The modular nodulins Nvf-28/32 of broad bean (Vicia faba L.): alternative exon combinations account for different modular structures

• Published in: Molecular & general genetics Vol. 252; no. 6; p. 648
• Main Authors: Kuester H, Fruehling M, Puehler A, Perlick A.M
• Format: Journal Article
• Language: English
• Published: Germany 28.10.1996
• Subjects: Alternative Splicing; Amino Acid Sequence; Base Sequence; Exons; Fabaceae - genetics; gene; genes; Genome, Plant; In Situ Hybridization; Membrane Proteins; Molecular Sequence Data; nucleotide sequence; Plant Proteins - genetics; Plants, Medicinal; secuencia nucleotidica; sequence nucleotidique; Transcription, Genetic; vicia faba
• ISSN: 0026-8925; 1432-1874
• DOI: 10.1007/BF02173970

The broad bean late nodulins, Nvf-28/32, are composed of two types of repetitively occurring sequence modules flanked by unique N- and C-terminal modules. Six isoforms of these nodulins were characterized by a specific modular structure resulting from a different individual order of repetitive sequence modules. A detailed analysis of genomic PCR fragments revealed that the repetitive modules and the N-terminal unique module exactly corresponded to exons, whereas the C-terminal module was specified by two exons. Since those exons encoding the repetitive modules missing in specific Nvf-28/32 isoforms were consistently present within genomic sequences, a post-transcriptional generation of VfNOD28/32 transcripts specifying six Nvf-28/32 nodulins was concluded. Using tissue-print hybridizations, these transcripts were localized in the interzone II-III and the nitrogen-fixing zone III of root nodules. From this and from cDNA-cDNA hybridizations demonstrating a comparable timing of expression of VfNOD28/32 and of leghemoglobin transcripts in root nodules, a function of the modular nodulins Nvf-28/32 in late developmental stages of broad bean nodules was inferred.