O3-Induced Leaf Senescence in Tomato Plants Is Ethylene Signaling-Dependent and Enhances the Population Abundance of Bemisia tabaci

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.

Antioxidants and Phytohormones Act in Coordination to Regulate Sage Response to Long Term Ozone Exposure

“…We speculated that a synergistic interaction among SA, ET and ABA may modulate the defense responses and, at the same time, the magnitude of chlorosis in response to O 3 exposure. Similar results were previously reported by Guo et al [ 35 , 36 ] and interpreted as a marker of O 3 -induced leaf senescence [ 35 , 36 ]; this is an aspect that warrants more investigation in order to deeply understand the dual roles of these molecules, as well as the study of these stress-response pathways at a gene expression level. Furthermore, given that increasing O 3 concentrations and other environmental stresses (e.g., elevated CO 2 level, drought, and UV) usually occur together, more research would be interesting to further investigate the interactive impacts of multiple environmental stresses on the orchestrated regulations highlighted by the present study.…”

“…It should be noted that the synthesis and/or the regeneration of these low molecular weight antioxidant compounds to their reduced powerful antioxidant forms (due to LA after reduction to DHLA as observed at 7 and 14 days FBE) were not able to protect membranes from lipid peroxidation, as demonstrated by the accumulation of MDA (one of the major indicators of cell membrane damage; [ 33 ]) from 14 days FBE and even more at the last times of analysis. However, these processes of lipid oxidation did not include the synthesis of the membrane breakdown products formed by LOX, as confirmed by the highly variable response of this enzyme to O 3 exposure (which decreased at 7 and 14 days FBE, and increased only at 29 days FBE, when most severe symptoms and physiological impairments were first reported) and the unchanged values of JA (thus confirming that this compound was not involved in the regulation of PCD strategies; [ 34 , 35 , 36 ]). In addition, Marchica et al [ 22 ] documented that the composition of volatile products of LOX pathway (such as C 6 aldehydes and alcohols and their derivatives) was slightly affected by O 3 exposure (under the same experimental conditions), suggesting that after a progression of oxidative pressure until 29 days FBE, sage then settled into a stable stress state until the end of exposure (in terms of free fatty acids released by phospholipases from membranes in response to O 3 ), confirming a capability of this species to tolerate long-term O 3 exposure for several weeks.…”

O3-Induced Priming Defense Associated With the Abscisic Acid Signaling Pathway Enhances Plant Resistance to Bemisia tabaci

“…After 18 days of O 3 fumigation, leaves from the third or fourth branch (counting from the top) of each plant (8 AC plants and 8 not plants) per OTC were randomly selected to measure ROS content according to a modified method described previously (Guo et al, 2018) (Figure S.1A).…”

“…After 39 days of O 3 fumigation, leaves from the third or fourth branch (counting from the top) of tomato plants with and without B. tabaci infestation were collected for ABA measurements. Approximately 300 mg of fresh leaves were used to analyze the ABA content according to a modified method that was described previously (Guo et al, 2018). Plant tissue was homogenized in liquid nitrogen and sealed in 10 ml tubes.…”

“…The RNeasy Mini Kit (Qiagen, Dusseldorf, Germany) was used to isolate total RNA from the leaves (0.05 g from samples stored at -70°C), and 1 mg of RNA was used to generate cDNA. We used real-time quantitative PCR (qPCR) to determine the mRNA levels according to a modified method that was described previously (Guo et al, 2018). Specific primers for each gene were designed from the expressed sequence tag sequences using Primer 5 software (Table S.7).…”