Nutritive tissue rich in reserves in the cell wall and protoplast: the case of Manihot esculenta (Euphorbiaceae) galls induced by Iatrophobia brasiliensis (Diptera, Cecidomyiidae)

The galls can offer shelter, protection, and an adequate diet for the gall-inducing organisms. Herein, we evaluated the structure of Manihot esculenta leaves and galls induced by Iatrophobia brasiliensis in order to identify metabolic and cell wall composition changes. We expected to find a complex gall with high primary metabolism in a typical nutritive tissue. Non-galled leaves and galls were subjected to anatomical, histochemical, and immunocytochemical analyses to evaluate the structural features, primary and secondary metabolites, and glycoproteins, pectins, and hemicelluloses in the cell wall. The gall is cylindric, with a uniseriate epidermis, a larval chamber, and a parenchymatic cortex divided into outer and inner compartments. The outer compartment has large cells with intercellular spaces and stocks starch and is designated as storage tissue. Reducing sugars, proteins, phenolic compounds, and alkaloids were detected in the protoplast of inner tissue cells of galls, named nutritive tissue, which presents five layers of compact small cells. Cell walls with esterified homogalacturonans (HGs) occurred in some cells of the galls indicating the continuous biosynthesis of HGs. For both non-galled leaves and galls, galactans and xyloglucans were broadly labeled on the cell walls, indicating a cell growth capacity and cell wall stiffness, respectively. The cell wall of the nutritive tissue had wide labeling for glycoproteins, HGs, heteroxylans, and xyloglucans, which can be used as source for the diet of the galling insect. Manihot esculenta galls have compartments specialized in the protection and feeding of the galling insect, structured by nutritive tissue rich in resource compounds, in the cell walls and protoplast.

Hemiptera-induced galls of Sapium glandulosum have histological and cytological compartmentalization created with a large amount of carbohydrate

Gall formation impacts the development of plant species by altering the structure and mobilization of reserves, and the functional and physiological patterns of the host organ. The current study aimed to evaluate the impact generated by the Neolithus fasciatus galling insect (Hemiptera: Triozidae) in Sapium glandulosum leaves (Euphorbiaceae) at the cytological, histological, histochemical, and biochemical levels. Non-galled leaves and galls in the young, mature, and senescent stages were evaluated. The non-galled leaf has a uniseriate epidermis, stomata only on the abaxial side, a dorsiventral mesophyll, and parenchyma cells with thin primary walls containing chloroplasts with plastoglobules. The gall has a parenchymatous compartmentalized cortex. The young and mature galls already have a dense cytoplasm, especially in the inner cells of the cortex, with chloroplasts, mitochondria, Golgi complex, and large and evident nuclei. In senescent galls, there are signs of organelle degradation and cell digestion. Carbohydrates occur in greater amounts in the mature gall, mainly in the starch grain form, while proteins and lipids predominate in non-galled leaves. Secondary metabolites occur mainly in the young gall and may be related to its protection and to the signaling of its development. Sapium glandulosum galls have histological and cytological compartmentalization of the cortex with a large amount of carbohydrates, which supply energy to maintain the development of the structure.

Characterization of Bacillus velezensis 32a metabolites and their synergistic bioactivity against crown gall disease

Crown gall disease caused by Agrobacterium tumefaciens is considered to be the main bacterial threat of stone fruit plants in Mediterranean countries. In a previous study, Bacillus velezensis strain 32a was isolated from Tunisian rhizosphere soil and revealed high antagonistic potential against A. tumefaciens strains. In order to better characterize the antagonistic activity of this strain against this important plant pathogen, the production of secondary metabolites was analyzed using liquid chromatography coupled with mass spectrometry. The results revealed the production of different compounds identified as surfactins, fengycins, iturins and bacillibactin belonging to the lipopeptide group, three polyketides (macrolactins, oxydifficidin and bacillaenes), bacilysin and its chlorinated derivative; chlorotetaine. The involvement of lipopeptides in this antagonistic activity was ruled out by performing agar and broth dilution tests with pure molecules. Thus, the construction of B. velezensis 32a mutants defective in polyketides and bacilysin biosynthesis and their antagonistic activity was performed and compared to a set of derivative mutants of a comparable strain, B. velezensis GA1. The defective difficidin mutants (△dfnA and △dfnD) were unable to inhibit the growth of A. tumefaciens, indicating the high-level contribution of difficidin in the antagonism process. While the macrolactin deficient mutant (∆mlnA) slightly decreased the activity, suggesting a synergetic effect with difficidin. Remarkably, the mutant △dhbC only deficient in bacillibactin production showed significant reduction in its capacity to inhibit the growth of Agrobacterium.Taken collectively, our results showed the strong synergetic effect of difficidin and macrolactins and the significant implication of siderophore to manage crown gall disease.

Insect galls from the Botanical Garden of the Museu Nacional (Rio de Janeiro, RJ, Brazil)

The Botanical Garden of the Museu Nacional/Universidade Federal do Rio de Janeiro (Rio de Janeiro, RJ, Brazil) was investigated monthly from October, 2017 to December, 2019 in a total of 27 collections, each lasting four hours, following the methodology of random walking. Vegetative and reproductive organs of herbs, bushes and trees (up to 2 m high) were examined by two people. Voucher material was deposited in the Entomological Collection of the Museu Nacional (MNRJ)/Universidade Federal do Rio de Janeiro. We found 13 insect gall morphotypes in nine host plant species of four families. All host plants are native of Brazil, except Ficus microcarpa L.f. (Moraceae), which is naturalized. Myrtaceae and Moraceae were the plant families with the greatest richness of gall morphotypes. Eugenia L. (Myrtaceae) and Ficus L. (Moraceae) were the plant genera with the highest number of gall morphotypes. In several inventories in the Atlantic forest, Myrtaceae and Eugenia stand out for harboring a great variety of galls, while Moraceae and Ficus were never stood out for this reason. Most plant species mentioned in the present study were already known as hosts of gall-inducing insects in Brazil. However, for the first time, insect galls are reported on Ficus crocata (Miq.) Miq. (Moraceae). We found two new morphotypes on Eugenia florida DC. (Myrtaceae). Leaves, stems and buds were the galled organs. Cecidomyiidae were the most frequent inducers. Galls of Thysanoptera were also found. Inquilines were observed in leaf galls on Eugenia florida. They promoted differences in gall morphology and killed the gall-inducing larva.

Gall inducer Dasineura sp. alters the polyphenol profile and antioxidant activity of Peumus boldus stems

Peumus boldus, a tree native to Chile, is extensively used for medicinal purposes due to its richness in alkaloids and antioxidant polyphenols. A species of galling insect, Dasineura sp. induces structural and chemical changes on P. boldus stems while its galls are established and developed. Taking into account the antioxidant properties of P. boldus polyphenols, it would be expected that Dasineura sp. induces changes in the accumulation sites, chemical profile, and antioxidant activity of the P. boldus stem polyphenols, related to different reactive oxygen species (ROS) production levels during gall development. Dasineura sp. induces changes in the accumulation sites of total polyphenols, flavonols, and lignin, redirecting their accumulation toward the sites of greatest production of H2O2 and O2.-. Although changes in total polyphenol content would be expected, this did not vary significantly between non-galled and galled stems. However, the galling insect induced changes in the profile and concentration of soluble polyphenols, leading to the gall extracts' antioxidant capacity decreasing significantly during the maturation and senescence stages. Additionally, during the maturation stage, lignin deposition increases in the more peripheral gall tissues, which also contributes to ROS dissipation. The differences in the different gall developmental stages' antioxidant activity could be related to the identity and concentration of phenolic compounds in each gall extract, rather than to the total phenol content. Regardless of the mechanisms involved, the dissipation of the ROS generated by Dasineura sp. activity occurs, restoring the redox balance in galls and guaranteeing the success of the inducer.

Antivirulence effects of cell-free culture supernatant of endophytic bacteria against grapevine crown gall agent, Agrobacterium tumefaciens, and induction of defense responses in plantlets via intact bacterial cells

BACKGROUND

Crown gall disease caused by Agrobacterium tumefaciens is a very destructive affliction that affects grapevines. Endophytic bacteria have been discovered to control plant diseases via the use of several mechanisms. This research examined the potential for controlling crown gall by three endophytic bacteria that were previously isolated from healthy cultivated and wild grapevines including Pseudomonas kilonensis Ba35, Pseudomonas chlororaphis Ba47, and Serratia liquefaciens Ou55.

RESULT

At various degrees, three endophytic bacteria suppressed the populations of A. tumefaciens Gh1 and greatly decreased the symptoms of crown gall. Furthermore, biofilm production and motility behaviors of A. tumefaciens Gh1were greatly inhibited by the Cell-free Culture Supernatant (CFCS) of endophytic bacteria. According to our findings, CFCS may reduce the adhesion of A. tumefaciens Gh1 cells to grapevine cv. Rashe root tissues as well as their chemotaxis motility toward the extract of the roots. When compared to the untreated control, statistical analysis showed that CFCS significantly reduced the swimming, twitching, and swarming motility of A. tumefaciens Gh1. The findings demonstrated that the endophytic bacteria effectively stimulated the production of plant defensive enzymes including superoxide dismutase (SOD), polyphenol oxidase (PPO), peroxidase (POD), phenylalanine ammonia lyase (PAL), and total soluble phenols at different time intervals in grapevine inoculated with A. tumefaciens Gh1. The Ba47 strain markedly increased the expression levels of defense genes associated with plant resistance. The up-regulation of PR1, PR2, VvACO1, and GAD1 genes in grapevine leaves indicates the activation of SA and JA pathways, which play a role in enhancing resistance to pathogen invasion. The results showed that treating grapevine with Ba47 increased antioxidant defense activities and defense-related gene expression, which reduced oxidative damage caused by A. tumefaciens and decreased the incidence of crown gall disease.

CONCLUSION

This is the first study on how A. tumefaciens, the grapevine crown gall agent, is affected by CFCS generated by endophytic bacteria in terms of growth and virulence features. To create safer plant disease management techniques, knowledge of the biocontrol processes mediated by CFCS during microbial interactions is crucial.

Insect galls of Atlantic Forest areas of Serra da Bodoquena (MS, Midwestern Brazil)

An inventory of insect galls of Serra da Bodoquena (MS, Midwestern Brazil) was carried out in an area of semideciduous seasonal forest situated in the Califórnia Farm. Three field works were done in August/2011, December/2011 and April/2012, when the local vegetation was examined during 40 hours per expedition. Fifty-eight gall morphotypes were found on 40 host plants, 38 of them native. The host plants are distributed in 18 families. The native plants include eight endemic species in Brazil, which together totaled 14 gall morphotypes. Zanthoxylum L. sp. (Rutaceae), an endemic genus in Brazil, hosts one gall morphotype. The non endemic native plants totaled 26 gall morphotypes. Ten new host plants are recorded for the first time in Brazil. The medium number of gall morphotypes per plant species was 1.45. Salicaceae, Bignoniaceae, and Asteraceae presented the highest number of galled species and the greatest gall richness. Leaves were the most frequent galled plant organ and there was a predominance of globoid galls. Diptera (Cecidomyiidae) were the most frequent gallers, but Hemipteran and Thysanopteran galls were also found. The associated fauna was composed of inquilines (Diptera: Muscomorpha and Cecidomyiidae - Trotteria sp., and Thysanoptera), successors (Psocoptera), and parasitoids (Hymenoptera).

Insect galls from Amazon rainforest areas in Rondônia (Brazil)

This study aimed at survey insect galls of an Amazon rainforest area in Rondônia, Brazil. We found 152 gall morphotypes in 103 plant species. Fabaceae were the host with the greatest gall richness. Leaves were the most galled organ. Globose and glabrous galls were the most frequent. Cecidomyiidae were responsible for most of the galls. This is the first record of 110 galls morphotypes and 23 host plants species in this biome. Ten gallers are endemic in Brazil. Five genera of Cecidomyiidae were first recorded in Rondônia as well as Schismatodiplosis lantanae Rübsaamen, 1908.

The formation of a rolling larval chamber as the unique structural gall of a new species of cynipid gall wasps

Insect galls, which often have complex external and internal structures, are believed to have adaptive significance for the survival of insects inside galls. A unique internal structure was discovered in the gall of a new cynipid species, Belizinella volutum Ide & Koyama, sp. nov., where the larval chamber could roll freely in the internal air space of the gall. Observations of the live galls using micro-computed tomography (micro-CT) revealed its formation process. The larval chamber becomes isolated from the internal parenchyma soon after the gall reaches the maximum diameter and is able to roll as the internal air space is expanding from the surrounding parenchyma to the outer gall wall. The enemy hypothesis could partly explain the adaptive significance of the unique structure of the gall of B. volutum.

A transcriptional activator effector of Ustilago maydis regulates hyperplasia in maize during pathogen-induced tumor formation

Ustilago maydis causes common smut in maize, which is characterized by tumor formation in aerial parts of maize. Tumors result from the de novo cell division of highly developed bundle sheath and subsequent cell enlargement. However, the molecular mechanisms underlying tumorigenesis are still largely unknown. Here, we characterize the U. maydis effector Sts2 (Small tumor on seedlings 2), which promotes the division of hyperplasia tumor cells. Upon infection, Sts2 is translocated into the maize cell nucleus, where it acts as a transcriptional activator, and the transactivation activity is crucial for its virulence function. Sts2 interacts with ZmNECAP1, a yet undescribed plant transcriptional activator, and it activates the expression of several leaf developmental regulators to potentiate tumor formation. On the contrary, fusion of a suppressive SRDX-motif to Sts2 causes dominant negative inhibition of tumor formation, underpinning the central role of Sts2 for tumorigenesis. Our results not only disclose the virulence mechanism of a tumorigenic effector, but also reveal the essential role of leaf developmental regulators in pathogen-induced tumor formation.

Vascular implications of Dasineura sp. galls' establishment on Peumus boldus stems

Some chewing larvae are capable of inducing galls in the host vascular cylinder, e.g. Dasineura sp. (Cecidomyiidae) on Peumus boldus stems. Due to the medicinal and economic importance of P. boldus, the anatomical and functional implications of establishment of Dasineura sp. on P. boldus stems were investigated. We asked if establishment of Dasineura sp. in P. boldus stems induces abnormalities at the cellular and organizational level of the vascular system that increase during gall development in favour of the hydric status of the gall. Anatomical alterations induced in the stems during gall development were determined. Cytohistometric analyses in mature galls were compared to non-galled stems, and water potential and leaf area of non-galled stems were compared with galled stems. Dasineura sp. establishes in the vascular cambium, leading to delignification and rupture of xylem cells, inhibiting formation of phloem and perivascular sclerenchyma. Gall diameter increases together with larval feeding activity, producing a large larval chamber and numerous layers of nutritive tissue, vascular parenchyma, and sclerenchyma. These anatomical alterations do not affect the leaf area of galled stems but favour increased water flow towards these stems. The anatomical alterations induced by Dasineura sp. in P. boldus stems guarantee water and nutrient supply to the gall and larva. After the inducer exits stems, some host branches no longer have vascular connections with the plant body.

Biology and morphometric relationship of gall inducers Contarinia sp. and corresponding parasitoids for swollen galls of Nitraria sibirica pall

Galls function as provide shelter for gall inducers, guarding them against their natural enemies. Previous research has illuminated the interactions between galls, gall inducers, and their corresponding parasitoids within various caltrop plants. However, less is known about these relationships within Nitraria sibirica, particularly regarding the efficacy of parasitism. Therefore, this study aimed to identify the morphometric relationships among the swollen galls, gall inducers, and their parasitoids. Two species of gall inducers and three species of parasitoids were obtained from the swollen galls of N. sibirica. The correlations of the parasitization indexes, the lifespan of gall inhabitants, and temperature and the morphometric relationships between the galls and their inhabitants were analyzed. The dominant gall inducer identified was Contarinia sp. (Diptera: Cecidomyiidae). Furthermore, it was observed that three solitary parasitoids attacked Contarinia sp. in the swollen galls, with only Eupelmus gelechiphagus acting as an idiobiont ectoparasitoid. The dominant parasitoids were Platygaster sp. and Cheiloneurus elegans at sites 1 and 2, respectively, with Platygaster sp. displaying greater abundance than C. elegans in the swollen galls. The lifespan of the gall inhabitants shortened gradually as the temperature increased. Moreover, the optimal number of gall chambers ranged from two to four per swollen gall with maximized fitness, which can be considered the optimal population density for the gall inducer Contarinia sp. Morphometric analysis exhibited a strong linear correlation between gall size and chamber number or the number of gall inhabitants, as well as a weak correlation between gall size and body size of the primary inhabitants of swollen galls. Our results highlight the importance of the biological investigation of parasitoids and gall inducers living in closed galls with multiple chambers and may pave the way for potential application in biological control.

Structural patterns of Lepidoptera galls and the case of Andescecidium parrai (Cecidosidae) galls on Schinus polygama (Anacardiaceae)

Gall anatomical and metabolic peculiarities are determined by the feeding habit of the gall inducer, but develop under the constraints of the host plants. The chewing habit of the Lepidoptera larvae imposes a high impact on the host plant cells, and supposedly drives peculiar structural and histochemical patterns. So, our starting point was the search of such patterns in literature, and the test of these traits on the Andescecidium parrai (Cecidosidae)-Schinus polygama (Anacardiaceae) system, as a case study in Chilean flora. The literature on the structure of lepidopteran galls in the temperate and tropical regions comprises 13 works, describing stems as the most frequent host organs, followed by leaves, buds, and flowers. As common structural traits of Lepidoptera galls, the literature converge in describing the processes of cell hypertrophy and hyperplasia, resulting in a variable number of common storage parenchyma layers, interspersed by the redifferentiated sclerenchyma, vascular, and typical nutritive cells around the larval chamber. These nutritive cells accumulate lipids and proteins, which support the lepidopteran larvae nutrition. As expected, the A. parrai galls follow the patterns herein described for the lepidoptera-induced galls, but with peculiarities associated with its host organ. Even though the Lepidoptera galls have destructive mouthparts and can induce large and complex galls, they cannot alter important conservative features of their hosts' organs.

Cecidomyiidae (Diptera) on Myrtaceae in Brazil: richness and geographic distribution

Myrtaceae have a wide geographical distribution in Brazil and host a great richness of Cecidomyiidae galls. However, the number of cecidomyiid species on them has not yet been established and the knowledge of their geographic distribution is deficient. We provide the first list of cecidomyiid species on Myrtaceae and analyze their distribution in Brazilian biomes. A literature review was performed and new data were obtained from herbarium specimens of the Jardim Botânico do Rio de Janeiro. In Brazil, 13 species of Myrtaceae of five genera shelter described species of gall midges. Eugenia hosts the greatest richness of gall-inducers. All plant species have human uses and are native to Brazil, being seven endemic. Myrtaceae shelter 25 cecidomyiid species of 13 genera in 25 gall morphotypes. Sixteen species occur on endemic hosts, highlighting the peculiarity of the Brazilian fauna. These Cecidomyiidae occur collectively in five biomes, but most species (92%) are known from the Atlantic Forest, where 72% appear exclusively. Sixty per cent are restricted to a single Brazilian state, indicating their still poorly known distribution.

A new perspective on plant defense against foliar gall-forming aphids through activation of the fruit abscission pathway

The peach aphid Tuberocephalus momonis seriously damages leaves and forms galls in the peach species Prunus persica f. rubro-plena, P. persica, and P. davidiana. Leaves bearing galls formed by these aphids will be abscised at least two months earlier than the healthy leaves on the same tree. Thus, we hypothesize that gall development is likely to be governed by phytohormones involved in normal organogenesis. The soluble sugar content was positively correlated between gall tissues and fruits, suggesting that the galls are sink organs. The results of UPLC-MS/MS analysis showed that higher concentrations of 6-benzylaminopurine (BAP) accumulated in both the gall-forming aphids, the galls themselves and the fruits of peach species than in healthy leaves, suggesting that BAP was being synthesized by the insects to stimulate the establishment of a gall. A significant increase in the concentrations of abscisic acid (ABA) in fruits and jasmonic acid (JA) in gall tissues indicated that these plants are defending from the galls. The concentrations of 1-amino-cyclopropane-1-carboxylic acid (ACC) significantly increased in gall tissues compared with healthy leaves, and were positively correlated with both fruit and gall development. In addition, transcriptome sequencing analysis revealed that during gall abscission, differentially expressed genes in both 'ETR-SIMKK-ERE1' and 'ABA-PYR/PYL/RCAR-PP2C-SnRK2' were significantly enriched during gall abscission. Our results showed that ethylene pathway was involved in the abscission of gall, and this gall abscission allowed the host plants to protect themselves from the gall-forming insects, at least partially.

Gall-inducing Eriophyes tiliae stimulates the metabolism of Tilia platyphyllos leaves towards oxidative protection

Red galls have high levels of anthocyanins which perform different physiological functions, such as antioxidants and protection against UVB radiation. High levels of anthocyanins and other polyphenols have been associated with low photosynthetic pigment content. In environments with high levels of UVB radiation, it would thus be expected that red galls would have high anthocyanin and polyphenol levels and low photosynthetic pigment contents, enabling the gall with high antioxidant capacity compared to its host organ. The red galls induced by Eriophyes tiliae, and their host environment of Tilia platyphyllos leaves in the Mediterranean climate of Chile, were investigated in relation to their anatomy, histochemistry, pigment, sugar, protein, and polyphenol contents, and antioxidant capacity. The anthocyanin, sugars, and polyphenol contents and the antioxidant capacity were increased in galls. Photosynthetic pigment and protein contents were higher in non-galled leaves. The high levels of anthocyanin and total polyphenols increase the galls' antioxidant capacity in the high UV radiation environment of a Mediterranean climate. The establishment of E. tiliae induced redifferentiation of nutritive tissue, rich in sugars, proteins, and lipids, and an inner epidermis with trichomes and long emergences. E. tiliae galls' structural and metabolic features are probably enhanced towards mite nutrition and protection. The current results shed light on the role of anthocyanin in the antioxidant protection of plant galls in environments with high UV irradiance.

A broad spectrum of host plant responses to the actions of the gall midge: case study of Robinia pseudoacacia L. and Obolodiplosis robiniae (Haldeman)

This study aims to provide insights into plant-insect interaction during the formation and development of open gall structure on the leaves of Robinia pseudoacacia during gall formation by Obolodiplosis robiniae. This was the first time such far-reaching studies were performed at a biochemical and anatomical level. The gall wall is created from a few thick cells covered with epidermis. This parenchymatous nutritive tissue is rich in starch. Sclerenchyma only occurs around the vascular bundles as a result of the lignification of the parenchyma of the bundle sheaths. The level of reactive oxygen species (ROS) in the new structure was reduced and catalase activity was inhibited, which suggests another pathway of ROS decomposition - e.g. by ascorbate or glutathione peroxidase. The gall structure was combined with an increasing level of protein and non-protein thiols. Phenols seems to be a good protective factor; whose level was lower in infected leaflets. Levels of MUFA (monosaturated fatty acids) and SFA (saturated fatty acids) rose, probably as source of food for insects. The amount of fatty acid is positively correlated with the plant response. We detected that non infected leaflets produced C6:0 (hexanoic acid) and C8:0 (octanoic acid) fatty acids connected with odor. Changes in gall color as they develop are connected with photosynthetic pigments degradation (mainly chlorophylls) where the pathway of astaxanthin transformation to fatty acid is considered to be the most important process during gall maturation. Nutritive tissue is composed mainly of octadecanoic acid (C18:0) - a main source of food for O. robiniae.

Host plant intraspecific variation determines gall traits

Galls display a multiplicity of traits, including colours, which are driven by pigment accumulation. Their conspicuousness has attracted researchers' attention and several hypotheses have been raised. However, plants themselves vary intra-specifically, including in their pigment concentrations. As galls are a result of host tissue development, colours may be a by-product of the host's own traits, being more conspicuous simply because the sites where galls develop already have the predisposition to accumulate more pigment. Here, we call this the host variation hypothesis. We test this hypothesis using the system of galls induced by Palaeomystella oligophaga on Macairea radula host plant. Using spectrophotometry, we calculated the Anthocyanin Reflectance Index (ARI) of gall projections, which are responsible for their characteristic colours. We tested the influence of occupant identity (galling insect or any natural enemy), gall volume, parenchyma thickness, height from the ground, ARI of leaf, ARI of gall surface and ARI of the respective stem. We corroborated the host variation hypothesis since the anthocyanin content in stems and in galls' projections were positively related. Moreover, anthocyanin in galls' projections was positively related to anthocyanin in the gall surface and negatively related to gall volume and parenchyma thickness. This shows that, besides the host specificities, galls' own traits may also be responsible for pigment accumulation, influencing their colours. In this study, using colour as an example, we show that although galls tend to be considered complex expressions of galling insects' stimuli, their traits may be simply influenced by previous and specific attributes of the host organs.

Plant Gall Diversity in Burned Semi-natural Grasslands in Japan

We surveyed woody plants, including oaks and chestnuts (Quercus L. and Castanea Mill.), and recorded the inhabiting galls induced by oak gall wasps (Hymenoptera: Cynipidae: Cynipini) at seven Japanese semi-natural grassland sites maintained by traditional regular burning with two of the seven abandoned grassland areas. Woody plants were established in all burned and abandoned grasslands. Oak species were found at four of the seven sites. In total, 15 types of cynipid galls were recorded at all four sites where oak species were found. However, the occurrence of species was site-specific for host trees and cynipid galls. Although a few ecological studies of oak gall wasps inhabiting grassland environments, which have rapidly decreased in recent decades, have been conducted, this study suggests that semi-natural grasslands may be potential habitats for oak gall wasps and their host trees, and we provide a checklist of oak gall wasps with host oak records in semi-natural grasslands throughout Japan.

Mechanisms of hydraulic conductivity in the leaf galls of Meunieriella sp. (Cecidomyiidae) in Avicennia schaueriana (Acanthaceae): does vascularization explain the preferred sites of induction?

Intralaminar galls of Meunieriella result from ground tissue proliferation in leaves of Avicennia schaueriana, a typical halophytic mangrove. We tested if the preferred sites of gall induction were the midribs and secondary veins (SV) at the basal leaf portion, where the galls were expected to be largest; and if the vascular system in galls and adjacent regions was altered to favour water supply in galls, thus increasing their growth. Gall induction sites and gall sizes were quantified according to leaf portions and regions. Anatomical and histometric analyses in vascular and ground tissues of galls and adjacent regions were compared to equivalent regions of non-galled leaves. The galls were largest at basal sites on leaves, the midrib and SV. More galls occurred on the apical portion of the leaf, and on the leaf blade and secondary vein regions. Changes in shape and vascular system area, number and diameter of vessel elements were detected in both galls and adjacent regions. Fewer and smaller-sized vessel elements were observed in regions proximal to the galls and inside them. Gall size is not related with preferred induction sites, which could be explained by factors such as thermal balance. Alterations in the vascular system indicate reduced hydraulic conductivity in the xylem in the proximal region and inside galls, leading to water leakage to gall parenchyma cells. This compensatory mechanism explains the expansion and proliferation of water storage and spongy parenchyma cells in the galls, explaining the higher growth in more vascularized regions.

Parasitoid impairment on the galling Lopesia sp. activity reflects on the cytological and histochemical profiles of the globoid bivalve-shaped gall on Mimosa gemmulata

Gall cytological and histochemical features established by the constant feeding activity of the associated gall inducer may be changed due to the attack of parasitoids. We accessed two tri-trophic systems involving the globoid bivalve-shaped gall on Mimosa gemmulata Barneby (Fabaceae) and its galling undescribed species of Lopesia (Diptera: Cecidomyiidae), which may be ectoparasitized by Torymus sp. (Hymenoptera: Torymidae) or endoparasitized by a polyembryonic Platygastridae (Hymenoptera), as models of study. The ectoparasitoid species paralyzes and kills Lopesia sp. larva, which stops the feeding stimuli, while the endoparasitoid larvae feed in Lopesia sp. larva body and keep it alive for a certain time. Our hypothesis is that the time lapse of Lopesia sp. feeding impairment by the two parasitoids will cause distinct cytological and histochemical responses in the ecto- and endoparasitized galls compared to the non-parasitized condition. In both parasitoidism cases, the impairment of the feeding activity of the galling Lopesia sp. directs the common storage and nutritive cells toward a similar process of induced cell death, involving cell collapse and loss of membrane integrity. The cell metabolism is maintained mainly by mitochondria, and by the translocation of lipids from the common storage tissue, via plasmodesmata, through the living sclereids of the mechanical zone toward the nutritive tissue. Accordingly, the parasitoid impairment on the feeding activity of Lopesia sp. larvae causes precocious senescence, but similar cytological alterations, and no impact over the histochemical profiles, regarding lipids, reactive oxygen species, and secondary metabolites, which support gall metabolism along the parasitoid cycles.

Anatomical profiles validate gall morphospecies under similar morphotypes

Plant galls are generated by the stimuli of gall-inducing organisms on their hosts, creating gall morphotypes that vary in color, shape, size, and tissue organization. Herein, we propose to compare the structural features of gall morphotypes on the superhost Croton floribundus (Euphorbiaceae) in order to recognize gall morphospecies, i.e., galls with similar shapes but different internal structures. Non-galled leaves and galls were analyzed macroscopically, histologically, and histochemically for the detection of primary metabolites, and the results obtained were used for statistical analyses of similarity. Among the eight gall morphospecies, four are globoid, two are lenticular, one is fusiform and one is marginal leaf rolling. Stomatal differentiation and the occurrence of different types of trichomes were impaired in some gall morphospecies. Three patterns of organization of the ground system are recognized, ranging from the maintenance of mesophyll cells that differentiate into palisade and spongy cells dorsiventrally to the formation of a complex cortex with three morphofunctional layers. The marginal leaf rolling galls have the simplest anatomical structures, quite similar to those of the non-galled host leaf, while lenticular, globoid (types I to IV), and fusiform galls are anatomically more complex. Herein, we report on eight gall morphospecies occurring on C. floribundus, which are distinguished by morpho-anatomical attributes and show the disruption of the morphogenetic patterns of the host leaf toward the morphogenesis of unique gall features.

Genomic analysis provides novel insights into diversification and taxonomy of Allorhizobium vitis (i.e. Agrobacterium vitis)

BACKGROUND

Allorhizobium vitis (formerly named Agrobacterium vitis or Agrobacterium biovar 3) is the primary causative agent of crown gall disease of grapevine worldwide. We obtained and analyzed whole-genome sequences of diverse All. vitis strains to get insights into their diversification and taxonomy.

RESULTS

Pairwise genome comparisons and phylogenomic analysis of various All. vitis strains clearly indicated that All. vitis is not a single species, but represents a species complex composed of several genomic species. Thus, we emended the description of All. vitis, which now refers to a restricted group of strains within the All. vitis species complex (i.e. All. vitis sensu stricto) and proposed a description of a novel species, All. ampelinum sp. nov. The type strain of All. vitis sensu stricto remains the current type strain of All. vitis, K309T. The type strain of All. ampelinum sp. nov. is S4T. We also identified sets of gene clusters specific to the All. vitis species complex, All. vitis sensu stricto and All. ampelinum, respectively, for which we predicted the biological function and infer the role in ecological diversification of these clades, including some we could experimentally validate. All. vitis species complex-specific genes confer tolerance to different stresses, including exposure to aromatic compounds. Similarly, All. vitis sensu stricto-specific genes confer the ability to degrade 4-hydroxyphenylacetate and a putative compound related to gentisic acid. All. ampelinum-specific genes have putative functions related to polyamine metabolism and nickel assimilation. Congruently with the genome-based classification, All. vitis sensu stricto and All. ampelinum were clearly delineated by MALDI-TOF MS analysis. Moreover, our genome-based analysis indicated that Allorhizobium is clearly separated from other genera of the family Rhizobiaceae.

CONCLUSIONS

Comparative genomics and phylogenomic analysis provided novel insights into the diversification and taxonomy of Allorhizobium vitis species complex, supporting our redefinition of All. vitis sensu stricto and description of All. ampelinum. Our pan-genome analyses suggest that these species have differentiated ecologies, each relying on specialized nutrient consumption or toxic compound degradation to adapt to their respective niche.

Cell death and changes in primary metabolism: the onset of defence in Eucalyptus in the war against Leptocybe invasa

BACKGROUND

Here, we investigated changes in primary metabolism and cell death around oviposition sites in two hybrid clones of Eucalyptus with different degrees of resistance to Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae), as well as tolerance to water deficiency.

RESULTS

We showed that apices of the resistant clone with oviposition had a higher content of amino acids, organic acids and the compound putrescine compared with those of the susceptible clone with oviposition. By contrast, apices of the resistant clone with oviposition had lower sugar and pyruvate organic acid content than those of the susceptible clone with oviposition. Small areas of necrosis were induced around the oviposition sites in the stem apices of Eucalyptus 24 h after infestation. The resistant clone developed larger necrotic areas that showed progressive increases 24-72 h after infestation compared with the susceptible clone, in which cell death was significantly lower and no changes were observed in necrotic area over time. Thus, the programmed death of cells around the egg, modulated by several amino acids, is likely the first defence response of Eucalyptus against L. invasa.

CONCLUSION

Our results serve as the basis for the early identification of key metabolites produced in plants in defence against galling insects. © 2022 Society of Chemical Industry.

Vascular traits of stem galls: Cell increment versus morphogenetic constraints in wood anatomy

Eremanthus erythropappus hosts globoid stem galls induced by Neolasioptera sp. (Diptera: Cecidomyiidae) close to the stem apex, which do not compromise the shoot apical meristem (SAM). We hypothesize that maintenance of the SAM, as well as the increasing number of leaves per branch and of galled stem lengths and diameters, are a consequence of alterations in vascular cells and, consequently, in the priority for water flow from non-galled stems to the stem galls. Our study focuses on the globoid stem galls to evaluate if gall induction and development promote changes in structure and function of secondary xylem cells. Anatomical, cytological, histometric and physiological methods were used to analyse non-galled stem branches (NGS), mature globoid stem galls and stem portions below and above the galls. These analyses revealed that vessel elements are larger in stem galls and in stem portions above the galls. Under Neolasioptera sp. induction activity, the vascular cambium of E. erythropappus produces less numerous but larger vessel elements and overproduces parenchyma cells. Contrary to the vascular constriction hypothesis proposed for bacterial galls, the vascular traits of the Neolasioptera sp. stem galls on E. erythropappus result in priority for water flow to galls and the non-galled portions above the galls, allowing the maintenance of galled stem growth and development.

Transcriptional up-regulation of host-specific terpene metabolism in aphid-induced galls of Pistacia palaestina

Galling insects gain food and shelter by inducing specialized anatomical structures in their plant hosts. Such galls often accumulate plant defensive metabolites protecting the inhabiting insects from predation. We previously found that, despite a marked natural chemopolymorphism in natural populations of Pistacia palaestina, the monoterpene content in Baizongia pistaciae-induced galls is substantially higher than in leaves of their hosts. Here we show a general up-regulation of key structural genes in both the plastidial and cytosolic terpene biosynthetic pathways in galls as compared with non-colonized leaves. Novel prenyltransferases and terpene synthases were functionally expressed in Escherichia coli to reveal their biochemical function. Individual Pistacia trees exhibiting chemopolymorphism in terpene compositions displayed differential up-regulation of selected terpene synthase genes, and the metabolites generated by their gene products in vitro corresponded to the monoterpenes accumulated by each tree. Our results delineate molecular mechanisms responsible for the formation of enhanced monoterpene in galls and the observed intraspecific monoterpene chemodiversity displayed in P. palaestina. We demonstrate that gall-inhabiting aphids transcriptionally reprogram their host terpene pathways by up-regulating tree-specific genes, boosting the accumulation of plant defensive compounds for the protection of colonizing insects.

Vibrational Study (Raman, SERS, and IR) of Plant Gallnut Polyphenols Related to the Fabrication of Iron Gall Inks

FT-Raman, FTIR, and SERS spectra of the structurally related gallnut polyphenols tannic acid, gallic acid, pyrogallol, and syringic acid are reported in this work aiming at performing a comparative assignation of the bands and finding specific marker features that can identify these compounds in complex polyphenol mixtures. Tannic and gallic acids are the principal components in oak gallnuts, and they can be found in iron gall inks. The different functional groups existing in these molecules and their spatial distribution lead to slight changes of the vibrations. The Raman spectra are dominated by bands corresponding to the ring vibrations, but the substituents in the ring strongly affect these vibrations. In contrast, the FTIR spectra of these molecules are dominated by the peripheral oxygen-containing substituents of the aromatic ring and afford complementary information. SERS spectroscopy can be used to analyze trace amounts of these compounds, but the spectra of these polyphenols show strong changes in comparison with the Raman spectra, indicating a strong interaction with the metal. The most significant modification observed in the SERS spectra of these compounds is the weakening of the benzene 8a ring vibration and the subsequent intensification of the 19a mode of the benzene ring. This mode is also more intense in the FTIR spectra, and its intensification in the SERS spectra could be related to a drastic change in the molecular polarizability associated with the interaction of the polyphenol with the metal in Ag NPs.

Distinct cytological mechanisms for food availability in three Inga ingoides (Fabaceae)-Cecidomyiidae gall systems

Gall cytological, metabolic, and structural traits are established due to the feeding habits of the associated galling herbivores, and sometimes are influenced by other organisms involved in the interaction. We tested this assumption on three gall morphotypes, the globoid, the lenticular, and the fusiform, induced by Cecidomyiidae on leaflets of Inga ingoides (Rich.) Willd. (Fabaceae: Caesalpinioideae). Taking for granted that the three Cecidomyiidae galls are induced on the same host plant and organ, we assume that the cytological and histochemical traits of their nutritive cells may be similar, but under the fungi influence, the ambrosia gall cytological profile may be peculiar and reflect on the accumulation of primary metabolites. The ambrosia globoid galls involve three organisms (host plant, gall inducer, and fungi), while the fusiform and the lenticular galls involve two organisms (host plant and gall inducer). The accumulation of primary metabolites is similar among the three gall morphotypes, except for the non-detection of reducing sugars in the fusiform galls. The fungi presence can impact the system but does not define exclusive features for the ambrosia globoid galls when compared to the lenticular and fusiform morphotypes. In fact, the cytological traits have revealed three different cytological mechanisms for food resources availability to the three galling Cecidomyiidae: (a) cell wall destructuring and cell death by fungi intermediation in the ambrosia globoid galls, (b) necrosis-type cell death in the fusiform galls, and (c) maintenance of continuous metabolic activity in the lenticular galls.

Opine biosynthesis in naturally transgenic plants: Genes and products

The plant pathogen Agrobacterium transfers DNA into plant cells by a specific transfer mechanism. Expression of this transferred DNA or T-DNA leads to crown gall tumors or abnormal, hairy roots and the synthesis of specific compounds, called opines. Opines are produced from common plant metabolites like sugars, amino acids and α-keto acids, which are combined into different low molecular weight structures by T-DNA-encoded opine synthase enzymes. Opines can be converted back by Agrobacterium into the original metabolites and used for agrobacterial growth. Recently it has been discovered that about 7% of Angiosperms carry T-DNA-like sequences. These result from ancient Agrobacterium transformation events, followed by spontaneous regeneration of transformed cells into natural genetically transformed organisms (nGMOs). Nearly all nGMOs identified up to date carry opine synthesis genes, several of these are intact and potentially encode opine synthesis. So far, only tobacco and cuscuta have been demonstrated to contain opines. Whereas opines from crown gall and hairy root tissues have been studied for over 60 years, those from the nGMOs remain to be explored.

A small Ustilago maydis effector acts as a novel adhesin for hyphal aggregation in plant tumors

The biotrophic basidiomycete fungus Ustilago maydis causes smut disease in maize. Hallmarks of the disease are characteristic large tumors in which dark pigmented spores are formed. Here, we functionally characterized a novel core effector lep1 (late effector protein 1) which is highly expressed during tumor formation and contributes to virulence. We characterize lep1 mutants, localize the protein, determine phenotypic consequences upon deletion as well as constitutive expression, and analyze relationships with the repellent protein Rep1 and hydrophobins. In tumors, lep1 mutants show attenuated hyphal aggregation, fail to undergo massive late proliferation and produce only a few spores. Upon constitutive expression, cell aggregation is induced and the surface of filamentous colonies displays enhanced hydrophobicity. Lep1 is bound to the cell wall of biotrophic hyphae and associates with Rep1 when constitutively expressed in hyphae. We conclude that Lep1 acts as a novel kind of cell adhesin which functions together with other surface-active proteins to allow proliferation of diploid hyphae as well as for induction of the morphological changes associated with spore formation.

Physiological response of Populus nigra 'Italica' to galling aphids feeding

Although gall-inducing aphids, namely Pemphigus bursarius (L.) and P. phenax Börner et Blunck, are widely known as serious pests for their secondary hosts (lettuce and carrot, respectively), the physiological mechanism of their gall induction on Populus L. trees still requires a better understanding. In this study, we compared physiological parameters, i.e. H₂ O₂ , electrolyte leakage (E_L ), MDA, APX and GPOD. Changes in physiological parameters were analysed in foliar tissues with galls and in the gall tissues themselves and compared to leaves without galls. Significantly higher H₂ O₂ levels were observed in P. phenax galls when compared to leaves with galls. In turn, the highest E_L of cells and MDA content was in P. bursarius galls. Other samples had lower or similar oxidative stress marker levels to leaves without galls. APX and GPOD had similar activity profiles in galls of both aphid species. Their activity decreased significantly in gall tissues, where it was even ten-fold lower than in leaves without galls. Data generated in this study indicate that patterns of the physiological features, e.g. ROS accumulation and cell membrane integrity, of Populus leaves with galls and galls alone depends on the gall-inducing aphid species. Where decreased APX and GPOD activity, especially in gall tissues, indicated a reduction in the antioxidant potential of these neoformed structures.

Differences in native and introduced chalcid parasitoid communities recruited by the invasive chestnut pest Dryocosmus kuriphilus in two Iberian territories

Dryocosmus kuriphilus (Hymenoptera: Cynipidae) is a global invasive gall wasp and a pest of chestnuts (Castanea spp.). A study of the Chalcidoidea parasitoid community of D. kuriphilus was undertaken over two years, from March 2017 to March 2019, at 15 sites in south and northwest Spain (Málaga and Galicia regions). More than 18,000 galls were collected, and 1153 parasitoids belonging to 22 species of seven chalcidoid families, plus two individuals of an inquiline Cynipidae, Synergus facialis, emerged. Richness was higher in the Málaga region, with 20 species, while 17 parasitoids and one inquiline were identified in Galicia. The parasitism rate of native chalcid parasitoid species in both regions was low. Eupelmus urozonus and Mesopolobus lichtensteini were the most abundant native species. Mesopolobus tibialis was a dominant species in south Spain, while Ormyrus pomaceus was a dominant species in northwest Spain. Our results revealed the existence of a sub-community of univoltine, probably host specialized, parasitoids in south Spain, which overwinter in galls, exhibiting a similar life cycle to Torymus sinensis. These species were Torymus notatus, Aulogymnus bicolor, Aulogymnus obscuripes and Aulogymnus balani. Data on the recovery of T. sinensis after release in the south Spain region show it to be well established, but its numbers are still low in northwest Spain.

Cecidology: Anatomy of a biohack

Galls are abnormal plant growths induced by animals, especially insects, to foster their own developing offspring. Which molecular malware gall-inducers use to hack into the plant's genetic programs is unclear. In an aphid, a gene affecting gall color has been discovered, part of a large family of putative effectors.

Differential development times of galls induced by Leptocybe invasa (Hymenoptera: Eulophidae) reveal differences in susceptibility between two Eucalyptus clones

BACKGROUND

The significance of morphological responses of hosts on susceptibility against gall-inducing insects is relatively unknown, especially in planted forests. Here, we investigate the temporal morphological responses (gall development) induced by the invasive gall wasp Leptocybe invasa and the subsequent insect development in two Eucalyptus clones.

RESULTS

Our results identified a novel stage of gall development, not previously reported, termed here 'brownish ring'. In both hosts similar gall development stages were observed. Although L. invasa oviposited in both clones, comparison of external morphological traits of galls over time revealed a differential response in the number of galls between clones. Comparison of the developmental time of each gall and insect stage between clones suggests that plant defense mechanisms against L. invasa are activated shortly after oviposition by the wasp, yet before gall formation.

CONCLUSION

Gall number is an important parameter that should be used to measure host susceptibility among Eucalyptus clones. To the best of our knowledge, this is the first study showing differential morphological responses induced by a galling insect, even before gall formation, revealing differences in susceptibility between different plant hosts. These findings provide insight into the use of early stages of gall formation by L. invasa to prevent invasion and establishment of this pest.

Hemicelluloses and associated compounds determine gall functional traits

The intriguing questions concerning gall development refer to the processes of the remodelling of the host plant organ. Such processes involve the restructuring of cell walls and can be influenced by phenolics, indole-3-acetic acid (IAA) and reactive oxygen species (ROS). Alterations in cell walls demand the interference in the coupling of cellulose fibrils and hemicelluloses (xyloglucans) at specific stages of gall development. In addition to cell wall remodelling, hemicelluloses, such as the, xyloglucans and heteromannans can act as reserve carbohydrates, while xylans provide rigidity to the secondary cell walls. Developmental traits of the lenticular, fusiform and globoid galls on Inga ingoides (Fabaceae) were analysed using anatomical, cytometric, histochemical and immunocytochemical tools. Phenolics, IAA and ROS accumulated in similar gall tissue compartments, and may have influenced the restructuring of hemicelluloses and pectins. Contrary to expectations, cell wall flexibility regarding the dynamics of xyloglucans and cellulose fibrils does not relate to a temporal scale. The detection of xyloglucans in nutritive cell walls relate to carbohydrate nutritional resources to the galling insect, while xylans were associated to the lignified cell walls. Heteromanans were not detected, either in non-galled or galled tissues. The patterns of cell expansion during gall development relied on the relationship among phenolics, ROS and IAA with the hemicelluloses (xyloglucans and xylans) and cellulose fibrils. Although cell wall dynamics is specific to each gall morphotype in I. ingoides, the xyloglucans function as carbohydrate reserve to the gall inducers, which constitutes a functional trait common to the three morphotypes.

Plants make galls to accommodate foreigners: some are friends, most are foes

At the colonization site of a foreign entity, plant cells alter their trajectory of growth and development. The resulting structure - a plant gall - accommodates various needs of the foreigner, which are phylogenetically diverse: viruses, bacteria, protozoa, oomycetes, true fungi, parasitic plants, and many types of animals, including rotifers, nematodes, insects, and mites. The plant species that make galls also are diverse. We assume gall production costs the plant. All is well if the foreigner provides a gift that makes up for the cost. Nitrogen-fixing nodule-inducing bacteria provide nutritional services. Gall wasps pollinate fig trees. Unfortunately for plants, most galls are made for foes, some of which are deeply studied pathogens and pests: Agrobacterium tumefaciens, Rhodococcus fascians, Xanthomonas citri, Pseudomonas savastanoi, Pantoea agglomerans, 'Candidatus' phytoplasma, rust fungi, Ustilago smuts, root knot and cyst nematodes, and gall midges. Galls are an understudied phenomenon in plant developmental biology. We propose gall inception for discovering unifying features of the galls that plants make for friends and foes, talk about molecules that plants and gall-inducers use to get what they want from each other, raise the question of whether plants colonized by arbuscular mycorrhizal fungi respond in a gall-like manner, and present a research agenda.

Effect of Neuroterus quercusbaccarum (L.) galls on physiological and biochemical response of Quercus robur leaves

Gall formation is associated with multiple changes in plant cells, which still requires a better understanding. In this study, galls caused by sexual generation (♀♂) of Neuroterus quercusbaccarum (L.) (Hymenoptera: Cynipidae) on pedunculate oak trees (Quercus robur L.) were used as a model. Cytoplasmic membrane condition, concentration of hydrogen peroxide (H2O2), the activity of antioxidant enzymes and amino acid decarboxylase as well as chlorophyll fluorescence parameters were determined. Changes in physiological and biochemical parameters were analyzed in foliar tissues with galls and gall tissues themselves and compared to control. The presence of galls on oak leaves caused an increase of lipid peroxidation level. A significant decline in H2O2 and TBARS content with the reduction of guaiacol peroxidase (GPX) and ascorbate peroxidase (APX) activity were observed in gall tissues. The activity amino acid decarboxylase, i.e., LDC, ODC and TyDC varied between samples, which may affect the content of amino acids. The presence of N. quercusbaccarum galls caused an insignificant increase of the chlorophylls, carotenoids and anthocyanin contents, while the content of pigments and their ratios in gall tissues was extremely low. Moreover, photosynthetic parameters (F0, Fm, Fv/Fm, Y, qP) were significantly decreased. Data generated in this study indicate that the development of N. quercusbaccarum galls on pedunculate oak leaves has a negative effect on host plant related to the disruption of cell membrane integrity, disturbance of photosynthesis and reduction of the antioxidant potential of the host plant.

The induction and maintenance of in vitro plant morphogenesis as viewed from a new perspective, with theoretical and constructive implications

In plant tissue culture research, the non-traditional growth regulators, methylglyoxal and ascorbic acid, have been used to induce and promote in vitro morphogenesis from plant callus, generally having the initial characteristics of a type of neoplasm, and in many cases overcoming recalcitrant morphogenesis. In other investigations methylglyoxal, most likely with ascorbic acid, also promoted such morphogenesis. In the various investigations, low concentrations of methylglyoxal were used and proved to be the most effective in promoting in vitro morphogenesis. In many cases, the growth of such neoplastic-like calli was concurrently inhibited on culture media containing these chemicals. When methylglyoxal was present in high concentration, morphogenesis was also inhibited. Such chemicals, it would appear likely, allowed for the generation of cohesive forces within regions of the calli, reversing the neoplastic state in such regions, due to very low internal cohesion, and through such cohesive forces of particular magnitude, morphogenesis ensued, as an adaptive response to the stress of such cohesive forces. This would suggest a deeper, underlying biological process, with developmental features, that is perhaps universal among plants and perhaps in all biological organisms. This particular, consistent avenue and theme of plant tissue culture research, manifested over four decades and across four continents, may have revealed a unifying, dynamical process in both the biological and physical worlds, with constructive implications for agriculture and medicine.

Individual and Population Differences Shape Species Interactions and Natural Selection

Trait variation is central to our understanding of species interactions, and trait variation arising within species is increasingly recognized as an important component of community ecology. Ecologists generally consider intraspecific variation either among or within populations, yet these differences can interact to create patterns of species interactions. These differences can also affect species interactions by altering processes occurring at distinct scales. Specifically, intraspecific variation may shape species interactions simply by shifting a population's position along a trait-function map or by shifting the relationship between traits and their ecological function. I test these ideas by manipulating within- and among-population intraspecific variation in wild populations of a gall-forming insect before quantifying species interactions and phenotypic selection. Within- and among-population differences in gall size interact to affect attack rates by an enemy community, but among-population differences were far more consequential. Intraspecific differences shaped species interactions by both shifting the position of populations along the trait-function map and altering the relationship between traits and their function, with ultimate consequences for patterns of natural selection. I suggest that intraspecific variation can affect communities and natural selection by acting through individual- and population-level mechanisms.

Heritable Phytohormone Profiles of Poplar Genotypes Vary in Resistance to a Galling Aphid

Insect galls are highly specialized structures arising from atypical development of plant tissue induced by insects. Galls provide the insect enhanced nutrition and protection against natural enemies and environmental stresses. Galls are essentially plant organs formed by an intimate biochemical interaction between the gall-inducing insect and its host plant. Because galls are plant organs, their development is likely to be governed by phytohormones involved in normal organogenesis. We characterized concentrations of both growth and defensive phytohormones in ungalled control leaves and galls induced by the aphid Pemphigus betae on narrowleaf cottonwood Populus angustifolia that differ genotypically in resistance to this insect. We found that susceptible trees differed from resistant trees in constitutive concentrations of both growth and defense phytohormones. Susceptible trees were characterized by significantly higher constitutive cytokinin concentrations in leaves, significantly greater ability of aphids to elicit cytokinin increases, and significantly lower constitutive defense phytohormone concentrations than observed in resistant trees. Phytohormone concentrations in both constitutive and induced responses in galled leaves exhibited high broad-sense heritability that, respectively, ranged from 0.39 to 0.93 and from 0.28 to 0.66, suggesting that selection can act upon these traits and that they might vary across the landscape. Increased cytokinin concentrations may facilitate forming strong photosynthate sinks in the galls, a requirement for galling insect success. By characterizing for the first time the changes in 15 phytohormones belonging to five different classes, this study offers a better overview of the signaling alteration occurring in galls that has likely been important for their ecology and evolution. Copyright © 2019 The Author(s). This is an open-access article distributed under the CC BY-NC-ND 4.0 International license .

A Review of Galls on Ferns and Lycophytes

Fern-insect interactions have not received the same attention as angiosperm-insect interactions have. It has even been stated that ferns may have very few interactions with animals because of their lack of flowers, fruits, and seeds. Consequently, for many decades fern-insect interactions have been overlooked and underestimated, especially for highly developed interactions such as those with gall-formers. The present work aims to review the galls of ferns and lycophytes worldwide, to provide an updated checklist including unpublished data and to estimate the global gall diversity of ferns and lycophytes. We recorded 93 host species, belonging to 41 genera. Galls were found in 20 fern families and one lycophyte family (Selaginellaceae). Most galls occur within the more derived ferns of the order Polypodiales, especially the fern families Polypodiaceae (21 host species), Dryopteridaceae (14 host species) and Athyriaceae (11 host species). Thirty-eight of the 133 gall morphotypes were induced by mites and 95 by insects of six orders (Coleoptera, Diptera, Hymenoptera, Lepidoptera, Thysanoptera, and Hemiptera). Among the insects, Cecidomyiidae (Diptera) caused most of the galls (35 morphotypes). So far, most galls have been reported from the Neotropical region (40 spp.) and Oriental region (28 spp.).

Indirect Interactions Shape Selection in a Multispecies Food Web

Species do not live, interact, or evolve in isolation but are instead members of complex ecological communities. In ecological terms, complex multispecies interactions can be understood by considering indirect effects that are mediated by changes in traits and abundances of intermediate species. Interestingly, traits and abundances are also central to our understanding of phenotypic selection, suggesting that indirect effects may be extended to understand evolution in complex communities. Here we explore indirect ecological effects and their evolutionary corollary in a well-understood food web comprising a plant, its herbivores, and enemies that select for opposite defensive phenotypes in one of the herbivores. We show that ecological indirect interactions are mediated by changes to both the traits and the abundances of intermediate species and that these changes ultimately reduce enemy attack and weaken selection. We discuss the generality of the link between indirect effects and selection. We go on to argue that local adaptation and eco-evolutionary feedback may be less likely in complex multispecies food webs than in simpler food chains (e.g., coevolution). Overall, considering selection in complex interaction networks can facilitate the rapprochement of community ecology and evolution.

Biological control agent Rhizobium (=Agrobacterium) vitis strain ARK-1 suppresses expression of the essential and non-essential vir genes of tumorigenic R. vitis

OBJECTIVE

To gain insights into the virulence suppressive mechanism of a nonpathogenic strain of Rhizobium vitis ARK-1, we co-inoculated ARK-1 with a tumorigenic (Ti) strain of R. vitis to examine the expression of two essential virulence genes (virA and virG) and one non-essential gene (virD3) of the Ti strain at the wound site of grapevine.

RESULTS

Co-inoculation of ARK-1 with a Ti strain VAT03-9 at a 1:1 cell ratio into grapevine shoots resulted in significantly lower expression of the virulence genes virA, virD3, and virG of VAT03-9 at 1 day after inoculation compared with those when shoots were inoculated only with VAT03-9. ARK-1 was not able to catabolize acetosyringone, which is the plant-derived metabolites inducing the entire vir regulon in Ti strains, suggesting the direct effect of ARK-1 on the induction of broad range of vir genes of R. vitis Ti strains.

Eavesdropping on gall-plant interactions: the importance of the signaling function of induced volatiles

The galling insect manipulates the host plant tissue to its own benefit, building the gall structure where it spends during most of its life cycle. These specialist herbivore insects can induce and manipulate plant structure and metabolism throughout gall development and may affect plant volatile emission. Consequently, volatile emission from altered metabolism contribute to eavesdropping cueing. Eavesdropping can be part of adaptive strategies used by evolution for both galling insects and the entire-associated community in order to cue some interaction response. This is in contrast to some herbivores associated with delayed induced responses, altering plant metabolites during the short time while they feed. Due to the different lifestyles of the galling organism, which are associated with different plant tissues and organs (e.g leaves, flowers or fruits), a distinct diversity of organisms may eavesdrop on induced volatiles interacting with the galls. Furthermore, the eavesdropping cues may be defined according to the phenological coupling between galling organism and host plant, which results from the development of a gall structure. For instance, when plants release volatile-induced defenses after galling insects' activity, another interactor may perceive these volatiles and change its behavior and interactions with host plants and galls. Thus, natural enemies could be attracted by different volatiles emitted by the gall tissues. Considering the duration of the life cycle of the galling organism and the gall, the temporal extent of gall-induced volatiles may include more persistent volatile cues and eavesdropping effects than the volatiles induced by non-galling herbivores. Accordingly, from chemical ecology perspective we expect that galling herbivore-induced volatiles may exhibit robust effects on neighboring-plant interactions including those ones during different plant developmental or phenological periods. Information about multitrophic interactions between insects and plants supports the additional understanding of direct and indirect effects, and allows insight into new hypotheses.

Subtropical Interactions: Comparing Galling Insect and Host Plant Diversity in Southern Brazil and Florida

Gall-inducing insects seem to have a diversity pattern distinct from the usual latitudinal decrease in species, with more species occurring in xeric environments instead. Many questions regarding galler diversity over geographical scales remain unanswered: for example, little is known about beta diversity, and the role super host plants play in local/regional richness. Our aim was to compare galling insect and host plant diversity in different biogeographical regions, but under similar environmental conditions. We sampled short stature coastal woodlands on sandy soils of the Atlantic coast in both USA (Florida) and Brazil (Rio Grande do Sul, RS), between 25° and 30° latitude. Little-used 200-m long trails were searched during 90 min for galls; there were four trails in USA and five in Brazil. Gall functional traits (galled plant organ, gall shape and colour) proportions were not different between Florida and RS. Local galling and host plant species richness also did not differ, and neither did regional galling diversity. The beta diversity pattern, however, was distinct: sites in Florida have more similar galling faunas than sites in RS. Common diversity patterns indicate common environmental biotic (plant diversity, vegetation structure) and abiotic (climate, soil) factors might be contributing to these similar responses. As Brazilian sites are in the Atlantic forest hotspot, a high galling insect beta diversity might be caused by a higher heterogeneity at larger scales-sample-based rarefaction curves were ascending for Brazil, but not for USA. Myrtaceans were super hosts in Brazil, but not in Florida, where oaks take up this role.

The Gall Associates of Asphondylia poss. swaedicola Kieffer & Jörgensen (Diptera: Cecidomyiidae) on Suaeda divaricata Moq. (Amaranthaceae) in the Semiarid Argentina and Summary of Parasitic Hymenoptera Associated with Suaeda Worldwide

We report on Asphondylia poss. swaedicola Kieffer & Jörgensen inducing apical stem galls on Suaeda divaricata Moquin-Tandon in the Monte region of Argentina. The putative inquiline gelechiid Scrobipalpula patagonica Povolný is confirmed as an associate of A. poss. swaedicola galls. The following hymenopteran parasitoids are associated with this system: Torymus nr swaedicola (Kieffer & Jörgensen), Aprostocetus sp., Horismenus sp., Bracon (Bracon) sp., Chelonus (Microchelonus) sp., Apanteles sp., Zaeucoila robusta (Ashmead), and Goniozus nigrifemur Ashmead. The Horismenus sp., Z. robusta, and G. nigrifemur are reported as associates of Suaeda for the first time. A total of 28 genera and 31 species of parasitoids known to be associated with Suaeda spp. worldwide and their associations are tabulated.

Adaptive Divergence in a Defense Symbiosis Driven from the Top Down

Most studies of adaptive radiation in animals focus on resource competition as the primary driver of trait divergence. The roles of other ecological interactions in shaping divergent phenotypes during such radiations have received less attention. We evaluate natural enemies as primary agents of diversifying selection on the phenotypes of an actively diverging lineage of gall midges on tall goldenrod. In this system, the gall of the midge consists of a biotrophic fungal symbiont that develops on host-plant leaves and forms distinctly variable protective carapaces over midge larvae. Through field studies, we show that fungal gall morphology, which is induced by midges (i.e., it is an extended phenotype), is under directional and diversifying selection by parasitoid enemies. Overall, natural enemies disruptively select for either small or large galls, mainly along the axis of gall thickness. These results imply that predators are driving the evolution of phenotypic diversity in symbiotic defense traits in this system and that divergence in defensive morphology may provide ecological opportunities that help to fuel the adaptive radiation of this genus of midges on goldenrods. This enemy-driven phenotypic divergence in a diversifying lineage illustrates the potential importance of consumer-resource and symbiotic species interactions in adaptive radiation.

Reproductive Biology of Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae)

Leptocybe invasa Fisher & La Salle (Hymenoptera: Eulophidae) is an invasive pest in Eucalyptus plantations around the world. The successful colonization of L. invasa is possibly related to its reproductive biology. The objective of this study was to examine the reproductive biology of L. invasa. In Guangxi Province, the sex ratio (proportion of female, 0.99) of L. invasa was female-dominant throughout the year based on natural and artificial infestation. This result was similar to the ratios observed for other geographic populations in China, including those in Fujian (0.99), Guangdong (0.98), Hainan (0.95), Jiangxi (0.96), and Sichuan (0.99). The offspring sex ratio favored females. A large number of females emerged from the galls produced by females, with few males found. Galls on the petioles and midribs of Eucalyptus plants could be caused by newly emerged females with mature eggs. The lengths of the ovariole, spermatheca, common oviduct, and reproductive glands did not differ among L. invasa females, but their lateral oviducts showed differences from 0 to 42 h after emergence, indicating that this insect is proovigenic. These results could explain why L. invasa populations can rapidly increase in invaded areas.

Galling Insects of the Brazilian Páramos: Species Richness and Composition Along High-Altitude Grasslands

In this work, we investigated the factors that determine the distribution of galling insects in high-altitude grasslands, locally called 'campos de altitude' of Mantiqueira Range and tested whether 1) richness of galling insects decreases with altitude, 2) galling insect richness increases with plant richness, 3) variation in galling insect diversity is predominantly a consequence of its β component, and 4) turnover is the main mechanism driving the beta diversity of both galling insects and plants. Galling insect richness did not exhibit a negative relationship with altitude, but it did increase with plant richness. The additive partition of regional richness (γ) into its local and beta components showed that local diversity (α) of galling insects and plants was relatively low in relation to regional diversity; the β component incorporated most of the regional diversity. This pattern was also found in the multiscale analysis of the additive partition for galling insects and plants. The beta diversity of galling insects and plants was driven predominantly by the process of turnover and minimally by nesting. The results reported here point out that the spatial distribution of galling insects is best explained by historical factors, such as the distribution of genera and species of key host plants, as well as their relation to habitat, than ecological effects such as hygrothermal stress - here represented by altitude.