Biosynthetic threonine deaminase gene of tomato: isolation, structure, and upregulation in floral organs

• Published in: Proceedings of the National Academy of Sciences - PNAS 1991-04, Vol.88 (7), p.2678-2682
• Main Authors: Samach, A., Hareven, D., Gutfinger, T., Ken-Dror, S., Lifschitz, E.
• Format: Article
• Language: English
• Subjects: actividad enzimatica; activite enzymatique; Amino Acid Sequence; Base Sequence; Biological and medical sciences; Biosynthesis; Calyx; code genetique; codigo genetico; Complementary DNA; Enzymes; enzymic activity; expresion genica; expression des genes; Flowers; Fundamental and applied biological sciences. Psychology; gene; gene expression; Gene Library; genes; Genes, Plant; Genes, Synthetic; Genes. Genome; genetic code; Genomics; Introns; liasas; lyase; lyases; Lycopersicon esculentum; Mesophyll cells; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; nucleotide; nucleotides; nucleotidos; Plant Physiological Phenomena; Plants; Plants - enzymology; Plants - genetics; Restriction Mapping; Sequence Homology, Nucleic Acid; TATA Box; Threonine Dehydratase - genetics; Transcription, Genetic; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.88.7.2678

The gene encoding the plant biosynthetic threonine deaminase (Td; EC 4.2.1.16) has been cloned as a result of its unusual upregulation in tomato flowers. The Td gene of tomato encodes a polypeptide of 595 residues, the first 80 of which comprise a putative two-domain transit peptide cleaved at position 51. Comparison of the amino acid sequence with the corresponding enzymes from yeast and bacteria reveals a near identity of the important catalytic regions and >40% overall similarity. The Td gene is unique in the tomato genome and its coding region is interrupted by eight introns. Its expression is >50-fold higher in sepals and >500-fold higher in the rest of the flower than in leaves or roots. Its overexpression, however, is strictly confined to the parenchymal cells of the floral organs. In young tomato leaves, the chloroplast-bound enzyme is found almost exclusively in the subepidermal spongy mesophyll cells.