A molecular biological study of the biosynthesis of flavour precursors in garlic, Allium sativum L.

1
A molecular biological study of the biosynthesis
of flavour precursors in garlic, Allium sativum L.
Angela Tregova Hamish A Collin, Meriel G Jones,
Brian Tomsett, Jill Hughes
2
Objectives

• Identify genes involved in CSO biosynthesis
• Novel enzymes
• Known enzymes with novel functions

3
What have we found?

• Arabidopsis transport protein (ER Golgi)
• Sensory transduction histidine kinase
• ATPase subunit 9 (mitochondrial)
• Mouse RalGDD-like protein 3
• Methanococcus hypothetical protein
• Viral envelope/polymerase protein
• Arabidopsis hypothetical protein (x2)
• 4 bands nothing in database

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The Way Forward

• Differential display works - but no genes
  involved in S metabolism found yet
• Consider alternative strategies
• From S biochemistry, cysteine synthase is
  candidate

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Sulphur metabolism

• SO4 SO3 S Serine
• Methionine Cysteine O-acetyl serine
• Alk(en)yl CSOs

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Formation of ?-substituted alanines and
S-substituted L-cysteines

• Serine
•  
• SAT/CS
• Complex
•  
• OAS
•   H2S CH2CH-CH2-SH MeSH
  3,4-Dihydroxy- Pyrazol
• Free CS pyridine
•  
•  
• L-Cysteine S-Allyl-L-cysteine
  S-Methyl- Mimosine ?-PA
• L-cysteine
•  
•  Free CAS HCN CH2CH-CH2-SH
•  
• 3-Cyano-L-Ala S-Allyl-L-cysteine

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Aims

• Isolate multiple SATases and CSases from garlic
• Investigate the the ability of each enzyme to
  produce S-allyl-L-cysteine

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Progress up-to-date

• Produced combined cDNA library for all the
  tissues (root, clove, leaf)
• PCR amplification of garlic specific cDNA
  fragments
• Cytoplasmic / mitochondrial CSase
• Chloroplastic CSase
• SATase