TEMPORARY PARTIAL BREAKDOWN OF mlo RESISTANCE
SJ BAKER1, AC NEWTON2 and SJ GURR1
1Department of Plant Sciences, South Parks Road, University of Oxford, OX1 3RB, UK; 2Scottish Crop Research Institute, lnvergowrie, Dundee, DD2 5DA, Scotland, UK
Background and objectives
Results and conclusions
A comprehensive microscopic examination has determined the cellular characteristics of breakdown. The optimal time-point for resistance breakdown, upon relief of water stress, was found to be 7 h post-inoculation. The degree of breakdown was shown to vary with cell type; notably colony formation on short cells was shown to increase from less than 1 in 100 to more than 1 in 10. Principal components analysis (PCA) has been used to demonstrate that host reactions in resistant and susceptible cultivars can be distinguished at 7 h post-inoculation.
Peroxidases play an important role in both papilla-based resistance and plant responses to water stress where they are involved in protein cross-linking and protection from oxidative damage, respectively. mlo-Resistant plants show more extensive protein cross-linking around reaction sites, in terms of halo size, than mlo-susceptible plants; this phenomenon is reduced under water stress. Furthermore, at the critical time-point, 7 h post-inoculation, protein cross-linking reaction sites were found to be more frequent in non-stressed plants than in water-stressed plants, suggesting that the speed of response is reduced in water-stressed plants. An investigation to assess the effect of relief of water stress on peroxidase transcript levels during pathogenesis and wounding is being carried out.
SJB holds a BBSRC CASE Studentship with SCRI.