International Journal of Molecular Sciences

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12 pages, 12058 KiB

Open AccessArticle

Unravelling the Complexity of Plant Defense Induced by a Simultaneous and Sequential Mite and Aphid Infestation

by Małgorzata Kiełkiewicz, Anna Barczak-Brzyżek, Barbara Karpińska and Marcin Filipecki

Int. J. Mol. Sci. 2019, 20(4), 806; https://doi.org/10.3390/ijms20040806 - 13 Feb 2019

Cited by 8 | Viewed by 3498

Abstract

In natural and agricultural conditions, plants are attacked by a community of herbivores, including aphids and mites. The green peach aphid and the two-spotted spider mite, both economically important pests, may share the same plant. Therefore, an important question arises as to how [...] Read more.

In natural and agricultural conditions, plants are attacked by a community of herbivores, including aphids and mites. The green peach aphid and the two-spotted spider mite, both economically important pests, may share the same plant. Therefore, an important question arises as to how plants integrate signals induced by dual herbivore attack into the optimal defensive response. We showed that regardless of which attacker was first, 24 h of infestation allowed for efficient priming of the Arabidopsis defense, which decreased the reproductive performance of one of the subsequent herbivores. The expression analysis of several defense-related genes demonstrated that the individual impact of mite and aphid feeding spread systematically, engaging the salicylic acid (SA) and jasmonic acid (JA) signaling pathways. Interestingly, aphids feeding on the systemic leaf of the plant simultaneously attacked by mites, efficiently reduced the magnitude of the SA and JA activation, whereas mites feeding remotely increased the aphid-induced SA marker gene expression, while the JA-dependent response was completely abolished. We also indicated that the weaker performance of mites and aphids in double infestation essays might be attributed to aliphatic glucosinolates. Our report is the first to provide molecular data on signaling cross-talk when representatives of two distinct taxonomical classes within the phylum Arthropoda co-infest the same plant. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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17 pages, 2579 KiB

Open AccessArticle

Neonicotinoid Insecticides Alter the Transcriptome of Soybean and Decrease Plant Resistance

by Jason A. Wulff, Mahnaz Kiani, Karly Regan, Micky D. Eubanks and Adrianna Szczepaniec

Int. J. Mol. Sci. 2019, 20(3), 783; https://doi.org/10.3390/ijms20030783 - 12 Feb 2019

Cited by 24 | Viewed by 5320

Abstract

Neonicotinoids are widely used systemic insecticides that have been associated with spider mite outbreaks on diverse plants. These insecticides have complex effects on plant physiology, which have been speculated to drive enhanced performance of spider mites. We used RNA-Seq to explore how neonicotinoids [...] Read more.

Neonicotinoids are widely used systemic insecticides that have been associated with spider mite outbreaks on diverse plants. These insecticides have complex effects on plant physiology, which have been speculated to drive enhanced performance of spider mites. We used RNA-Seq to explore how neonicotinoids modify gene expression in soybean thereby lowering plant resistance. We exposed soybean (Glycine max L.) to two neonicotinoid insecticides, thiamethoxam applied to seeds and imidacloprid applied as a soil drench, and we exposed a subset of these plants to spider mites (Tetranychus cinnabarinus). Applications of both insecticides downregulated genes involved in plant—pathogen interactions, phytohormone pathways, phenylpropanoid pathway, and cell wall biosynthesis. These effects were especially pronounced in plants exposed to thiamethoxam. Introduction of spider mites restored induction of genes in these pathways in plants treated with imidacloprid, while expression of genes involved in phenylpropanoid synthesis, in particular, remained downregulated in thiamethoxam-treated plants. Our outcomes indicate that both insecticides suppress genes in pathways relevant to plant–arthropod interactions, and suppression of genes involved in cell wall synthesis may explain lower plant resistance to spider mites, cell-content feeders. These effects appear to be particularly significant when plants are exposed to neonicotinoids applied to soybean seeds. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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13 pages, 3158 KiB

Open AccessArticle

Expressing Double-Stranded RNAs of Insect Hormone-Related Genes Enhances Baculovirus Insecticidal Activity

by Zheming Liu, Xiaofang Wang, Yan Dai, Xiaoli Wei, Mi Ni, Lei Zhang and Zhen Zhu

Int. J. Mol. Sci. 2019, 20(2), 419; https://doi.org/10.3390/ijms20020419 - 18 Jan 2019

Cited by 5 | Viewed by 3807

Abstract

Baculoviruses have already been used for insect pest control, but the slow killing speed limits their further promotion and application. Here we provide a strategy for improving baculovirus insecticidal activity using Helicoverpa armigera nucleopolyhedrovirus (HearNPV) to express double-stranded RNAs (dsRNAs) targeting cotton bollworm [...] Read more.

Baculoviruses have already been used for insect pest control, but the slow killing speed limits their further promotion and application. Here we provide a strategy for improving baculovirus insecticidal activity using Helicoverpa armigera nucleopolyhedrovirus (HearNPV) to express double-stranded RNAs (dsRNAs) targeting cotton bollworm (Helicoverpa armigera) juvenile hormone (JH)-related genes. Droplet-feeding bioassays show that the 50% lethal concentration (LC₅₀) values of recombinant baculoviruses expressing the dsRNA of JH acid methyl transferase gene (HaJHAMT) and the JH acid binding protein gene (HaJHBP) were 1.24 × 10⁴ polyhedral inclusion bodies (PIB)/mL and 2.26 × 10⁴ PIB/mL, respectively. Both were much lower than the control value (8.12 × 10⁴ PIB/mL). Meanwhile, the LT₅₀ of recombinant baculovirus expressing dsRNA of HaJHBP was only 54.2% of the control value, which means that larval death was accelerated. Furthermore, the mRNA level of target genes was reduced in recombinant baculovirus-treated cotton bollworm larvae. Transcription of several key genes involved in hormone signaling pathways—for example, ecdysone receptor gene (HaEcR)—was also altered. This study establishes a new strategy for pest management by interfering with insect hormone-related gene expression via baculoviruses, and the engineered baculoviruses have great potential application in cotton production. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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20 pages, 1559 KiB

Open AccessArticle

Divergence in Glucosinolate Profiles between High- and Low-Elevation Populations of Arabidopsis halleri Correspond to Variation in Field Herbivory and Herbivore Behavioral Preferences

by James Buckley, Foteini G. Pashalidou, Martin C. Fischer, Alex Widmer, Mark C. Mescher and Consuelo M. De Moraes

Int. J. Mol. Sci. 2019, 20(1), 174; https://doi.org/10.3390/ijms20010174 - 5 Jan 2019

Cited by 11 | Viewed by 5720

Abstract

Variation in local herbivore pressure along elevation gradients is predicted to drive variation in plant defense traits. Yet, the extent of intraspecific variation in defense investment along elevation gradients, and its effects on both herbivore preference and performance, remain relatively unexplored. Using populations [...] Read more.

Variation in local herbivore pressure along elevation gradients is predicted to drive variation in plant defense traits. Yet, the extent of intraspecific variation in defense investment along elevation gradients, and its effects on both herbivore preference and performance, remain relatively unexplored. Using populations of Arabidopsis halleri (Brassicaceae) occurring at different elevations in the Alps, we tested for associations between elevation, herbivore damage in the field, and constitutive chemical defense traits (glucosinolates) assayed under common-garden conditions. Additionally, we examined the feeding preferences and performance of a specialist herbivore, the butterfly Pieris brassicae, on plants from different elevations in the Alps. Although we found no effect of elevation on the overall levels of constitutive glucosinolates in leaves, relative amounts of indole glucosinolates increased significantly with elevation and were negatively correlated with herbivore damage in the field. In oviposition preference assays, P. brassicae females laid fewer eggs on plants from high-elevation populations, although larval performance was similar on populations from different elevations. Taken together, these results support the prediction that species distributed along elevation gradients exhibit genetic variation in chemical defenses, which can have consequences for interactions with herbivores in the field. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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19 pages, 5142 KiB

Open AccessArticle

We Are What We Eat: A Stoichiometric and Ecometabolomic Study of Caterpillars Feeding on Two Pine Subspecies of Pinus sylvestris

by Albert Rivas-Ubach, Josep Peñuelas, José Antonio Hódar, Michal Oravec, Ljiljana Paša-Tolić, Otmar Urban and Jordi Sardans

Int. J. Mol. Sci. 2019, 20(1), 59; https://doi.org/10.3390/ijms20010059 - 24 Dec 2018

Cited by 10 | Viewed by 5366

Abstract

Many studies have addressed several plant-insect interaction topics at nutritional, molecular, physiological, and evolutionary levels. However, it is still unknown how flexible the metabolism and the nutritional content of specialist insect herbivores feeding on different closely related plants can be. We performed elemental, [...] Read more.

Many studies have addressed several plant-insect interaction topics at nutritional, molecular, physiological, and evolutionary levels. However, it is still unknown how flexible the metabolism and the nutritional content of specialist insect herbivores feeding on different closely related plants can be. We performed elemental, stoichiometric, and metabolomics analyses on leaves of two coexisting Pinus sylvestris subspecies and on their main insect herbivore; the caterpillar of the processionary moth (Thaumetopoea pityocampa). Caterpillars feeding on different pine subspecies had distinct overall metabolome structure, accounting for over 10% of the total variability. Although plants and insects have very divergent metabolomes, caterpillars showed certain resemblance to their plant-host metabolome. In addition, few plant-related secondary metabolites were found accumulated in caterpillar tissues which could potentially be used for self-defense. Caterpillars feeding on N and P richer needles had lower N and P tissue concentration and higher C:N and C:P ratios, suggesting that nutrient transfer is not necessarily linear through trophic levels and other plant-metabolic factors could be interfering. This exploratory study showed that little chemical differences between plant food sources can impact the overall metabolome of specialist insect herbivores. Significant nutritional shifts in herbivore tissues could lead to larger changes of the trophic web structure. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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21 pages, 2779 KiB

Open AccessArticle

Differential Responses of OsMPKs in IR56 Rice to Two BPH Populations of Different Virulence Levels

by Satyabrata Nanda, Pin-Jun Wan, San-Yue Yuan, Feng-Xiang Lai, Wei-Xia Wang and Qiang Fu

Int. J. Mol. Sci. 2018, 19(12), 4030; https://doi.org/10.3390/ijms19124030 - 13 Dec 2018

Cited by 18 | Viewed by 4731

Abstract

The conserved mitogen-activated protein kinase (MAPK) cascades play vital roles in plant defense responses against pathogens and insects. In the current study, the expression profiles of 17 OsMPKs were determined in the TN1 and IR56 rice varieties under the infestation of brown [...] Read more.

The conserved mitogen-activated protein kinase (MAPK) cascades play vital roles in plant defense responses against pathogens and insects. In the current study, the expression profiles of 17 OsMPKs were determined in the TN1 and IR56 rice varieties under the infestation of brown planthopper (BPH), one of the most destructive hemimetabolous rice pests. The virulent IR56 BPH population (IR56-BPH) and the avirulent TN1 BPH population (TN-BPH) were used to reveal the roles of OsMPKs in the compatible (IR56-BPH infested on the TN1 and IR56 rice varieties, and TN1-BPH infested on the TN1 rice variety) and the incompatible (TN1-BPH infested on the IR56 rice variety) interaction. The statistical analysis revealed that rice variety, BPH population type, and infestation period have significant effects on the transcription of OsMPKs. Out of these genes, five OsMPKs (OsMPK1, OsMPK3, OsMPK7, OsMPK14, and OsMPK16) were found to exhibit upregulated expression only during incompatible interaction. Six OsMPKs (OsMPK4, OsMPK5, OsMPK8, OsMPK9, OsMPK12, and OsMPK13) were associated with both incompatible and compatible interactions. The transcription analysis of salicylic acid, jasmonic acid, and ethylene phytohormone signaling genes revealed their roles during the rice–BPH interactions. The upregulated expression of OsC4H, OsCHS, and OsCHI in the incompatible interaction implied the potential defense regulatory roles of phenylpropanoids. In both varieties, the elevated transcript accumulations of OsGST and OsSOD, and the increased enzyme activities of POD, SOD, and GST at 1 day post-infestation (dpi), but not at 3 dpi, indicated that reactive oxygen species (ROS) signaling might be an early event in rice–BPH interactions. Furthermore, upregulated transcription of OsLecRK3 and OsLecRK4 was found only during an incompatible interaction, suggesting their involvement in the BPH resistance response in the IR56 rice variety. Lastly, based on the findings of this study, we have proposed a model of interactions of IR56 rice with TN1-BPH and IR56-BPH that depicts the resistance and susceptibility reactions, respectively. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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28 pages, 2804 KiB

Open AccessArticle

Oviposition by Spodoptera exigua on Solanum dulcamara Alters the Plant’s Response to Herbivory and Impairs Larval Performance

by Daniel Geuss, Tobias Lortzing, Jens Schwachtje, Joachim Kopka and Anke Steppuhn

Int. J. Mol. Sci. 2018, 19(12), 4008; https://doi.org/10.3390/ijms19124008 - 12 Dec 2018

Cited by 12 | Viewed by 5478

Abstract

Plant resistance traits against insect herbivores are extremely plastic. Plants respond not only to the herbivory itself, but also to oviposition by herbivorous insects. How prior oviposition affects plant responses to larval herbivory is largely unknown. Combining bioassays and defense protein activity assays [...] Read more.

Plant resistance traits against insect herbivores are extremely plastic. Plants respond not only to the herbivory itself, but also to oviposition by herbivorous insects. How prior oviposition affects plant responses to larval herbivory is largely unknown. Combining bioassays and defense protein activity assays with microarray analyses and metabolite profiling, we investigated the impact of preceding oviposition on the interaction of Solanum dulcamara with the generalist lepidopteran herbivore Spodoptera exigua at the levels of the plant’s resistance, transcriptome and metabolome. We found that oviposition increased plant resistance to the subsequent feeding larvae. While constitutive and feeding-induced levels of defensive protease inhibitor activity remained unaffected, pre-exposure to eggs altered S. dulcamara’s transcriptional and metabolic response to larval feeding in leaves local and systemic to oviposition. In particular, genes involved in phenylpropanoid metabolism were more strongly expressed in previously oviposited plants, which was reflected by reciprocal changes of primary metabolites upstream and within these pathways. Our data highlight that plants integrate signals from non-threatening life stages of their natural enemies to optimize their response when they become actually attacked. The observed transcriptional and metabolic reshaping of S. dulcamara’s response to S. exigua herbivory suggests a role of phenylpropanoids in oviposition-primed plant resistance. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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19 pages, 4896 KiB

Open AccessArticle

Overexpression of the Wild Soybean R2R3-MYB Transcription Factor GsMYB15 Enhances Resistance to Salt Stress and Helicoverpa Armigera in Transgenic Arabidopsis

by Xin-Jie Shen, Yan-Yan Wang, Yong-Xing Zhang, Wei Guo, Yong-Qing Jiao and Xin-An Zhou

Int. J. Mol. Sci. 2018, 19(12), 3958; https://doi.org/10.3390/ijms19123958 - 9 Dec 2018

Cited by 60 | Viewed by 5966

Abstract

Plant R2R3-MYB transcription factors (TFs) have been suggested to play crucial roles in the response to diverse abiotic and biotic stress factors but there is little molecular evidence of this role in soybean plants. In this work, we identified and functionally characterized an [...] Read more.

Plant R2R3-MYB transcription factors (TFs) have been suggested to play crucial roles in the response to diverse abiotic and biotic stress factors but there is little molecular evidence of this role in soybean plants. In this work, we identified and functionally characterized an R2R3-MYB TF, namely, GsMYB15, from the wild soybean ED059. Protein and promoter sequence analysis indicated that GsMYB15 is a typical R2R3-MYB TF and contains multiple stress-related cis-elements in the promoter region. GsMYB15 is located in the nucleus and exhibits transcriptional activation activity. QPCR assays suggested that the expression of GsMYB15 could be induced by NaCl, insect attacks and defense-related hormones (MeJA and SA). Furthermore, GsMYB15 exhibited highest expression in pods compared to other tissues. Functional analysis of GsMYB15 demonstrated that overexpression of GsMYB15 could increase salt tolerance and enhance the resistance to H. armigera larvae in transgenic Arabidopsis plants. Moreover, overexpression of GsMYB15 also affected the expression levels of salt stress- and defense-related genes in the transgenic plants. Feeding with transgenic Arabidopsis plant leaves could significantly suppress the expression levels of immunity-related genes in H. armigera larvae. Overexpression of GsMYB15 also increased mesophyll cell levels in transgenic plants. Taken together, these results provide evidence that GsMYB15 is a positive regulator of salt stress tolerance and insect resistance in transformed Arabidopsis plants. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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23 pages, 2546 KiB

Open AccessArticle

Interactive Responses of Solanum Dulcamara to Drought and Insect Feeding are Herbivore Species-Specific

by Duy Nguyen, Yvonne Poeschl, Tobias Lortzing, Rick Hoogveld, Andreas Gogol-Döring, Simona M. Cristescu, Anke Steppuhn, Celestina Mariani, Ivo Rieu and Nicole M. Van Dam

Int. J. Mol. Sci. 2018, 19(12), 3845; https://doi.org/10.3390/ijms19123845 - 3 Dec 2018

Cited by 13 | Viewed by 5035

Abstract

In nature, plants are frequently subjected to multiple biotic and abiotic stresses, resulting in a convergence of adaptive responses. We hypothesised that hormonal signalling regulating defences to different herbivores may interact with drought responses, causing distinct resistance phenotypes. To test this, we studied [...] Read more.

In nature, plants are frequently subjected to multiple biotic and abiotic stresses, resulting in a convergence of adaptive responses. We hypothesised that hormonal signalling regulating defences to different herbivores may interact with drought responses, causing distinct resistance phenotypes. To test this, we studied the hormonal and transcriptomic responses of Solanum dulcamara subjected to drought and herbivory by the generalist Spodoptera exigua (beet armyworm; BAW) or the specialist Leptinotarsa decemlineata (Colorado potato beetle; CPB). Bioassays showed that the performance of BAW, but not CPB, decreased on plants under drought compared to controls. While drought did not alter BAW-induced hormonal responses, it enhanced the CPB-induced accumulation of jasmonic acid and salicylic acid (SA), and suppressed ethylene (ET) emission. Microarray analyses showed that under drought, BAW herbivory enhanced several herbivore-induced responses, including cell-wall remodelling and the metabolism of carbohydrates, lipids, and secondary metabolites. In contrast, CPB herbivory enhanced several photosynthesis-related and pathogen responses in drought-stressed plants. This may divert resources away from defence production and increase leaf nutritive value. In conclusion, while BAW suffers from the drought-enhanced defences, CPB may benefit from the effects of enhanced SA and reduced ET signalling. This suggests that the fine-tuned interaction between the plant and its specialist herbivore is sustained under drought. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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19 pages, 1794 KiB

Open AccessArticle

Origanum vulgare Terpenoids Induce Oxidative Stress and Reduce the Feeding Activity of Spodoptera littoralis

by Chiara Agliassa and Massimo E. Maffei

Int. J. Mol. Sci. 2018, 19(9), 2805; https://doi.org/10.3390/ijms19092805 - 18 Sep 2018

Cited by 26 | Viewed by 5300

Abstract

Terpenoids are toxic compounds produced by plants as a defense strategy against insect herbivores. We tested the effect of Origanum vulgare terpenoids on the generalist herbivore Spodoptera littoralis and the response of the plant to herbivory. Terpenoids were analyzed by GC-FID and GC-MS [...] Read more.

Terpenoids are toxic compounds produced by plants as a defense strategy against insect herbivores. We tested the effect of Origanum vulgare terpenoids on the generalist herbivore Spodoptera littoralis and the response of the plant to herbivory. Terpenoids were analyzed by GC-FID and GC-MS and quantitative gene expression (qPCR) was evaluated on selected plant genes involved in both terpene biosynthesis. The insect detoxification response to terpenes was evaluated by monitoring antioxidant enzymes activity and expression of insect genes involved in terpene detoxification. O. vulgare terpenoid biosynthesis and gene expression was modulated by S. littoralis feeding. The herbivore-induced increased level of terpenoids (particularly carvacrol and p-cymene) interacted with the herbivore by decreasing larval survival and growth rate. The assimilation by S. littoralis of more than 50% of ingested terpenes correlated with the possible toxic effects of O. vulgare terpenoids. In choice test experiments, carvacrol and γ-terpinene mediated the larval feeding preferences, wherease the prolonged feeding on O. vulgare terpenoids (particularly on γ-terpinene) exerted relevant antinutritional effects on larvae. S. littoralis was found to react to O. vulgare terpenoids by increasing its antioxidant enzymes activities and gene expression, although this was not sufficient to sustain the toxicity of O. vulgare terpenoids. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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19 pages, 1831 KiB

Open AccessArticle

TPS Genes Silencing Alters Constitutive Indirect and Direct Defense in Tomato

by Mariangela Coppola, Pasquale Cascone, Simone Bossi, Giandomenico Corrado, Antonio Pietro Garonna, Massimo Maffei, Rosa Rao and Emilio Guerrieri

Int. J. Mol. Sci. 2018, 19(9), 2748; https://doi.org/10.3390/ijms19092748 - 13 Sep 2018

Cited by 8 | Viewed by 5444

Abstract

Following herbivore attacks, plants modify a blend of volatiles organic compounds (VOCs) released, resulting in the attraction of their antagonists. However, volatiles released constitutively may affect herbivores and natural enemies’ fitness too. In tomato there is still a lack of information on the [...] Read more.

Following herbivore attacks, plants modify a blend of volatiles organic compounds (VOCs) released, resulting in the attraction of their antagonists. However, volatiles released constitutively may affect herbivores and natural enemies’ fitness too. In tomato there is still a lack of information on the genetic bases responsible for the constitutive release of VOC involved in direct and indirect defenses. Here we studied the constitutive emissions related to the two most abundant sesquiterpene synthase genes expressed in tomato and their functional role in plant defense. Using an RNA interference approach, we silenced the expression of TPS9 and TPS12 genes and assessed the effect of this transformation on herbivores and parasitoids. We found that silenced plants displayed a different constitutive volatiles emission from controls, resulting in reduced attractiveness for the aphid parasitoid Aphidius ervi and in an impaired development of Spodoptera exigua larvae. We discussed these data considering the transcriptional regulation of key-genes involved in the pathway of VOC metabolism. We provide several lines of evidence on the metabolic flux from terpenoids to phenylpropanoids. Our results shed more light on constitutive defenses mediated by plant volatiles and on the molecular mechanisms involved in their metabolic regulation. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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15 pages, 4844 KiB

Open AccessArticle

Functional Characterization of An Allene Oxide Synthase Involved in Biosynthesis of Jasmonic Acid and Its Influence on Metabolite Profiles and Ethylene Formation in Tea (Camellia sinensis) Flowers

by Qiyuan Peng, Ying Zhou, Yinyin Liao, Lanting Zeng, Xinlan Xu, Yongxia Jia, Fang Dong, Jianlong Li, Jinchi Tang and Ziyin Yang

Int. J. Mol. Sci. 2018, 19(8), 2440; https://doi.org/10.3390/ijms19082440 - 18 Aug 2018

Cited by 20 | Viewed by 4815

Abstract

Jasmonic acid (JA) is reportedly involved in the interaction between insects and the vegetative parts of horticultural crops; less attention has, however, been paid to its involvement in the interaction between insects and the floral parts of horticultural crops. Previously, we investigated the [...] Read more.

Jasmonic acid (JA) is reportedly involved in the interaction between insects and the vegetative parts of horticultural crops; less attention has, however, been paid to its involvement in the interaction between insects and the floral parts of horticultural crops. Previously, we investigated the allene oxide synthase 2 (AOS2) gene that was found to be the only JA synthesis gene upregulated in tea (Camellia sinensis) flowers exposed to insect (Thrips hawaiiensis (Morgan)) attacks. In our present study, transient expression analysis in Nicotiana benthamiana plants confirmed that CsAOS2 functioned in JA synthesis and was located in the chloroplast membrane. In contrast to tea leaves, the metabolite profiles of tea flowers were not significantly affected by 10 h JA (2.5 mM) treatment as determined using ultra-performance liquid chromatography/quadrupole time-of-flight mass spectrometry, and gas chromatography-mass spectrometry. Moreover, JA treatment did not significantly influence ethylene formation in tea flowers. These results suggest that JA in tea flowers may have different functions from JA in tea leaves and other flowers. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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15 pages, 16459 KiB

Open AccessArticle

Molecular-Assisted Pollen Grain Analysis Reveals Spatiotemporal Origin of Long-Distance Migrants of a Noctuid Moth

by Hong Chang, Jianglong Guo, Xiaowei Fu, Yongqiang Liu, Kris A. G. Wyckhuys, Youming Hou and Kongming Wu

Int. J. Mol. Sci. 2018, 19(2), 567; https://doi.org/10.3390/ijms19020567 - 13 Feb 2018

Cited by 38 | Viewed by 7061

Abstract

Pollen grains are regularly used as markers to determine an insect’s movement patterns or host (plant) feeding behavior, yet conventional morphology-based pollen grain analysis (or palynology) encounters a number of important limitations. In the present study, we combine conventional analytical approaches with DNA [...] Read more.

Pollen grains are regularly used as markers to determine an insect’s movement patterns or host (plant) feeding behavior, yet conventional morphology-based pollen grain analysis (or palynology) encounters a number of important limitations. In the present study, we combine conventional analytical approaches with DNA meta-barcoding to identify pollen grains attached to migrating adults of the turnip moth, Agrotis segetum (Lepidoptera: Noctuidae) in Northeast China. More specifically, pollen grains were dislodged from 2566 A. segetum long-distance migrants captured on Beihuang Island (Bohai Sea) and identified to many (plant) species level. Pollen belonged to 26 families of plants, including Fagaceae, Oleaceae, Leguminosae, Asteraceae, Pinaceae and Rosaceae, including common species such as Citrus sinensis, Olea europaea, Ligustrum lucidum, Robinia pseudoacacia, Castanopsis echinocarpa, Melia azedarach and Castanea henryi. As the above plants are indigenous to southern climes, we deduce that A. segetum forage on plants in those locales prior to engaging in northward spring migration. Our work validates the use of DNA-assisted approaches in lepidopteran pollination ecology research and provides unique and valuable information on the adult feeding range and geographical origin of A. segetum. Our findings also enable targeted (area-wide) pest management interventions or guide the future isolation of volatile attractants. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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Review

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15 pages, 809 KiB

Open AccessReview

Morphological Complexity as a Floral Signal: From Perception by Insect Pollinators to Co-Evolutionary Implications

by Shivani Krishna and Tamar Keasar

Int. J. Mol. Sci. 2018, 19(6), 1681; https://doi.org/10.3390/ijms19061681 - 6 Jun 2018

Cited by 40 | Viewed by 6441

Abstract

Morphologically complex flowers are characterized by bilateral symmetry, tube-like shapes, deep corolla tubes, fused petals, and/or poricidal anthers, all of which constrain the access of insect visitors to floral nectar and pollen rewards. Only a subset of potential pollinators, mainly large bees, learn [...] Read more.

Morphologically complex flowers are characterized by bilateral symmetry, tube-like shapes, deep corolla tubes, fused petals, and/or poricidal anthers, all of which constrain the access of insect visitors to floral nectar and pollen rewards. Only a subset of potential pollinators, mainly large bees, learn to successfully forage on such flowers. Thus, complexity may comprise a morphological filter that restricts the range of visitors and thereby increases food intake for successful foragers. Such pollinator specialization, in turn, promotes flower constancy and reduces cross-species pollen transfer, providing fitness benefits to plants with complex flowers. Since visual signals associated with floral morphological complexity are generally honest (i.e., indicate food rewards), pollinators need to perceive and process them. Physiological studies show that bees detect distant flowers through long-wavelength sensitive photoreceptors. Bees effectively perceive complex shapes and learn the positions of contours based on their spatial frequencies. Complex flowers require long handling times by naive visitors, and become highly profitable only for experienced foragers. To explore possible pathways towards the evolution of floral complexity, we discuss cognitive mechanisms that potentially allow insects to persist on complex flowers despite low initial foraging gains, suggest experiments to test these mechanisms, and speculate on their adaptive value. Full article

(This article belongs to the Special Issue Plant-Insect Interactions 2018)

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