences; Carbonic Anhydrases - biosynthesis; Carbonic Anhydrases - chemistry; Economic plant physiology; Enzyme Induction; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Developmental; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Medicago sativa; Medicago sativa - enzymology; Medicago sativa - growth & development; Medicago sativa - microbiology; Molecular Sequence Data; Parasitism and symbiosis; Plant physiology and development; Plant Roots; Plants - enzymology; Rhizobium meliloti; Sequence Homology, Amino Acid; Sinorhizobium meliloti - physiology; Symbiosis; Symbiosis (nodules, symbiotic nitrogen fixation, mycorrhiza...); Transcription, Genetic; Symbiosis; Symbionte; Rhizobium meliloti; Root; Enzyme; Deficiency; Medicago sativa; Nodulation; Lyases; Nitrogen; Gene expression; Leguminosae; Enzymatic activity; Dicotyledones; Angiospermae; Bacteria; Spermatophyta; Carbonate dehydratase; Fodder crop; Rhizobiaceae; Carbon-oxygen lyases; Aminoacid sequence; Hydro-lyases
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1997.11030407.x

Summary Under nitrogen starvation, Rhizobium meliloti is able to induce nitrogen‐fixing nodules on alfalfa roots. Certain alfalfa cultivars spontaneously develop pseudonodules in the absence of bacteria. A transcript, Msca1, expressed in spontaneous and R. meliloti‐induced nodules, that codes for a carbonic anhydrase (CA), an enzyme catalyzing the hydration of CO2 has been identified. This is the first CA gene cloned from a non‐photosynthetic tissue in plants. Msca1 was activated initially in all cells of the bacterium‐induced nodule primordium and was also induced by cytokinin treatment of alfalfa roots. The presence of CA enzymatic activity in different nodule types was demonstrated. Thus, Msca1 is a new early nodulin gene with a function possibly related to the increased amyloplast deposition of the dividing cortical cells. Msca1 transcripts were subsequently found mainly in a peripheral envelope of cells in developing and mature nodules. This novel pattern of gene expression is controlled by the presence of the bacterium inside the nodule. Sucrose synthase and phosphoenol pyruvate carboxylase (PEPC), other genes of the carbon fixation metabolism, were expressed in the same peripheral cells and even more strongly in the nitrogen‐fixing region. Analysis of expression patterns of these genes indicated that early CA function may not be related to carbon fixation through PEPC. CA might be acting in pH regulation and/or CO2/HCO3− transport during nodule initiation. Thus, carbonic anhydrase may play different roles at several stages of nodule development and function.