Changes in the location of polyphenol oxidase in potato (Solanum tuberosumL) tuber during cell death in response to impact injury: comparison with wound tissue

In order to elucidate the nature of the response of potato to impact injury at the biochemical level, changes in the location of the enzyme responsibl e for the discoloration, polyphenol oxidase, were determined using immunogo ld location with an antibody specific for potato tuber polyphenol oxidase. Tissue printing revealed that the enzyme was distributed throughout the tub er. Following impact injury, both tissue printing and quantitative electron microscopy indicated that there was no increase in the level of the enzyme although there was subcellular redistribution of polyphenol oxidase. This redistribution was first apparent at 12 h after impact, as determined by th e use of confocal immunolocation, and coincided with loss of membrane integ rity. These changes were examined in parallel with a number of stress-relat ed parameters in both impact and wound responses. Wounding was accompanied by active gene expression and protein synthesis, leading to metabolic activ ity and tissue repair. In contrast, the bruising response was characterised by a limited active response and vital-staining methods indicated that aft er 16 h the tissue undergoes cell death.