Soil food web components affect plant community structure during early succession

There is a growing awareness among ecologists of the strong links that exist between above- and belowground food webs. So far, the majority of studies have considered these links from the microbial point of view, usually with single plants or very simple plant communities. Here, we report the interactions between two components of the soil food web, root-feeding insects and arbuscular mycorrhizal (AM) fungi, and their effects on the structure and development of early successional plant communities. We use long-term field experiments that employ manipulations of these organisms, both singly and in combination. Both groups have strong effects on plant community structure, with root-feeding insects increasing and AM fungi decreasing plant species richness. Root-feeding insects appear to accelerate the process of early succession, while AM fungi retard it. There are strong interactions between the insects and fungi. The effect of insects is greatest when AM fungi are present. It is suggested that this is a consequence of plant physiology, rather than any direct interaction between the groups involved. Meanwhile, AM fungi have their greatest effect on plant communities when insects are absent, suggesting that there is some disruption of the symbiosis by the invertebrates. In developing plant communities, the rate and direction of the succession is therefore determined by the relative abundance of these two members of the soil food web. The next challenge will be to understand the roles of other members of the subterranean web in terms of their interactions with insects and AM fungi and effects on plant community development.     

Three-way interaction among plants,bacteria, and coleopteran insects

Main conclusion

Coleoptera, the largest and the most diverse Insecta order, is characterized by multiple adaptations to plant feeding. Insect-associated microorganisms can be important mediators and modulators of interactions between insects and plants. Interactions between plants and insects are highly complex and involve multiple factors. There are various defense mechanisms initiated by plants upon attack by herbivorous insects, including the development of morphological structures and the synthesis of toxic secondary metabolites and volatiles. In turn, herbivores have adapted to feeding on plants and further sophisticated adaptations to overcome plant responses may continue to evolve. Herbivorous insects may detoxify toxic phytocompounds, sequester poisonous plant factors, and alter their own overall gene expression pattern. Moreover, insects are associated with microbes, which not only considerably affect insects, but can also modify plant defense responses to the benefit of their host. Plants are also frequently associated with endophytes, which may act as bioinsecticides. Therefore, it is very important to consider the factors influencing the interaction between plants and insects. Herbivorous insects cause considerable damage to global crop production. Coleoptera is the largest and the most diverse order in the class Insecta. In this review, various aspects of the interactions among insects, microbes, and plants are described with a focus on coleopteran species, their bacterial symbionts, and their plant hosts to demonstrate that many factors contribute to the success of coleopteran herbivory.

     

植物与植食性昆虫化学互作研究进展

植物与植食性昆虫之间存在着复杂的化学相互作用。一方面,当遭受植食性昆虫为害时,植物能识别植食性昆虫相关分子模式,触发早期信号事件和激素信号转导途径,并由此引起转录组与代谢组重组、直接和间接防御化合物含量升高,最后提高对植食性昆虫的抗性。另一方面,植食性昆虫也能识别植物的防御反应,并能通过分泌效应子、选贮、解毒以及降低敏感性等反防御措施抑制或适应植物的化学防御。深入剖析植物与植食性昆虫的化学互作,不仅可在理论上丰富对昆虫与植物互作关系的理解,而且可在实践上为作物害虫防控新技术的开发提供重要的理论与技术指导。     

媒介昆虫-病毒-植物互作对生物入侵的影响

媒介昆虫-病毒-植物互作关系复杂多样。虽然相关的研究较多, 然而有关三者互作对于生物入侵的影响还知之甚少。已有证据表明, 寄主植物对病毒的敏感性和对媒介昆虫的适合性、媒介昆虫对寄主的适应能力等因素影响三者互作关系。当寄主植物易感病并且对媒介昆虫的适合性低, 而媒介昆虫对寄主植物的适应能力强时, 媒介昆虫与植物病毒之间很可能建立间接互惠关系, 这种互惠可促进媒介昆虫入侵和病毒病流行。此外, 媒介昆虫与植物病毒之间中性或偏害的互作关系对于外来生物入侵的促进作用也不容忽视。鉴于三者互作对于生物入侵的重要性, 今后需要对不同物种所组成的多种组合进行比较研究, 并采用多种方法揭示互作的生理和分子机制。     

唾液成分在刺吸式昆虫与植物关系中的作用

近年来,人们对刺吸式昆虫唾液成分的研究,揭示出其在刺吸式昆虫与植物关系中的重要作用。对多数刺吸式昆虫而言,他们取食时会分泌胶状和水状两种唾液,其中胶状唾液会在取食早期分泌形成唾液鞘来围绕并保护口针,通过直接和间接的作用来帮助取食;而水状唾液中则包含了果胶酶、纤维素酶、多酚氧化酶、过氧化物酶、碱性磷酸酯酶、蔗糖酶等组分,来帮助刺吸式昆虫对植物穿刺、消化食物、解毒次生物质并破坏植物的防御反应。有趣的是,唾液成分同时还可以诱导植物的防御反应,包括诱导植物的伤信号引起直接防御反应和诱导植物产生挥发物吸引植食者的天敌引起间接防御反应。并且,许多刺吸式昆虫取 食能够特异性地引发植物的病理反应,有研究推测刺吸式昆虫唾液中多聚半乳糖醛酸酶、碱性磷酸酯酶、蔗糖酶、多酚氧化酶等成分可能是某些植物特定病理反应的激发子,但是目前还没有定论,同时许多刺吸式昆虫唾液中的氨基酸和蛋白酶还是引起植物虫瘿的原因之一。 迄今的研究表明,刺吸式昆虫会根据不同的寄主植物和不同的生理需要,通过唾液组分的改变,来达到取食和发育的目的。对刺吸式昆虫唾液成分和作用机理的研究,可以为揭示刺吸式昆虫致害机理特别是传毒机理、指导害虫有效治理、阐明其与植物的协同进化等提供一定的思路。     

Plant scent and plant–insect interactions—Review and outlook from a macroevolutionary perspective

The astonishing diversity of plants and insects and their entangled interactions are cornerstones in terrestrial ecosystems. Co-occurring with species diversity is the diversity of plant secondary metabolites (PSMs). So far, their estimated number is more than 200 000 compounds, which are not directly involved in plant growth and development but play important roles in helping plants handle their environment including the mediation of plant–insect interactions. Here, we use plant volatile organic compounds (VOCs), a key olfactory communication channel that mediates plant–insect interactions, as a showcase of PSMs. In spite of the cumulative knowledge of the functional, ecological, and microevolutionary roles of VOCs, we still lack a macroevolutionary understanding of how they evolved with plant–insect interactions and contributed to species diversity throughout the long coevolutionary history of plants and insects. We first review the literature to summarize the current state-of-the-art research on this topic. We then present various relevant types of phylogenetic methods suitable to answer macroevolutionary questions on plant VOCs and suggest future directions for employing phylogenetic approaches in studying plant VOCs and plant–insect interactions. Overall, we found that current studies in this field are still very limited in their macroevolutionary perspective. Nevertheless, with the fast-growing development of metabolome analysis techniques and phylogenetic methods, it is becoming increasingly feasible to integrate the advances of these two areas. We highlight promising approaches to generate new testable hypotheses and gain a mechanistic understanding of the macroevolutionary roles of chemical communication in plant–insect interactions.     

论昆虫与植物的相互作用和进化的关系

昆虫与植物是陆地生物群落中最为重要的组成部分,二者间的相互作用是多方面的,其中最为重要的是昆虫选择植物作为食物和生长场所、昆虫为植物传授花粉两方面。该文集中讨论这两方面的相互作用有哪些因素与进化有密切的关系。植食性昆虫根据其寄主植物范围,通常分为专食性（寄主范围窄）和广食性（寄主范围广）。从生态关系来看,广食性的取食行为比专食性的更为有利,但实际情况却与此相反,统观植食性昆虫的取食行为,有向专食性演化更为普遍的倾向。专食性发展有利于提高昆虫对寄主植物的选择效率,还可缓和天敌作用所造成的压力。根据昆虫与植物相互作用的特点,目前已提出很多昆虫与植物的进化理论,包括成对的协同进化、弥散的协同进化、群落的协同进化以及顺序进化。在昆虫对寄主植物的选择中,以植物对昆虫的影响较昆虫对植物的影响更为重要,称为顺序进化是适宜的;昆虫为被子植物传授花粉造成互惠共生,其中的进化关系应称为协同进化。     

Legacy effects of aboveground-belowground interactions

Root herbivory can greatly affect the performance of aboveground insects via changes in plant chemistry. These interactions have been studied extensively in experiments where aboveground and belowground insects were feeding on the same plant. However, little is known about how aboveground and belowground organisms interact when they feed on plant individuals that grow after each other in the same soil. We show that feeding by aboveground and belowground insect herbivores on ragwort (Jacobaea vulgaris) plants exert unique soil legacy effects, via herbivore-induced changes in the composition of soil fungi. These changes in the soil biota induced by aboveground and belowground herbivores of preceding plants greatly influenced the pyrrolizidine alkaloid content, biomass and aboveground multitrophic interactions of succeeding plants. We conclude that plant-mediated interactions between aboveground and belowground insects are also important when they do not feed simultaneously on the same plant.     

植食性昆虫唾液效应子和激发子的研究进展

植食性昆虫与寄主植物通过协同进化形成了复杂的防御和反防御机制.本文系统综述了昆虫唾液效应子和激发子在植物与昆虫互作中的作用及机理.昆虫取食中释放的唾液激发子被植物识别而激活植物早期免疫反应,昆虫也能从口腔分泌效应子到植物体内抑制免疫;抗性植物则利用抗性(R)蛋白识别昆虫无毒效应子,启动效应子诱导的免疫反应,而昆虫又进化...     

Integration of alien plants into a native flower-pollinator visitation web

Introduced alien species influence many ecosystem services, including pollination of plants by animals. We extend the scope of recent 'single species' studies by analysing how alien plant species integrate themselves into a native flower visitation web. Historical records for a community in central USA show that 456 plant species received visits from 1429 insect and 1 hummingbird species, yielding 15 265 unique interactions. Aliens comprised 12.3% of all plant species, whereas only a few insects were alien. On average, the flowers of alien plants were visited by significantly fewer animal species than those of native plants. Most of these visitors were generalists, visiting many other plant species. The web of interactions between flowers and visitors was less richly connected for alien plants than for natives; nonetheless, aliens were well integrated into the native web. Because most visitors appear to be pollinators, this integration implies possible competitive and facilitative interactions between native and alien plants, mediated through animal visitors to flowers.     

Misleading herbivory in a tropical tree

The damage caused by herbivores can be confused with the drop of necrotic spots due to hypersensitive reactions. The negative impact of sessile herbivores on host plants is minimized by hypersensitive reactions that result in the death of attacked tissue. We reported a phenomenon that remarkably resembles herbivore damage, but is in fact a reaction to endophytic herbivores or pathogens. Although the damages on Tapirira guianensis leaves (Anacardiaceae) appear to be chew marks from herbivores, they are in fact dropped necrotic spots caused by gall-inducing insects. The phenomenon is widespread and challenges the view that gall-inducing insects inflict less damage on host plants, which was previously stated according to the rates of herbivory inflicted by free-feeding herbivores. The study highlights the need to reassess the past evaluations for some plant species, as they may have overestimated herbivory rates.     

植物多酚氧化酶的研究进展

多酚氧化酶(polyphenol oxidase,PPO)是一类普遍存在于植物、真菌和昆虫质体中,由核基因编码,能与铜相结合的金属蛋白酶.它能分别催化单酚羟基和二羟基酚氧化为O-二酚和O-醌.植物多酚氧化酶是许多果蔬等农产品酶促褐变的主要原因,同时它在植物的光合作用、抗病虫害、生长发育以及花色的形成中起一定作用.本文综述了植物多酚氧化酶在细胞学、分子遗传学及其生产应用等方面的研究进展.     

Bidirectional plant‐mediated interactions between rhizobacteria and shoot‐feeding herbivorous insects: a community ecology perspective

1. Plants interact with various organisms, aboveground as well as belowground. Such interactions result in changes in plant traits with consequences for members of the plant‐associated community at different trophic levels. Research thus far focussed on interactions of plants with individual species. However, studying such interactions in a community context is needed to gain a better understanding.
2. Members of the aboveground insect community induce defences that systemically influence plant interactions with herbivorous as well as carnivorous insects. Plant roots are associated with a community of plant‐growth promoting rhizobacteria (PGPR). This PGPR community modulates insect‐induced defences of plants. Thus, PGPR and insects interact indirectly via plant‐mediated interactions.
3. Such plant‐mediated interactions between belowground PGPR and aboveground insects have usually been addressed unidirectionally from belowground to aboveground. Here, we take a bidirectional approach to these cross‐compartment plant‐mediated interactions.
4. Recent studies show that upon aboveground attack by insect herbivores, plants may recruit rhizobacteria that enhance plant defence against the attackers. This rearranging of the PGPR community in the rhizosphere has consequences for members of the aboveground insect community. This review focusses on the bidirectional nature of plant‐mediated interactions between the PGPR and insect communities associated with plants, including (a) effects of beneficial rhizobacteria via modification of plant defence traits on insects and (b) effects of plant defence against insects on the PGPR community in the rhizosphere. We discuss how such knowledge can be used in the development of sustainable crop‐protection strategies.

     

植物多酚氧化酶的研究进展

多酚氧化酶(polyphenol oxidase, PPO)是一类普遍存在于植物、真菌和昆虫质体中,由核基因编码, 能与铜相结合的金属蛋白酶。它能分别催化单酚羟基和二羟基酚氧化为O-二酚和O-醌。植物多酚氧化酶是许多果蔬等农产品酶促褐变的主要原因, 同时它在植物的光合作用、抗病虫害、生长发育以及花色的形成中起一定作用。本文综述了植物多酚氧化酶在细胞学、分子遗传学及其生产应用等方面的研究进展。     

植物蛋白酶抑制剂在植物抗虫与抗病中的作用

综述了植物蛋白酶抑制剂抗虫与抗病作用的研究进展.蛋白酶抑制剂广泛存在于植物体内,与植物抗虫抗病密切相关.植物蛋白酶抑制剂能抑制昆虫肠道蛋白酶,使昆虫生长发育缓慢,甚至死亡.但取食蛋白酶抑制剂后,昆虫能迅速分泌对抑制剂不敏感的蛋白酶,而使蛋白酶抑制剂无效.食物蛋白的含量和质量也影响植物蛋白酶抑制剂的抗虫效果.病原菌的感染能诱导植物产生蛋白酶抑制剂,诱导产生的蛋白酶抑制剂能抑制病原菌的生长.     

P450s in plant-insect interactions

Cytochrome P450 monooxygenases (P450s) are integral in defining the relationships between plants and insects. Secondary metabolites produced in plants for protection against insects and other organisms are synthesized via pathways that include P450s in many different families and subfamilies. Survival of insects in the presence of toxic secondary metabolites depends on their metabolism by more limited groups of P450s. Examples of functionally characterized plant and insect P450s known to be involved in these interactions are discussed in terms of their diversities, reactivities and regulators. These and future examples, which will be uncovered as the fields of plant biology and entomology converge on this interesting area, provide much insight into the array of plant metabolites that are mainline defenses against insects, the range of insect monooxygenases that inactivate these compounds and the evolutionary processes occurring as these organisms wage daily battles with one another. Molecular perspectives on these interactions will provide the scientific community with information critical for genetic manipulation of these organisms aimed at enhancing plant resistance to insects and eliminating insect resistance to natural plant toxins and synthetic insecticides.     

Early progress in aphid genomics and consequences for plant-aphid interactions studies

Aphids occupy a niche comprising two conceptual realms: a micron-scale feeding site beneath the plant surface, in which a syringe-like appendage mediates chemical exchange with a specific plant cell type; and the larger realm of a metazoan with sensory organs, a nervous system, and behavior, all responsive to the condition of the host plant and the broader environment. The biology that connects these realms is not well understood, but new details are emerging with the help of genomic tools. The power of these tools is set to increase substantially now that the first genome of an aphid is being sequenced and annotated. This has been possible because a community of aphid researchers focused their efforts to develop and share genomic resources through an international consortium. This complete genome sequence, along with other resources, should permit major advances in understanding the complex and peculiar biological traits responsible for aphids' evolutionary success and their damaging effects on agriculture. This review highlights early progress in the application of aphid genomics and identifies key issues of plant-aphid interactions likely to benefit as molecular tools are further developed. Use of this new knowledge could make significant contributions to crop protection against these and other phloem-feeding insects.     

Invariant antagonistic network structure despite high spatial and temporal turnover of interactions

Recent work has suggested that emergent ecological network structure exhibits very little spatial or temporal variance despite changes in community composition. However, the changes in network interactions associated with turnover in community composition have seldom been assessed. Here we examine whether changes in ecological networks are best detected by standard emergent network metrics or by assessing internal network changes (i.e. interaction and composition turnover). To eliminate possible spatial or phylogenetic effects, that in large‐scale studies may obscure mechanisms structuring networks and interactions, we sampled multiple antagonistic (plant–herbivore) networks for a single diverse plant family (the Restionaceae) in the hyperdiverse Cape Floristic Region. These are the first plant–herbivore networks constructed for this global biodiversity hotspot. We found invariant emergent network structure despite considerable changes in insect and plant composition across communities over time and space. In contrast, there was high interaction turnover between networks. Seasonally, this was driven by turnover in insect species and insect host switching. Spatially, this was driven by simultaneous turnover in plant and insect species, suggesting that many insects are host specific or that both groups exhibit parallel responses to environmental gradients. Spatial interaction turnover was also driven by turnover in plants, showing that many insects can utilise multiple (possibly closely related) hosts and this may create divergent selection gradients that promote insect speciation. Thus we show highly variable interaction fidelity, despite invariant emergent network structure. We suggest that evaluating internal network changes may be more effective at elucidating the processes structuring networks, and many fine‐scale changes may be obscured when only calculating emergent network metrics.     

Perception of insect feeding by plants

The recognition of phytophagous insects by plants induces a set of very specific responses aimed at deterring tissue consumption and reprogramming metabolism and development of the plant to tolerate the herbivore. The recognition of insects by plants requires the plant’s ability to perceive chemical cues generated by the insects and to distinguish a particular pattern of tissue disruption. Relatively little is known about the molecular basis of insect perception by plants and the signalling mechanisms directly associated with this perception. Importantly, the insect feeding behaviour (piercing‐sucking versus chewing) is a decisive determinant of the plant’s defence response, and the mechanisms used to perceive insects from different feeding guilds may be distinct. During insect feeding, components of the saliva of chewing or piercing‐sucking insects come into contact with plant cells, and elicitors or effectors present in this insect‐derived fluid are perceived by plant cells to initiate the activation of specific signalling cascades. Although receptor–ligand interactions controlling insect perception have yet not been molecularly described, a significant number of regulatory components acting downstream of receptors and involved in the activation of defence responses against insects has been reported. Some of these regulators mediate changes in the phytohormone network, while others directly control gene expression or the redox state of the cell. These processes are central in the orchestration of plant defence responses against insects.     

Multiple calmodulin-like proteins in Arabidopsis are induced by insect-derived (Spodoptera littoralis) oral secretion

In plant cells, diverse environmental changes often induce transient elevation in the intracellular calcium concentrations, which are involved in signaling pathways leading to the respective cellular reactions. Therefore, these calcium elevations need to be deciphered into specific downstream responses. Calmodulin-like-proteins (CMLs) are calcium-sensing proteins present only in higher plants. They are involved in signaling processes induced by both abiotic as well as biotic stress factors. However, the role of CMLs in the interaction of plants with herbivorous insects is almost unknown. Here we show that in Arabidopsis thaliana a number of CMLs genes (CML9, 11,12,16,17 and 23) are upregulated due to treatments with oral secretion of larvae of the herbivorous insect Spodoptera littoralis. We identified that these genes belong to two groups that respond with different kinetics to the treatment with oral secretion. Our data indicate that signaling networks involving multiple CMLs very likely have important functions in plant defense against insect herbivores, in addition to their involvement in many other stress-induced processes in plants.