Cell wall alterations and localized accumulation of feruloyl-3′-methoxytyramine in onion epidermis at sites of attempted penetration by Botrytis allii are associated with actin polarisation, peroxidase activity and suppression of flavonoid biosynthesis

Authors

  • Sarah R. McLusky,

    1. Department of Biological Sciences, Wye College, University of London, Ashford, Kent TN25 5AH, UK, and
    2. I.A.C.R., Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, UK
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  • Mark H. Bennett,

    1. Department of Biological Sciences, Wye College, University of London, Ashford, Kent TN25 5AH, UK, and
    2. I.A.C.R., Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, UK
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  • Michael H. Beale,

    1. I.A.C.R., Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, UK
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  • Mervyn J. Lewis,

    1. I.A.C.R., Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, UK
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  • Paul Gaskin,

    1. I.A.C.R., Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, UK
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  • John W. Mansfield

    1. Department of Biological Sciences, Wye College, University of London, Ashford, Kent TN25 5AH, UK, and
    2. I.A.C.R., Long Ashton Research Station, Department of Agricultural Sciences, University of Bristol, Long Ashton, Bristol BS41 9AF, UK
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  • The Plant Journal (1999) 17(5), 523–534

*For correspondence (fax +12 338 13140; e-mail j.mansfield@wye.ac.uk ).
†Joint first authors.

Summary

Granular deposits of reaction material (RM) were formed in onion epidermal cells at sites of attempted penetration byBotrytis allii. Both RM and the adjacent cell wall fluoresced blue under UV excitation. The blue autofluorescence was caused primarily by the accumulation of feruloyl-3′-methoxytyramine (FMT) and feruloyltyramine (FT) within challenged tissues. Additional phenolics increasing at infection sites were identified as coumaroyl glucose, coumaroyltyramine (CT) and 2-hydroxy-2-(4-hydroxyphenyl) ethylferulate. The major autofluorescent components of RM, the hydroxycinnamic acid amides FMT and FT, were bound by ether linkage onto the cell wall as well as being present in methanol soluble granules. Formation of RM was associated with early increases in peroxidase activity detected by histochemistry at reaction sites and striking polarisation of actin microfilaments. Quantitative analysis of quercetin and cyanidin glucosides revealed that the localized synthesis and deposition of feruloyltyramine derivatives was associated with suppression of flavonoid and anthocyanin accumulation in a zone of cells around those accumulating RM. No antifungal activity was detected in FMT, FT or CT, nevertheless it is proposed that the phenolics have a key role in resistance by preventing fungal degradation of the cell wall.

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