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Mason CJ, Peiffer M, Hoover K, Felton G. Tomato Chemical Defenses Intensify Corn Earworm (Helicoverpa zea) Mortality from Opportunistic Bacterial Pathogens. J Chem Ecol 2023; 49:313-324. [PMID: 36964896 DOI: 10.1007/s10886-023-01420-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2022] [Revised: 02/21/2023] [Accepted: 03/13/2023] [Indexed: 03/26/2023]
Abstract
Insect herbivores face multiple challenges to their ability to grow and reproduce. Plants can produce a series of defenses that disrupt and damage the herbivore digestive system, which are heightened upon injury by insect feeding. Additionally, insects face threats from virulent microorganisms that can incur their own set of potential costs to hosts. Microorganisms that invade through the digestive system may function in concert with defenses generated by plants, creating combined assailments on host insects. In our study, we evaluated how tomato defenses interact with an enteric bacterial isolate, Serratia marcescens, in the corn earworm (Helicoverpa zea). We performed bioassays using different tomato cultivars that were induced by methyl jasmonate and larvae orally inoculated with a S. marcescens isolate. Untreated corn earworm larval mortality was low on constitutive tomato, while larvae inoculated with S. marcescens exhibited > 50% mortality within 5 days. Induction treatments elevated both control mortality (~ 45%) and in combination with S. marcescens (> 95%). Larvae also died faster when encountering induced defenses and Serratia. Using a tomato mutant, foliar polyphenol oxidase activity likely had stronger impacts on S. marcescens-mediated larval mortality. Induction treatments also elevated the number of bacterial colony-forming units in the hemolymph of larvae inoculated with Serratia. Larval mortality by S. marcescens was low (< 10%) on artificial diets. Our results demonstrate that plant chemical defenses enhance larval mortality from an opportunistic gut microbe. We propose that the combined damage from both the plant and microbial agent overwhelm the herbivore to increase mortality rates and expedite host death.
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Affiliation(s)
- Charles J Mason
- 501 ASI Building Department of Entomology, The Pennsylvania State University, University Park, PA, 16823, USA.
- Tropical Pest Genetics and Molecular Biology Research Unit, Daniel K Inouye U.S. Pacific Basin Agricultural Research Center, Agricultural Research Service, USDA, 64 Nowelo Street, Hilo, HI, 96720, USA.
| | - Michelle Peiffer
- 501 ASI Building Department of Entomology, The Pennsylvania State University, University Park, PA, 16823, USA
| | - Kelli Hoover
- 501 ASI Building Department of Entomology, The Pennsylvania State University, University Park, PA, 16823, USA
| | - Gary Felton
- 501 ASI Building Department of Entomology, The Pennsylvania State University, University Park, PA, 16823, USA
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Constitutive and Induced Defenses in Long-lived Pines Do Not Trade Off but Are Influenced by Climate. J Chem Ecol 2022; 48:746-760. [PMID: 35982356 DOI: 10.1007/s10886-022-01377-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2022] [Revised: 07/18/2022] [Accepted: 07/19/2022] [Indexed: 10/15/2022]
Abstract
Plants resist herbivores and pathogens by using constitutive (baseline) and inducible (change in defense after an attack) defenses. Inducibility has long been predicted to trade off with constitutive defense, reflecting the economic use of resources. However, empirical evidence for such tradeoffs is variable, and we still lack understanding about when and where defense trade-offs occur. We tested for tradeoffs between constitutive and induced defenses in natural populations of three species of long-lived pines (Pinus balfouriana, P. flexilis, P. longaeva) that differ greatly in constitutive defense and resistance to mountain pine beetle (MPB, Dendroctonus ponderosae). We also assessed how climate influenced constitutive and inducible defenses. At seven high-elevation sites in the western U.S., we simulated MPB attack to induce defenses and measured concentrations of terpene-based phloem defenses on days 0, 15, and 30. Constitutive and induced defenses did not trade off among or within species. Simulated MPB attack induced large increases in defense concentrations in all species independent of constitutive levels. MPB and its symbiotic fungi typically kill trees and thus could be selective forces maintaining strong inducibility within and among species. The contrasting constitutive concentrations in these species could be driven by the adaptation for specializing in harsh, high-elevation environments (e.g., P. balfouriana and P. longaeva) or by competition (e.g., P. flexilis), though these hypotheses have not been empirically examined. Climate influenced defenses, with the greatest concentrations of constitutive and induced defenses occurring at the coldest and driest sites. The interactions between climate and defenses have implications for these species under climate change.
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Soderberg DN, Bentz BJ, Runyon JB, Hood SM, Mock KE. Chemical defense strategies, induction timing, growth, and trade‐offs in
Pinus aristata
and
Pinus flexilis. Ecosphere 2022. [DOI: 10.1002/ecs2.4183] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- David N. Soderberg
- Wildland Resources Department Utah State University Logan Utah USA
- Ecology Center Utah State University Logan Utah USA
| | - Barbara J. Bentz
- USDA Forest Service, Rocky Mountain Research Station Logan Utah USA
| | - Justin B. Runyon
- USDA Forest Service, Rocky Mountain Research Station Bozeman Montana USA
| | - Sharon M. Hood
- USDA Forest Service, Rocky Mountain Research Station Missoula Montana USA
| | - Karen E. Mock
- Wildland Resources Department Utah State University Logan Utah USA
- Ecology Center Utah State University Logan Utah USA
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Numbers matter: how irruptive bark beetles initiate transition to self-sustaining behavior during landscape-altering outbreaks. Oecologia 2022; 198:681-698. [DOI: 10.1007/s00442-022-05129-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Accepted: 01/28/2022] [Indexed: 10/19/2022]
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Erbilgin N, Zanganeh L, Klutsch JG, Chen SH, Zhao S, Ishangulyyeva G, Burr SJ, Gaylord M, Hofstetter R, Keefover-Ring K, Raffa KF, Kolb T. Combined drought and bark beetle attacks deplete non-structural carbohydrates and promote death of mature pine trees. PLANT, CELL & ENVIRONMENT 2021; 44:3636-3651. [PMID: 34612515 DOI: 10.1111/pce.14197] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 08/23/2021] [Accepted: 08/24/2021] [Indexed: 06/13/2023]
Abstract
How carbohydrate reserves in conifers respond to drought and bark beetle attacks are poorly understood. We investigated changes in carbohydrate reserves and carbon-dependent diterpene defences in ponderosa pine trees that were experimentally subjected to two levels of drought stress (via root trenching) and two types of biotic challenge treatments (pheromone-induced bark beetle attacks or inoculations with crushed beetles that include beetle-associated fungi) for two consecutive years. Our results showed that trenching did not influence carbohydrates, whereas both biotic challenges reduced amounts of starch and sugars of trees. However, only the combined trenched-bark beetle attacked trees depleted carbohydrates and died during the first year of attacks. While live trees contained higher carbohydrates than dying trees, amounts of constitutive and induced diterpenes produced did not vary between live and beetle-attacked dying trees, respectively. Based on these results we propose that reallocation of carbohydrates to diterpenes during the early stages of beetle attacks is limited in drought-stricken trees, and that the combination of biotic and abiotic stress leads to tree death. The process of tree death is subsequently aggravated by beetle girdling of phloem, occlusion of vascular tissue by bark beetle-vectored fungi, and potential exploitation of host carbohydrates by bark beetle symbionts as nutrients.
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Affiliation(s)
- Nadir Erbilgin
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
| | - Leila Zanganeh
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
- Department of Agriculture and Natural Resources, University of Mohaghegh Ardabili, Ardabil, Iran
| | - Jennifer G Klutsch
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
- Department of Forestry, New Mexico Highlands University, Las Vegas, New Mexico, USA
| | - Shih-Hsuan Chen
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
| | - Shiyang Zhao
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
| | - Guncha Ishangulyyeva
- Department of Renewable Resources, University of Alberta, Edmonton, Alberta, Canada
| | - Stephen J Burr
- Forest Health Protection, USDA Forest Service, Milwaukee, Wisconsin, USA
| | - Monica Gaylord
- Forest Health Protection, USDA Forest Service, Flagstaff, Arizona, USA
| | - Richard Hofstetter
- School of Forestry, Northern Arizona University, Flagstaff, Arizona, USA
| | - Ken Keefover-Ring
- Departments of Botany and Geography, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Kenneth F Raffa
- Department of Entomology, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Thomas Kolb
- School of Forestry, Northern Arizona University, Flagstaff, Arizona, USA
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Why is Tree Drought Mortality so Hard to Predict? Trends Ecol Evol 2021; 36:520-532. [PMID: 33674131 DOI: 10.1016/j.tree.2021.02.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2020] [Revised: 01/29/2021] [Accepted: 02/02/2021] [Indexed: 01/18/2023]
Abstract
Widespread tree mortality following droughts has emerged as an environmentally and economically devastating 'ecological surprise'. It is well established that tree physiology is important in understanding drought-driven mortality; however, the accuracy of predictions based on physiology alone has been limited. We propose that complicating factors at two levels stymie predictions of drought-driven mortality: (i) organismal-level physiological and site factors that obscure understanding of drought exposure and vulnerability and (ii) community-level ecological interactions, particularly with biotic agents whose effects on tree mortality may reverse expectations based on stress physiology. We conclude with a path forward that emphasizes the need for an integrative approach to stress physiology and biotic agent dynamics when assessing forest risk to drought-driven morality in a changing climate.
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Puentes A, Zhao T, Lundborg L, Björklund N, Borg-Karlson AK. Variation in Methyl Jasmonate-Induced Defense Among Norway Spruce Clones and Trade-Offs in Resistance Against a Fungal and an Insect Pest. FRONTIERS IN PLANT SCIENCE 2021; 12:678959. [PMID: 34108985 PMCID: PMC8182065 DOI: 10.3389/fpls.2021.678959] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2021] [Accepted: 04/28/2021] [Indexed: 05/22/2023]
Abstract
An essential component of plant defense is the change that occurs from a constitutive to an induced state following damage or infection. Exogenous application of the plant hormone methyl jasmonate (MeJA) has shown great potential to be used as a defense inducer prior to pest exposure, and could be used as a plant protection measure. Here, we examined (1) the importance of MeJA-mediated induction for Norway spruce (Picea abies) resistance against damage by the pine weevil Hylobius abietis, which poses a threat to seedling survival, and infection by the spruce bark beetle-associated blue-stain fungus Endoconidiophora polonica, (2) genotypic variation in MeJA-induced defense (terpene chemistry), and (3) correlations among resistance to each pest. In a semi-field experiment, we exposed rooted-cuttings from nine different Norway spruce clones to insect damage and fungal infection separately. Plants were treated with 0, 25, or 50 mM MeJA, and planted in blocks where only pine weevils were released, or in a separate block in which plants were fungus-inoculated or not (control group). As measures of resistance, stem area debarked and fungal lesion lengths were assessed, and as a measure of defensive capacity, terpene chemistry was examined. We found that MeJA treatment increased resistance to H. abietis and E. polonica, but effects varied with clone. Norway spruce clones that exhibited high constitutive resistance did not show large changes in area debarked or lesion length when MeJA-treated, and vice versa. Moreover, insect damage negatively correlated with fungal infection. Clones receiving little pine weevil damage experienced larger lesion lengths, and vice versa, both in the constitutive and induced states. Changes in absolute terpene concentrations occurred with MeJA treatment (but not on proportional terpene concentrations), however, variation in chemistry was mostly explained by differences between clones. We conclude that MeJA can enhance protection against H. abietis and E. polonica, but the extent of protection will depend on the importance of constitutive and induced resistance for the Norway spruce clone in question. Trade-offs among resistances do not necessarily hinder the use of MeJA, as clones that are constitutively more resistant to either pest, should show greater MeJA-induced resistance against the other.
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Affiliation(s)
- Adriana Puentes
- Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden
- *Correspondence: Adriana Puentes, ;
| | - Tao Zhao
- Man-Technology-Environment Research Centre, Örebro University, Örebro, Sweden
| | - Lina Lundborg
- Department of Chemistry, Organic Chemistry, KTH, Royal Institute of Technology, School of Chemical Science and Engineering, Stockholm, Sweden
| | - Niklas Björklund
- Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden
| | - Anna-Karin Borg-Karlson
- Department of Chemistry, Organic Chemistry, KTH, Royal Institute of Technology, School of Chemical Science and Engineering, Stockholm, Sweden
- Department of Chemical Engineering, Mid Sweden University, Sundsvall, Sweden
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