Focus on Metabolism: Posttranslational Protein Modifications in Plant Metabolism

Posttranslational modifications (PTMs) of proteins greatly expand proteome diversity, increase functionality, and allow for rapid responses, all at relatively low costs for the cell. PTMs play key roles in plants through their impact on signaling, gene expression, protein stability and interactions, and enzyme kinetics. Following a brief discussion of the experimental and bioinformatics challenges of PTM identification, localization, and quantification (occupancy), a concise overview is provided of the major PTMs and their (potential) functional consequences in plants, with emphasis on plant metabolism. Classic examples that illustrate the regulation of plant metabolic enzymes and pathways by PTMs and their cross talk are summarized. Recent large-scale proteomics studies mapped many PTMs to a wide range of metabolic functions. Unraveling of the PTM code, i.e. a predictive understanding of the (combinatorial) consequences of PTMs, is needed to convert this growing wealth of data into an understanding of plant metabolic regulation.The primary amino acid sequence of proteins is defined by the translated mRNA, often followed by N- or C-terminal cleavages for preprocessing, maturation, and/or activation. Proteins can undergo further reversible or irreversible posttranslational modifications (PTMs) of specific amino acid residues. Proteins are directly responsible for the production of plant metabolites because they act as enzymes or as regulators of enzymes. Ultimately, most proteins in a plant cell can affect plant metabolism (e.g. through effects on plant gene expression, cell fate and development, structural support, transport, etc.). Many metabolic enzymes and their regulators undergo a variety of PTMs, possibly resulting in changes in oligomeric state, stabilization/degradation, and (de)activation (Huber and Hardin, 2004), and PTMs can facilitate the optimization of metabolic flux. However, the direct in vivo consequence of a PTM on a metabolic enzyme or pathway is frequently not very clear, in part because it requires measurements of input and output of the reactions, including flux through the enzyme or pathway. This Update will start out with a short overview on the major PTMs observed for each amino acid residue (PTMs, including determination of the localization within proteins (i.e. the specific residues) and occupancy. Challenges in dealing with multiple PTMs per protein and cross talk between PTMs will be briefly outlined. We then describe the major physiological PTMs observed in plants as well as PTMs that are nonenzymatically induced during sample preparation (PTMs, in particular for enzymes in primary metabolism (Calvin cycle, glycolysis, and respiration) and the C4 shuttle accommodating photosynthesis in C4 plants (PTMs observed in plants

Effect of Herbivory and Plant Species Replacement on Primary Production

Grazing optimization occurs when herbivory increases primary production at low grazing intensities. In the case of simple plant-herbivore interactions, such an effect can result from recycling of a limiting nutrient. However, in more complex cases, herbivory can also lead to species replacement in plant communities, which in turn alters how primary production is affected by herbivory. Here we explore this issue using a model of a limiting nutrient cycle in an ecosystem with two plant species. We show that two major plant traits determine primary production at equilibrium: plant recycling efficiency (i.e., the fraction of the plant nutrient stock that stays within the ecosystem until it is returned to the nutrient pool in mineral form) and plant ability to deplete the soil mineral nutrient pool through consumption of this resource. In cases where sufficient time has occurred, grazing optimization requires that herbivory improve nutrient conservation in the system sufficiently. This condition sets a minimum threshold for herbivore nutrient recycling efficiency, the fraction of nutrient consumed by herbivores that is recycled within the ecosystem to the mineral nutrient pool. This threshold changes with plant community composition and herbivore preference and is, therefore, strongly affected by plant species replacement. The quantitative effects of these processes on grazing optimization are determined by both the recycling efficiencies and depletion abilities of the plant species. However, grazing optimization remains qualitatively possible even with plant species replacement.     

Herbivory and Stoichiometric Feedbacks to Primary Production

Established theory addresses the idea that herbivory can have positive feedbacks on nutrient flow to plants. Positive feedbacks likely emerge from a greater availability of organic carbon that primes the soil by supporting nutrient turnover through consumer and especially microbially-mediated metabolism in the detrital pool. We developed an entirely novel stoichiometric model that demonstrates the mechanism of a positive feedback. In particular, we show that sloppy or partial feeding by herbivores increases detrital carbon and nitrogen allowing for greater nitrogen mineralization and nutritive feedback to plants. The model consists of differential equations coupling flows among pools of: plants, herbivores, detrital carbon and nitrogen, and inorganic nitrogen. We test the effects of different levels of herbivore grazing completion and of the stoichiometric quality (carbon to nitrogen ratio, C:N) of the host plant. Our model analyses show that partial feeding and plant C:N interact because when herbivores are sloppy and plant biomass is diverted to the detrital pool, more mineral nitrogen is available to plants because of the stoichiometric difference between the organisms in the detrital pool and the herbivore. This model helps to identify how herbivory may feedback positively on primary production, and it mechanistically connects direct and indirect feedbacks from soil to plant production.     

Focus on Metabolism: Functional Divergence of Diterpene Syntheses in the Medicinal Plant Salvia miltiorrhiza

The medicinal plant Salvia miltiorrhiza produces various tanshinone diterpenoids that have pharmacological activities such as vasorelaxation against ischemia reperfusion injury and antiarrhythmic effects. Their biosynthesis is initiated from the general diterpenoid precursor (E,E,E)-geranylgeranyl diphosphate by sequential reactions catalyzed by copalyl diphosphate synthase (CPS) and kaurene synthase-like cyclases. Here, we report characterization of these enzymatic families from S. miltiorrhiza, which has led to the identification of unique pathways, including roles for separate CPSs in tanshinone production in roots versus aerial tissues (SmCPS1 and SmCPS2, respectively) as well as the unique production of ent-13-epi-manoyl oxide by SmCPS4 and S. miltiorrhiza kaurene synthase-like2 in floral sepals. The conserved SmCPS5 is involved in gibberellin plant hormone biosynthesis. Down-regulation of SmCPS1 by RNA interference resulted in substantial reduction of tanshinones, and metabolomics analysis revealed 21 potential intermediates, indicating a complex network for tanshinone metabolism defined by certain key biosynthetic steps. Notably, the correlation between conservation pattern and stereochemical product outcome of the CPSs observed here suggests a degree of correlation that, especially when combined with the identity of certain key residues, may be predictive. Accordingly, this study provides molecular insights into the evolutionary diversification of functional diterpenoids in plants.Salvia miltiorrhiza, a Lamiaceae species known as red sage or tanshen, is a traditional Chinese medicinal herb that is described in Shen Nong Ben Cao Jing, the oldest classical Chinese herbal book, which dates from between 25 and 220 C.E. The lipophilic pigments from the reddish root and rhizome consist of abietane quinone diterpenoids (Nakao and Fukushima, 1934), largely tanshinone IIA, cryptotanshinone, and tanshinone I (Zhong et al., 2009). These are highly bioactive. For example, tanshinone IIA exerts vasorelaxative activity, has antiarrhythmic effects, provides protection against ischemia reperfusion injury (Zhou et al., 2005; Gao et al., 2008; Sun et al., 2008), and exhibits anticancer activities (Efferth et al., 2008; Lee et al., 2008; Wang et al., 2008; Gong et al., 2011). In addition, tanshinones have been reported to have a broad spectrum of antimicrobial activities against various plant pathogens, including rice (Oryza sativa) blast fungus Magnaporthe oryzae (Zhao et al., 2011). Although tanshinones are mainly accumulated in the roots, trace amounts of tanshinones have been detected in aerial organs as well (Hang et al., 2008).Diterpenoid biosynthesis is initiated by diterpene synthases (diTPSs), which catalyze cyclization and/or rearrangement of the general acyclic precursor (E,E,E)-geranylgeranyl diphosphate (GGPP) to form various hydrocarbon backbone structures that are precursors to more specific families of diterpenoids (Zi et al., 2014). Previous work has indicated that tanshinone biosynthesis is initiated by cyclization of GGPP to copalyl diphosphate (CPP) by a CPP synthase (SmCPS1) and subsequent further cyclization to the abietane miltiradiene by a kaurene synthase-like cyclase (SmKSL1), so named for its homology to the ent-kaurene synthases (KSs) required for GA plant hormone biosynthesis (Gao et al., 2009). Miltiradiene is a precursor to at least cryptotanshinone (Guo et al., 2013), and RNA interference (RNAi) knockdown of SmCPS1 expression reduces tanshinone production, at least in hairy root cultures (Cheng et al., 2014). The identification of SmCPS1 and SmKSL1 has been followed by that of many related diTPSs from other Lamiaceae plant species (Caniard et al., 2012; Sallaud et al., 2012; Schalk et al., 2012; Brückner et al., 2014; Pateraki et al., 2014). These largely exhibit analogous activity, particularly the CPSs, which produce CPP or the stereochemically related 8α-hydroxy-labd-13E-en-15-yl diphosphate (LDPP) rather than the enantiomeric (ent) CPP relevant to GA biosynthesis.To further investigate diterpenoid biosynthesis in S. miltiorrhiza, we report here a more thorough characterization of its diTPS family. A previously reported whole-genome shotgun sequencing survey (Ma et al., 2012) has indicated that there are at least five CPSs, although only two KSL genes in S. miltiorrhiza (Supplemental Table S1). Intriguingly, based on a combination of biochemical and genetic (RNAi gene silencing) evidence, we find that these diTPSs nevertheless account for at least four different diterpenoid biosynthetic pathways, each dependent on a unique CPS, with the KS presumably involved in GA biosynthesis seeming to be responsible for alternative diterpenoid metabolism as well. In addition, our studies clarify the evolutionary basis for the observed functional diversity, with investigation of gene structure, positive selection, molecular docking, and mutational analysis used to explore the driving force for the functional divergence of these diTPSs. Moreover, we report metabolomic analysis, also carried out with SmCPS1 RNAi lines, which enables prediction of the downstream steps in tanshinone biosynthesis.     

Focus on Metabolism: Something Old,Something New: Conserved Enzymes and the Evolution of Novelty in Plant Specialized Metabolism

Plants produce hundreds of thousands of small molecules known as specialized metabolites, many of which are of economic and ecological importance. This remarkable variety is a consequence of the diversity and rapid evolution of specialized metabolic pathways. These novel biosynthetic pathways originate via gene duplication or by functional divergence of existing genes, and they subsequently evolve through selection and/or drift. Studies over the past two decades revealed that diverse specialized metabolic pathways have resulted from the incorporation of primary metabolic enzymes. We discuss examples of enzyme recruitment from primary metabolism and the variety of paths taken by duplicated primary metabolic enzymes toward integration into specialized metabolism. These examples provide insight into processes by which plant specialized metabolic pathways evolve and suggest approaches to discover enzymes of previously uncharacterized metabolic networks.The plant kingdom collectively produces hundreds of thousands of low molecular weight organic molecules traditionally known as secondary metabolites, some of which have been shown to play roles in abiotic and biotic stress responses (e.g. herbivory defense), beneficial insect interactions (e.g. pollinator attraction), and communication with other plant and nonplant species (e.g. allelopathy and legume-rhizobia interactions; Saito and Matsuda, 2010; Pichersky and Lewinsohn, 2011; Wink, 2011). These metabolites have been widely used throughout the course of human history as medicines, spices, perfumes, cosmetics, and pest-control agents as well as in religious and cultural rituals. For the past 150 years, there has been a strong focus on documenting the chemical diversity of secondary metabolites in the plant kingdom, leading to the discovery of diverse classes of compounds such as terpenes, flavonoids, alkaloids, phenylpropanoids, glucosinolates, and polyketides. These secondary compounds were historically differentiated from products of primary metabolism, such as sugars, amino acids, nucleic acids, and fatty acids, as being nonessential for plant survival (Sachs, 1874; Kossel, 1891; Hartmann, 2008). However, by the 1980s, important functional roles began to be elucidated for metabolites previously classified as secondary, such as the phenolics (e.g. plant-microbe interactions and UV-B light protection; Bolton et al., 1986; Peters et al., 1986; Li et al., 1993; Landry et al., 1995), alkaloids (defense against herbivory; Steppuhn et al., 2004), and terpenes (defense against herbivory, antimicrobial activities, and volatile pollinator attractants; Papadopoulou et al., 1999; Schiestl and Ayasse, 2001; Erbilgin et al., 2006; Nieuwenhuizen et al., 2009). This change in our understanding of their roles has led to the coining of a new term, specialized metabolites, for these compounds, both to acknowledge their importance and to reflect the fact that many of them are phylogenetically restricted (Pichersky et al., 2006; Pichersky and Lewinsohn, 2011).Although the structural diversity of specialized metabolites far exceeds that of primary metabolites, all specialized metabolite classes are ultimately derived from primary metabolic precursors (Wink, 2011). For example, phenylpropanoids are derived from the amino acid Phe (Vogt, 2010), while the biosynthetic blocks of terpenes, isopentenyl diphosphate and dimethylallyl diphosphate, originate from mevalonate, a sterol precursor, and alternatively from methylerythritol phosphate, which is derived from glycolytic pathway precursors (Kirby and Keasling, 2009). Nitrogen-containing alkaloids are derived from a variety of primary metabolites, including amino acids and purine nucleosides (Facchini, 2001). Over the past 20 years, an increasing number of specialized metabolic enzymes have also been found to have their origins in primary metabolic pathways (Weng, 2014). Such shifts in enzyme function are made possible primarily by the process of gene duplication, which is very common in plants.     

Focus on Water: Monitoring Plant Drought Stress Response Using Terahertz Time-Domain Spectroscopy

We present a novel measurement setup for monitoring changes in leaf water status using nondestructive terahertz time-domain spectroscopy (THz-TDS). Previous studies on a variety of plants showed the principal applicability of THz-TDS. In such setups, decreasing leaf water content directly correlates with increasing THz transmission. Our new system allows for continuous, nondestructive monitoring of the water status of multiple individual plants each at the same constant leaf position. It overcomes previous drawbacks, which were mainly due to the necessity of relocating the plants. Using needles of silver fir (Abies alba) seedlings as test subjects, we show that the transmission varies along the main axis of a single needle due to a variation in thickness. Therefore, the relocation of plants during the measuring period, which was necessary in the previous THz-TDS setups, should be avoided. Furthermore, we show a highly significant correlation between gravimetric water content and respective THz transmission. By monitoring the relative change in transmission, we were able to narrow down the permanent wilting point of the seedlings. Thus, we established groups of plants with well-defined levels of water stress that could not be detected visually. This opens up the possibility for a broad range of genetic and physiological experiments.Climate change simulations predict an increase in the occurrence of drought events in the Mediterranean area and in central Europe due to smaller amounts of precipitation, especially during summer periods (IPCC, 2007). With the exception of the boreal zone, this leads to an increase in drought risks for every region on the European continent (Iglesias et al., 2007). Water availability is very important for a variety of plant species. Trees and crops play major roles regarding ecosystem stability and food supply. Forest trees are keystone elements in shaping long-term, regional ecosystem composition and stability and are, like most forest species, highly vulnerable to increases in drought severity (Breshears et al., 2005; Choat et al., 2012). Drought-induced forest die-offs thereby directly reduce ecosystem services such as carbon sequestration and timber supply (Allen et al., 2010). Further research is clearly necessary to elucidate the physiological traits and responses of plants regarding their water status.European silver fir (Abies alba) is an important forest tree species of ecological and economic relevance. This study is embedded in the European project LinkTree, “linking genetic variability with ecological responses to environmental changes: forest trees as model systems.” Our group is concerned with the identification of genes involved in the water stress response of silver fir. This species is of special interest because of its lower water-use efficiency compared with other conifer species (Guehl and Aussenac, 1987; Guehl et al., 1991).For this purpose, monitoring plant water status without inducing other forms of stress is instrumental in order to apply well-defined levels of water stress. Obtaining information regarding the water status of a plant is highly problematic without using invasive and destructive methods that usually only allow a retrospective assessment. These include commonly established methods, such as the gravimetric water content and pressure chamber techniques, most notably Scholander’s pressure bomb (Scholander et al., 1965).Chlorophyll fluorescence, stomatal conductance, and visual assessment are examples of nondestructive and noninvasive measurement techniques. The former two only provide indirect information about the plant stress status and, therefore, the water content via photosynthetic activity (Lichtenthaler and Rinderle, 1988; Tardieu and Davies, 1993). The latter is difficult to standardize and highly dependent on the morphology of the studied plant species. Conifers especially are challenging subjects for visually assessing drought stress. Due to their needle morphology, it is nearly impossible to detect early signs of dehydration.Measurement techniques using electromagnetic radiation in the terahertz (THz) regime have shown promising results, due to the nondestructive nature and high sensitivity of THz waves to water. With THz waves, we refer to frequencies in the electromagnetic spectrum between 0.1 and 1 THz, corresponding to wavelengths between 3 and 0.3 mm, which are located between infrared light (thermal radiation) and microwave radiation (used in common wireless data communication systems). In the last decade, terahertz time-domain spectroscopy (THz-TDS) has proven to be a very strong and accurate tool for characterizing and imaging various materials (for review, see Jepsen et al., 2011). Crucial for our study is the remarkably high absorption coefficient of water in this part of the electromagnetic spectrum. Thus, it is a robust technique hardly affected by physiological concentrations of soluble substances. Using transmission geometry, the resulting absorption by plant tissues directly reflects the quantity of water molecules.Furthermore, THz-TDS does not suffer from the disadvantages of other radiation-based techniques. These are mainly focused on the infrared or microwave spectrum but either lack the sensitivity for small changes in leaf water status or are affected by the plant’s inorganic salt content, leading to significant disturbances (Ulaby and Jedlicka, 1984). Moreover, the applicability of emitting microwave radiation is limited to minimal wavelengths of approximately 2.5 mm. The Abbe diffraction limit, therefore, restricts the minimum diameter of a measurable object to approximately 1.25 mm. In order to measure small leaves, such as coniferous needles, electromagnetic radiation with shorter wavelengths is necessary.Although presenting a useful alternative, THz-TDS was not feasible until recently, due to the difficulty of generating and detecting electromagnetic radiation with wavelengths in the THz spectrum. Despite its promising applicability in plant sciences, until now this relatively novel method relied exclusively on measurement setups that allowed only a single measurement per alternating plant (Hadjiloucas et al., 1999; Jördens et al., 2009; Breitenstein et al., 2012; Castro-Camus et al., 2013; Gente et al., 2013). For the purpose of continuously monitoring multiple plants, these setups are only of limited use, since the plants must be relocated for every measurement. This results in two problems: (1) an increase in possible disturbances (e.g. mechanical), influencing the plant’s stress response, and (2) the necessity to precisely target the same measurement spot on every analyzed plant at every consecutive measurement. The latter is of crucial importance for the exact monitoring of any individual plant’s water status because, as we will show in this study, the transmission varies substantially across the area of plant leaf tissue.We present a novel measurement procedure that overcomes the drawbacks of previously proposed methods. Our approach enables us to precisely monitor changes in the water content of multiple plants simultaneously.In the course of this study, three different experiments were performed. The profile measurement and the rehydration experiment were preliminary investigations to examine the influences of needle and tissue thickness and to define a nonlethal stress level. The main experiment established groups of plants with comparable levels of water stress.     

Effects of Nitrogen Deposition on Insect Herbivory: Implications for Community and Ecosystem Processes

The deposition of anthropogenically fixed nitrogen (N) from the atmosphere onto land and plant surfaces has strong influences on terrestrial ecosystem processes. Although recent research has expanded our understanding of how N deposition affects ecosystems directly, less attention has been directed toward the investigation of how N deposition may affect ecosystems indirectly by modifying interactions among organisms. Empirical evidence suggests that there are several mechanisms by which N deposition may affect interactions between plants and insect herbivores. The most likely mechanisms are deposition-induced shifts in the quality and availability of host plant tissues. We discuss the effects of N deposition on host plant chemistry, production, and phenology, and we review the evidence for the effects of N deposition on insect herbivores at the individual, population, and community levels. In general, N deposition has positive effects on individual insect performance, probably due to deposition-induced improvements in host plant chemistry. These improvements include increased N and decreased carbon-based defensive compound concentrations. The evidence to date suggests that N deposition may also have a positive effect on insect populations. These effects may have considerable ecological, as well as economic consequences if the rates of herbivory on economically important timber species continue to increase. Deposition-induced changes in plant–herbivore relationships may affect community and ecosystem processes. However, we predict that the larger-scale consequences of interactions between N deposition and herbivory will vary based on site-specific factors. In addition, interactions between N deposition and other global-scale changes may lead to nonadditive effects on patterns of herbivory.     

植物抗虫性次生物质的研究概况

综述了国内外与植物抗虫性有关的次生物质的主要类型和植物次生物质对昆虫的寄主选择、取食和产卵等作用的研究进展,对次生物质在生态系统中的作用也作了介绍,并展望了植物次生物质的应用前景。     

De Novo Biosynthesis of Volatiles Induced by Insect Herbivory in Cotton Plants

In response to insect feeding on the leaves, cotton (Gossypium hirsutum L.) plants release elevated levels of volatiles, which can serve as a chemical signal that attracts natural enemies of the herbivore to the damaged plant. Pulse-labeling experiments with [13C]CO2 demonstrated that many of the volatiles released, including the acyclic terpenes (E,E)-[alpha]-farnesene, (E)-[beta]-farnesene, (E)-[beta]-ocimene, linalool, (E)-4,8-dimethyl-1,3,7-nonatriene, and (E/E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, as well as the shikimate pathway product indole, are biosynthesized de novo following insect damage. However, other volatile constituents, including several cyclic terpenes, butyrates, and green leaf volatiles of the lipoxygenase pathway are released from storage or synthesized from stored intermediates. Analysis of volatiles from artificially damaged plants, with and without beet armyworm (Spodoptera exigua Hubner) oral secretions exogenously applied to the leaves, as well as volatiles from beet armyworm-damaged and -undamaged control plants, demonstrated that the application of caterpillar oral secretions increased both the production and release of several volatiles that are synthesized de novo in response to insect feeding. These results establish that the plant plays an active and dynamic role in mediating the interaction between herbivores and natural enemies of herbivores.     

Drought and Root Herbivory Interact to Alter the Response of Above-Ground Parasitoids to Aphid Infested Plants and Associated Plant Volatile Signals

Multitrophic interactions are likely to be altered by climate change but there is little empirical evidence relating the responses of herbivores and parasitoids to abiotic factors. Here we investigated the effects of drought on an above/below-ground system comprising a generalist and a specialist aphid species (foliar herbivores), their parasitoids, and a dipteran species (root herbivore).We tested the hypotheses that: (1) high levels of drought stress and below-ground herbivory interact to reduce the performance of parasitoids developing in aphids; (2) drought stress and root herbivory change the profile of volatile organic chemicals (VOCs) emitted by the host plant; (3) parasitoids avoid ovipositing in aphids feeding on plants under drought stress and root herbivory. We examined the effect of drought, with and without root herbivory, on the olfactory response of parasitoids (preference), plant volatile emissions, parasitism success (performance), and the effect of drought on root herbivory. Under drought, percentage parasitism of aphids was reduced by about 40–55% compared with well watered plants. There was a significant interaction between drought and root herbivory on the efficacy of the two parasitoid species, drought stress partially reversing the negative effect of root herbivory on percent parasitism. In the absence of drought, root herbivory significantly reduced the performance (e.g. fecundity) of both parasitoid species developing in foliar herbivores. Plant emissions of VOCs were reduced by drought and root herbivores, and in olfactometer experiments parasitoids preferred the odour from well-watered plants compared with other treatments. The present work demonstrates that drought stress can change the outcome of interactions between herbivores feeding above- and below-ground and their parasitoids, mediated by changes in the chemical signals from plants to parasitoids. This provides a new insight into how the structure of terrestrial communities may be affected by drought.     

Floral Assemblages and Patterns of Insect Herbivory during the Permian to Triassic of Northeastern Italy

To discern the effect of the end-Permian (P-Tr) ecological crisis on land, interactions between plants and their insect herbivores were examined for four time intervals containing ten major floras from the Dolomites of northeastern Italy during a Permian–Triassic interval. These floras are: (i) the Kungurian Tregiovo Flora; (ii) the Wuchiapingian Bletterbach Flora; (iii) three Anisian floras; and (iv) five Ladinian floras. Derived plant–insect interactional data is based on 4242 plant specimens (1995 Permian, 2247 Triassic) allocated to 86 fossil taxa (32 Permian, 56 Triassic), representing lycophytes, sphenophytes, pteridophytes, pteridosperms, ginkgophytes, cycadophytes and coniferophytes from 37 million-year interval (23 m.yr. Permian, 14 m.yr. Triassic). Major Kungurian herbivorized plants were unaffiliated taxa and pteridosperms; later during the Wuchiapingian cycadophytes were predominantly consumed. For the Anisian, pteridosperms and cycadophytes were preferentially consumed, and subordinately pteridophytes, lycophytes and conifers. Ladinian herbivores overwhelming targeted pteridosperms and subordinately cycadophytes and conifers. Throughout the interval the percentage of insect-damaged leaves in bulk floras, as a proportion of total leaves examined, varied from 3.6% for the Kungurian (N = 464 leaves), 1.95% for the Wuchiapingian (N = 1531), 11.65% for the pooled Anisian (N = 1324), to 10.72% for the pooled Ladinian (N = 923), documenting an overall herbivory rise. The percentage of generalized consumption, equivalent to external foliage feeding, consistently exceeded the level of specialized consumption from internal feeding. Generalized damage ranged from 73.6% (Kungurian) of all feeding damage, to 79% (Wuchiapingian), 65.5% (pooled Anisian) and 73.2% (pooled Ladinian). Generalized-to-specialized ratios show minimal change through the interval, although herbivore component community structure (herbivore species feeding on a single plant-host species) increasingly was partitioned from Wuchiapingian to Ladinian. The Paleozoic plant with the richest herbivore component community, the coniferophyte Pseudovoltzia liebeana, harbored four damage types (DTs), whereas its Triassic parallel, the pteridosperm Scytophyllum bergeri housed 11 DTs, almost four times that of P. liebeana. Although generalized DTs of P. liebeana were similar to S. bergeri, there was expansion of Triassic specialized feeding types, including leaf mining. Permian–Triassic generalized herbivory remained relatively constant, but specialized herbivores more finely partitioned plant-host tissues via new feeding modes, especially in the Anisian. Insect-damaged leaf percentages for Dolomites Kungurian and Wuchiapingian floras were similar to those of lower Permian, north-central Texas, but only one-third that of southeastern Brazil. Global herbivore patterns for Early Triassic plant–insect interactions remain unknown.