Changes in the activities of antioxidant enzymes in response to virus infection and hormone treatment
Authors: Clarke, SF; Guy, PL; Burritt, DJ; Jameson, PE
Activities of enzymes involved in the detoxification of reactive oxygen species (catalase, glutathione reductase, peroxidase and superoxide dismutase (SOD)) were examined in the leaves of Phaseolus vulgaris L. var. Top Crop treated with plant hormones and infected with a non-lesion-forming isolate of white clover mosaic potexvirus (WClMV). The activities of catalase, glutathione reductase and SOD rapidly declined after infection while peroxidase activity was enhanced. These changes occurred before the rapid increase (5 days) in WClMV replication. A mild chlorosis appeared 7-10 days after inoculation but necrosis was never observed on inoculated leaves. Plants treated with dihydrozeatin, salicylic acid and jasmonic acid prior to WCIMV inoculation showed elevated catalase, glutathione reductase, and peroxidase activity, while SOD activities remained the same as in water-treated controls. These treatments all inhibited virus replication with enzyme activities remaining near control levels. We propose that a decline in free radical scavenging capacity may be required before a rapid increase in virus replication can take place. Treatments increasing the ability of the plant to scavenge reactive oxygen species may hinder virus replication. A possible role for reactive oxygen species as a requirement for virus replication is discussed.
Influence of white clover mosaic potexvirus infection on the endogenous levels of jasmonic acid and related compounds in Phaseolus vulgaris L. seedlings
JOURNAL OF PLANT PHYSIOLOGY
Authors: Clarke, SE; Guy, PL; Jameson, PE; Schmierer, D; Burritt, DJ
Primary leaves of 16-day-old Phaseolus vulgaris L, seedlings were inoculated with either white clover mosaic potexvirus (WClMV) or water. The concentrations of jasmonic acid (JA), dihydrojasmonic acid (DHJA) and cucurbic acid (CA), and virus titre were measured over a ten day period following inoculation. A transient increase in the concentration of JA occurred immediately following inoculation with water or WClMV, which we attribute to wounding. A second increase in JA occurred only in virus-infected leaves. Concentrations of cucurbic and dihydrojasmonic acids were not affected by wounding, but virus-infection resulted in a decline in the concentration of CA and an increase in DHJA. Reasons for the changes in jasmonate concentrations after virus infection are discussed.