Planta

, Volume 203, Issue 4, pp 454–459 | Cite as

Molecular cloning of a cDNA encoding a (1→4)-β-mannan endohydrolase from the seeds of germinated tomato (Lycopersicon esculentum)

  • J. Derek Bewley
  • Rachel A. Burton
  • Yukio Morohashi
  • Geoffrey B. Fincher
Article

Abstract.

Mannose-containing polysaccharides are widely distributed in cell walls of higher plants. During endosperm mobilization in germinated tomato seeds (1→4)-β-mannan endohydrolases (EC 3.2.1.78) participate in the enzymic depolymerization of these cell wall polysaccharides. A cDNA encoding a (1→4)-β-mannanase from the endosperm of germinated tomato (Lycopersicon esculentum Mill.) seeds has been isolated and characterized. The amino acid sequence deduced from the 5′-region of the cDNA exactly matches the sequence of the 65 NH2-terminal amino acids determined directly from the purified enzyme. The mature enzyme consists of 346 amino acid residues, it has a calculated Mr of 38 950 and an isoelectric point of 5.3. Overall, the enzyme exhibits only 28–30% sequence identity with fungal (1→4)-β-mannanases, but more highly conserved regions, which may represent catalytic and substrate-binding domains, can be identified. Based on classification of the tomato (1→4)-β-mannanase as a member of the family 5 group of glycosyl hydrolases, Glu-148 and Glu-265 would be expected to be the catalytic acid and the catalytic nucleophile, respectively. Southern hybridization analyses indicate that the enzyme is derived from a family of about four genes. Expression of the genes, as determined by the presence of mRNA transcripts in Northern hybridization analyses, occurs in the endosperm of germinated seeds; no transcripts are detected in hypocotyls, cotyledons, roots or leaves.

Key words: Cell wall Endosperm mobilization Gene expression patterns Lycopersicon (1→4)-β-Mannan endohydrolase (primary structure) Polysaccharide 

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Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • J. Derek Bewley
    • 1
  • Rachel A. Burton
    • 2
  • Yukio Morohashi
    • 3
  • Geoffrey B. Fincher
    • 2
  1. 1.Department of Botany, University of Guelph, Guelph, Ontario N1G 2W1, CanadaCA
  2. 2.Department of Plant Science, University of Adelaide, Waite Campus, Glen Osmond, S.A. 5064, AustraliaAU
  3. 3.Department of Regulation Biology, Faculty of Science, Saitama University, Urawa, Saitama 338, JapanJP

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