Plant Physiol, March 2003, Vol. 131, pp. 1440-1449
Biphasic Superoxide Generation in Potato Tubers. A
Self-Amplifying Response to Stress1
S.M.
Johnson,
S.J.
Doherty,2 and
R.R.D.
Croy*
Crop Protection Group, School of Biological and Biomedical
Sciences, University of Durham, South Road, Durham DH1 3LE, United
Kingdom
Potato (Solanum tuberosum) cultivars differ
quantitatively in their responses to mechanical stress including the
ability to synthesize melanin pigments in tuber tissues. Investigations
into the cellular events induced by mechanical stress on tuber tissues have shown that an early cellular response is a significant and rapid
synthesis of superoxide radicals. This burst of radical production
distinctively displays a reproducible biphasic pattern over time with
peaks of generation at 2 and 5 h. A concomitant consequence of the
generation of these free radicals is elevated levels of oxidatively
modified tuber proteins. Both radical generation and protein
modification vary between cultivars but both are directly proportional
to the amount of melanin pigments produced. Cell-free extracts of
mechanically stressed tissues, pectic fragments, and scission products
generated from cell walls are able to induce superoxide generation in
non-stressed tissues, indicating the participation of a biologically
active factor that induces a further a phase of radical synthesis.
1
This work was supported by the British Potato
Council, Department for Environment, Farming and Rural Affairs and by
the University of Durham. S.J.D. was the recipient of a Special
Studentship from the Biological and Biotechnology Research Council.
2
Present address: Avecia Life Science Molecules, Belasis
Avenue, Billingham, Teesside TS25 1TN, UK.
*
Corresponding author; e-mail R.R.D.Croy{at}durham.ac.uk; fax
44-191-374-2417.
© 2003 American Society of Plant Biologists
