Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 4/15/2008
Publication Date: 7/8/2008
Citation: Winters, A.L., Gill, S., Heywood, S., Parveen, I., Sullivan, M.L., Webb, K.J. 2008. Role of red clover PPO in pathogen resistance [abstract]. XXIVth International Conference on Polyphenols, July 8-11, 2008, Salamanca, Spain. Abstract No. T3.28.
Technical Abstract: Higher plant polyphenol oxidases (PPO) are copper-containing enzymes which catalyse both hydroxylation of monophenols to o-diphenols and oxidation of o- diphenols to o-quinones. While PPO is widespread in the plant kingdom, its role in plants has not been unequivocally determined; however, evidence suggests a role in plant defence. We have isolated a low PPO mutant red clover line expressing greatly reduced levels of PPO compared with the wild type. Low PPO mutants (clonal lines and plants grown from seed) have shown increased susceptibility to thrips attack compared with wild-type plants. Wild-type and mutant plants grown in controlled environmental conditions became stressed following cutting and became infected with thrips. Both populations showed typical markings on leaves associated with thrips infection; however, these were much more extensive on low PPO mutant plants. In addition, thrips infection severely affected growth of mutant plants, while no obvious effect on growth of wild-type plants was observed. We will present data on PPO transcripts and PPO enzyme activity and substrate in wild-type and mutant plants infected with thrips. Low PPO mutant and transgenic knock-out red clover plants also show susceptibility to attack by sciarid fly. Counts of adult sciarid flies over apparently healthy wild-type and mutant plants, including clonal lines and plants grown from seed, show approximately twice as many flies associated with mutant compared with wild-type plants. When grown in controlled environmental conditions and subjected to the abiotic stress of defoliation and shading, both PPO transgenic knock-out and wild-type plants were severely damaged by sciarid larvae. We will present data on the analysis of nitrogen released into leachate collected from under these contrasting phenotypes.