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Abstract
Elevated ozone (O3) can alter the phenotypes of host plants particularly in induction of leaf senescence, but few reports examine the involvement of phytohormone in O3-induced changes in host phenotypes that influence the foraging quality for insects. Here, we used an ethylene (ET) receptor mutant Nr and its wild-type to determine the function of the ET signaling pathway in O3-induced leaf senescence, and bottom-up effects on the performance of Bemisia tabaci in field open-top chambers (OTCs). Our results showed that elevated O3 reduced photosynthetic efficiency and chlorophyll content and induced leaf senescence of plant regardless of plant genotype. Leaf senescence in Nr plants was alleviated relative to wild-type under elevated O3. Further analyses of foliar quality showed that elevated O3 had little effect on phytohormone-mediated defenses, but significantly increased the concentration of amino acids in two plant genotypes. Furthermore, Nr plants had lower amino acid content relative to wild-type under elevated O3. These results provided an explanation of O3-induced increase in abundance of B. tabaci. We concluded that O3-induced senescence of plant was ET signal-dependent, and positive effects of O3-induced leaf senescence on the performance of B. tabaci largely resulted from changes of nutritional quality of host plants.
Highlights
Global tropospheric ozone (O3) concentration has increased from pre-industrial less than 10 to current 35–50 ppb in the Northern hemisphere (Ainsworth et al, 2012), and is predicted to be still increasing 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)
Elevated O3 significantly increased the ET production by 37% in Ailsa Craig (AC) plants spraying with H2O (AC/H2O plants), by 24% in AC plant spraying with ACC (AC/ACC plants), and by 38% in Never ripe (Nr) plants spraying with H2O (Nr/H2O plants)
The expression of foliar ACO and ACS genes were consistent with the level of ET emission, which were upregulated under elevated O3 in AC/H2O plants, AC/ACC plants, and Nr/H2O plants (Figures 1B,C)
Summary
Global tropospheric ozone (O3) concentration has increased from pre-industrial less than 10 to current 35–50 ppb in the Northern hemisphere (Ainsworth et al, 2012), and is predicted to be still increasing 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). Tropospheric O3 is an important atmospheric pollution type and a greenhouse gas, which can cause changes in plant metabolism, such as changes in photosynthetic rate, nutritional content, and secondary compounds (Ashmore, 2005; Gupta et al, 2005). Ethylene (ET) signaling pathway is widely accepted as a positive mediator of developmental leaf senescence, in which leaf senescence is delayed or alleviated for ET-insensitive mutants, and accelerated for plants exogenous application of ET (Lim et al, 2007; Koyama, 2014; Qiu et al, 2015). Recent research demonstrated that ET signaling pathway serves as a positive mediator in abiotic stress-induced leaf senescence, such as drought or heat stress (Young et al, 2004). ET production and its signaling pathway are upregulated under elevated O3 (Moeder et al, 2002; Ludwików et al, 2009, 2014), it is unclear the role of ET signaling pathway in O3-induced leaf senescence
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