Renê Gonçalves da Silva Carneiro

Do Cecidomyiidae galls of Aspidosperma spruceanum (Apocynaceae) fit the pre-established cytological and histochemical patterns?

Cecidomyiidae galls commonly present a zonation of tissues with lignified cell layers externally limiting a reserve tissue and internally limiting a specialized nutritive tissue next to the larval chamber. The cytological aspects of this specialized tissue indicate high metabolic activity as well as carbohydrate accumulation. In Aspidosperma spruceanum–Cecidomyiidae gall system, ultrastructural and histochemical investigations corroborated this pattern and also revealed the storage of proteins in the nutritive cells. Reactive oxygen species (ROS), callose, and pectin accumulation were related to the feeding activity of the galling herbivore. Phosphorylase, glucose-6-phosphatase, acid phosphatases, invertases, and sucrose synthase activities were detected for the first time, in the Neotropical region, and discussed in relation to gall maintenance and the feeding activity of the Cecidomyiidae.

Manipulation of host plant cells and tissues by gall-inducing insects and adaptive strategies used by different feeding guilds

Biologists who study insect-induced plant galls are faced with the overwhelming diversity of plant forms and insect species. A challenge is to find common themes amidst this diversity. We discuss common themes that have emerged from our cytological and histochemical studies of diverse neotropical insect-induced galls. Gall initiation begins with recognition of reactive plant tissues by gall inducers, with subsequent feeding and/or oviposition triggering a cascade of events. Besides, to induce the gall structure insects have to synchronize their life cycle with plant host phenology. We predict that reactive oxygen species (ROS) play a role in gall induction, development and histochemical gradient formation. Controlled levels of ROS mediate the accumulation of (poly)phenols, and phytohormones (such as auxin) at gall sites, which contributes to the new cell developmental pathways and biochemical alterations that lead to gall formation. The classical idea of an insect-induced gall is a chamber lined with a nutritive tissue that is occupied by an insect that directly harvests nutrients from nutritive cells via its mouthparts, which function mechanically and/or as a delivery system for salivary secretions. By studying diverse gall-inducing insects we have discovered that insects with needle-like sucking mouthparts may also induce a nutritive tissue, whose nutrients are indirectly harvested as the gall-inducing insects feeds on adjacent vascular tissues. Activity of carbohydrate-related enzymes across diverse galls corroborates this hypothesis. Our research points to the importance of cytological and histochemical studies for elucidating mechanisms of induced susceptibility and induced resistance.

Cytological and histochemical gradients on two Copaifera langsdorffii Desf. (Fabaceae)—Cecidomyiidae gall systems

Previous ultrastructural and histochemical analysis proposed patterns in the accumulation of substances in galls of Diptera: Cecidomyiidae in some plant species of the temperate region. Similar analyses were done to verify the conservativeness of these patterns in the Neotropical region, where a great number of species of Cecidomyiidae is responsible for a wide diversity of morphotypes. Two gall morphotypes induced by Cecidomyiidae in a unique host plant, Copaifera langsdorffii, were studied. The gradients of carbohydrates and the activity of invertases and acid phosphatases were similar, but the cytological gradients and distribution of proteins evidenced that the sites of the induction as well as the amount of neoformed tissues may be peculiar to each gall system. The production of lipids just in the secretory cavities either in the non-galled or galled tissues indicated a potentiality of the host plant which could not be manipulated by the galling insects. Further, the absence of nucleus in the nutritive tissue, an exclusive feature of the horn-shaped galls, indicates cell death attributed to the feeding habit of the galling herbivore.

The imbalance of redox homeostasis in arthropod-induced plant galls: Mechanisms of stress generation and dissipation☆

BACKGROUND Galls have specialized tissues for the protection and nutrition of the inducers, and these tissues have been studied from the developmental and histochemical perspectives. Recently, the role of oxidative stress in galls has been tested histochemically through detection of H2O2 in gall tissues. SCOPE OF REVIEW Developmental processes and cytological events are revisited from the perspective of the redox-potential balance in both the apoplast and symplast, especially concerning the accumulation of reactive oxygen species (ROS). MAJOR CONCLUSIONS The redox potential is imbalanced differently in the apoplast and symplast at gall sites, with the apoplast having lower antioxidant-buffering capacity than the symplast. The strategies to recover redox-potential homeostasis involve the dissipation of ROS by scavenging molecules, such as phenolics, flavonoid derivatives, tocopherol, and enzyme systems. GENERAL SIGNIFICANCE Insect galls are good models to test developmental hypotheses. Although the exact mechanisms of gall induction and development have not been elucidated at the biochemical and biophysical levels, modulation of the redox potential is involved in the crucial steps of gall initiation and establishment. This article is part of a Special Issue entitled Redox regulation of differentiation and de-differentiation.

Developmental anatomy and immunocytochemistry reveal the neo-ontogenesis of the leaf tissues of Psidium myrtoides (Myrtaceae) towards the globoid galls of Nothotrioza myrtoidis (Triozidae).

Key messageThe temporal balance between hyperplasia and hypertrophy, and the new functions of different cell lineages led to cell transformations in a centrifugal gradient that determines the gall globoid shape.AbstractPlant galls develop by the redifferentiation of new cell types originated from those of the host plants, with new functional and structural designs related to the composition of cell walls and cell contents. Variations in cell wall composition have just started to be explored with the perspective of gall development, and are herein related to the histochemical gradients previously detected on Psidium myrtoides galls. Young and mature leaves of P. myrtoides and galls of Nothotrioza myrtoidis at different developmental stages were analysed using anatomical, cytometrical and immunocytochemical approaches. The gall parenchyma presents transformations in the size and shape of the cells in distinct tissue layers, and variations of pectin and protein domains in cell walls. The temporal balance between tissue hyperplasia and cell hypertrophy, and the new functions of different cell lineages led to cell transformations in a centrifugal gradient, which determines the globoid shape of the gall. The distribution of cell wall epitopes affected cell wall flexibility and rigidity, towards gall maturation. By senescence, it provided functional stability for the outer cortical parenchyma. The detection of the demethylesterified homogalacturonans (HGAs) denoted the activity of the pectin methylesterases (PMEs) during the senescent phase, and was a novel time-based detection linked to the increased rigidity of the cell walls, and to the gall opening. Current investigation firstly reports the influence of immunocytochemistry of plant cell walls over the development of leaf tissues, determining their neo-ontogenesis towards a new phenotype, i.e., the globoid gall morphotype.

Could the Extended Phenotype Extend to the Cellular and Subcellular Levels in Insect-Induced Galls?

Neo-ontogenesis of plant galls involves redifferentiation of host plant tissues to express new phenotypes, when new cell properties are established via structural-functional remodeling. Herein, Psidium cattleianum leaves and Nothotrioza cattleiani galls are analyzed by developmental anatomy, cytometry and immunocytochemistry of cell walls. We address hypothesis-driven questions concerning the organogenesis of globoid galls in the association of P. cattleianum - N. cattleianum, and P. myrtoides - N. myrtoidis. These double co-generic systems represent good models for comparing final gall shapes and cell lineages functionalities under the perspective of convergent plant-dependent or divergent insect-induced characteristics. Gall induction, and growth and development are similar in both galls, but homologous cell lineages exhibit divergent degrees of cell hypertrophy and directions of elongation. Median cortical cells in P. cattleianum galls hypertrophy the most, while in P. myrtoides galls there is a centrifugal gradient of cell hypertrophy. Cortical cells in P. cattleianum galls tend to anisotropy, while P. myrtoidis galls have isotropically hypertrophied cells. Immunocytochemistry evidences the chemical identity and functional traits of cell lineages: epidermal cells walls have homogalacturonans (HGAs) and galactans, which confer rigidity to sites of enhanced cell division; oil gland cell walls have arabinogalactan proteins (AGPs) that help avoiding cell death; and parenchyma cell walls have HGAs, galactans and arabinans, which confer porosity. Variations in such chemical identities are related to specific sites of hypertrophy. Even though the double co-generic models have the same macroscopic phenotype, the globoid morphotype, current analyses indicate that the extended phenotype of N. cattleiani is substantiated by cellular and subcellular specificities.

Gall Morphotypes in the Neotropics and the Need to Standardize Them

A morphotype can be defined as a specimen that illustrates a morphological variation within a species or, in the case of galls, a characteristic neo-formed plant organ generated by the interaction between a gall-inducing organism and a host plant. Once each gall morphotype is unique and derived from a species-specific interaction, there is a great confidence in using them to identify the different galling systems. In the Neotropics, where the biodiversity is high but somewhat unknown from the taxonomical point of view, the use of morphotypes helps assessing the abundance and richness of galling herbivores. This kind of knowledge would remain inaccessible if its report depended strictly on the taxonomic identification of the involved taxa. An effort on the standardization of the nomenclature used for inventories in the Neotropics revealed that some tridimensional shapes such as the globoid, ellipsoid, and lenticular are quite common, and may be the result of a series of similar events of cell division and expansion. When these morphotypes concomitantly occur on super-hosts of galling herbivores, special attention should be given to the possibility of overestimations, because variables such as the developmental stage of the gall, the age of the host organ by the time of oviposition, as well as morphological variations related to the sex of the inducer may be difficult to be visualized. In specific cases, the phenological and anatomical analyses are crucial to avoid misinterpretations.

Gradients of metabolite accumulation and redifferentiation of nutritive cells associated with vascular tissues in galls induced by sucking insects.

Galls are structures entirely made of plant tissues manipulated by gall-inducing parasites. We analyzed the alterations of cell phenotypes caused by a sucking-insect, Nothotrioza cattleiani, on the leaves of Psidium cattleianum that led to the formation of a globoid gall morphotype. We found changed cell fates in the leaves compared to the galls, and different degrees of cell alterations in gall layers, which formed gradients. Surprisingly, the vascular parenchyma cells on N. cattleiani galls are nutritive. Herein, we show that even though the globoid shape is one of the most common in nature, the galls of N. cattleiani are unique entities.

Developmental Anatomy of Galls in the Neotropics: Arthropods Stimuli Versus Host Plant Constraints

As natural microlaboratories, galls are elegant models to study plant cell fates. Each gall morphotype is the product of repetitive patterns in cell division and differentiation, which culminate in a neoformed multicellular organ. Gall morphogenesis ruptures the patterns of cell polarization and expansion in relation to their host organs through cell redifferentiation, which results in changes in their functionality. As so, gall tissues guarantee nutrition, protection and a favorable microenvironment to the gall inducer. Sites of hyperplasia and hypertrophy are commonly reported for arthropod galls, and are commonly related to the feeding habits of each taxon. Nevertheless, there are some morphotypes in which the shapes are so peculiar that some other mechanisms must be involved, such as biochemical interactions, for instance. We revisit some Neotropical gall systems to check if the accumulation of phenolics is kept as one of the first cell responses to the presence of the inducer and if it is related to the changes in cell polarity and axiality. The final gall morphotypes require new spatial and developmental control of the host plant cells division and expansion, together with cell redifferentiation, but under the constraints imposed by the host plant organs.

Multivesicular bodies differentiate exclusively in nutritive fast-dividing cells in Marcetia taxifolia galls.

Marcetia taxifolia (A. St.-Hil.) DC. hosts two gall morphotypes, a pistil-shaped gall induced by a Cecidomyiidae (Diptera) and a fusiform stem gall induced by a Lepidoptera. The cytological study of these galls aimed to answer how the difference in nutritive tissues of Diptera and Lepidoptera galls could be explained on cytological basis. The nutritive tissues of lepidopteran galls have a fast-dividing cell zone, the storage nutritive tissue, which replaces the cells of the typical nutritive tissue, where the larvae feed. The differentiation of multivesicular bodies in the plasma membrane occurred exclusively in these fast-dividing cells of the lepidopteran galls, evidencing the meristematic condition of such tissue. The accumulation of reactive oxygen species (ROS) analyzed in situ in the nutritive cells is not sufficient to induce programmed cell death (PCD), as the cells of M. taxifolia have plastoglobules and accumulate polyphenols and terpenoids, which are diagnostic defenses against oxidative stress. The two taxa of galling insects have different nutritional requirements, thus inducing specific cytoplasm-enriched cells on their nutritive tissues.