Abstract
BackgroundBemisia tabaci MEAM1 (Middle East-Asia Minor 1) feeding alters antioxidative enzyme activity in some plant species. Infestation of B. tabaci nymphs decreases Myzus persicae performance on systemic, but not local leaves of tobacco plants. However, it is unclear if B. tabaci nymphs induced antioxidant activities contributing to the aphid resistance.Methodology/Principal FindingsWe investigated the relationship between antioxidants induced by nymphs of B. tabaci feeding on tobacco and aphid resistance. The activities of catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and the concentration of hydrogen peroxide (H2O2) were assayed in tobacco leaves at different feeding times following infestation of B. tabaci nymphs. The infestation altered the activities of CAT and POD, but had no significant effect on SOD activity. The highest CAT activity was observed at 15 d after infestation. This was 98.2% greater than control systemic leaves, but 32.6% lower than the control in local leaves. Higher POD activity was recorded in local vs. systemic leaves after 15 d of infestation. POD activity was 71.0% and 112.9% higher in local and systemic leaves, respectively, than in the controls. The changes of CAT, but not POD or SOD activity were correlated to levels of aphid resistance. H2O2 levels were higher in local than in systemic leaves in contrast to CAT activity. Tobacco curly shoot virus mediated virus-induced gene silencing was employed to determine if CAT activation was involved in the aphid resistance induced by B. tabaci nymphs. B. tabaci induced CAT activity decreased when the Cat1 expression was silenced. The performance assay indicated that Cat1 silencing made B. tabaci infested plants a more suitable host for aphids than infested control plants. The aphid survival rate was reduced by 40.4% in infested control plants, but reduced by only 26.1% in Cat1-silenced plants compared to uninfested controls. Also, qPCR results showed that silencing of Cat1 led to the suppression of the B. tabaci mediated PR-2a expression.Conclusions/SignificanceAphid resistance in plants infested with B. tabaci nymphs is associated with enhanced antioxidant activities in which CAT may play a dominant role. This resistance probably acted via interactions with SA-mediated defense responses.
Highlights
Defense responses are often induced in terrestrial plants following attack by pathogens or insects
The activities of CAT in local and systemic leaves of B. tabaci infested plants were not significantly different from controls until 15 d, when CAT activity was significantly higher than controls by 98.2% systemically (F = 21.233; df = 1,31; P = 0.000), while 32.6% lower than in controls locally (F = 3.072; df = 1,31; P = 0.042) (Fig 1A & 1B)
Induced plant resistance could be correlated with the redox status of the host tissue, which is achieved by the generation of reactive oxygen species (ROS) and their subsequent elimination [35, 62]
Summary
Defense responses are often induced in terrestrial plants following attack by pathogens or insects. These responses may be localized in the damaged tissue or systemic in undamaged tissue. To prevent oxidation burst due to ROS production, plants have evolved complex protective mechanisms for scavenging ROS These include the enzymatic scavenging systems, such as catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) [10]. Infestation of B. tabaci nymphs decreases Myzus persicae performance on systemic, but not local leaves of tobacco plants. It is unclear if B. tabaci nymphs induced antioxidant activities contributing to the aphid resistance
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