Abstract
Elevated ozone (O3) modulates phytohormone signals, which subsequently alters the interaction between plants and herbivorous insects. It has been reported that elevated O3 activates the plant abscisic acid (ABA) signaling pathway, but its cascading effect on the performance of herbivorous insects remains unclear. Here, we used the ABA-deficient tomato mutant notabilis (not) and its wild type, Ailsa Craig (AC), to determine the role of ABA signaling in mediating the effects of elevated O3 on Bemisia tabaci in field open-top chambers (OTCs). Our results showed that the population abundance and the total phloem-feeding duration of B. tabaci were decreased by O3 exposure in AC plants compared with not plants. Moreover, elevated O3 and B. tabaci infestation activated the ABA signaling pathway and enhanced callose deposition in AC plants but had little effect on those in not plants. The exogenous application of a callose synthesis inhibitor (2-DDG) neutralized O3-induced resistance to B. tabaci, and the application of ABA enhanced callose deposition and exacerbated the negative effects of elevated O3 on B. tabaci. However, the application of 2-DDG counteracted the negative effects of O3 exposure on B. tabaci in ABA-treated AC plants. Collectively, this study revealed that callose deposition, which relied on the ABA signaling pathway, was an effective O3-induced priming defense of tomato plants against B. tabaci infestation.
Highlights
The global tropospheric ozone (O3) concentration has increased from less than 10 ppb in the preindustrial era to 35-50 ppb in the present day in the Northern Hemisphere (Ainsworth et al, 2012) and is predicted to increase at a rate of approximately 0.5-2% per year in some regions, such as East Asia (Ohara et al, 2007; IPCC, 2013; Cooper et al, 2014)
For the feeding behavior of B. tabaci, elevated O3 increased the total duration of salivating into sieve elements (E1 phase) by 47%, decreased the total duration of phloem ingestion by 26%, and prolonged the total time to the first E2 by 50% when reared on the Ailsa Craig (AC) plants, but the total duration of E1, the total duration of E2, and the total time to the first E2 were not affected by elevated O3 when B. tabaci was reared on the not plants
We reported that elevated O3 induced callose deposition in tomato plants and enhanced plant resistance to B. tabaci in terms of reducing feeding efficiency and population abundance
Summary
The global tropospheric ozone (O3) concentration has increased from less than 10 ppb in the preindustrial era to 35-50 ppb in the present day in the Northern Hemisphere (Ainsworth et al, 2012) and is predicted to increase at a rate of approximately 0.5-2% per year in some regions, such as East Asia (Ohara et al, 2007; IPCC, 2013; Cooper et al, 2014). We hypothesized that elevated O3 increased ABA signal-regulated callose deposition, which could be detrimental to the population abundance and feeding efficiency of B. tabaci. To experimentally test this hypothesis, we used notabilis (not, an ABA-deficient mutant of Lycopersicon esculentum) and its wild type, Ailsa Craig (AC, background of not), to determine the effects of elevated O3 on the ABA signaling pathway of the tomato plant and its cascading effect on the performance of B. tabaci. Our specific objectives were to determine (1) whether elevated O3 activates the ABA signaling pathway; (2) whether O3-induced upregulation of the ABA signaling pathway causes further accumulation of callose; and (3) whether ABA signaling is involved in regulating the effects of elevated O3 on the feeding behavior and population abundance of B. tabaci
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