Gracielle Pereira Pimenta Bragança

Bio: Gracielle Pereira Pimenta Bragança is an academic researcher from Universidade Federal de Minas Gerais. The author has contributed to research in topics: Gall & Cecidomyiidae. The author has an hindex of 6, co-authored 10 publications receiving 95 citations.

Feeding and Other Gall Facets: Patterns and Determinants in Gall Structure

Abstract: Galls are neoformed structures induced by specific animals, fungi, bacteria, virus or some parasitic plants on their host plant organs. Developmental processes are well known in Agrobacterium tumefasciens galls, but the animal-induced galls have a striking anatomical diversity, concerning several patterns, which were reunited herein. Anatomical traits observed in animal-induced galls involve manipulation of plant morphogenesis in convergent ways. Nematode, mite and insect galls usually contain homogeneous storage parenchyma and develop due to hyperplasia and cell hypertrophy. The development of typical nutritive tissues, giant cells, or hypertrophied vascular bundles may occur. Some other anatomical features may be usually restricted to galls induced by specific taxa, but they may eventually be related to the developmental potentialities of the host plants. The combination of distinct morphogenetic peculiarities in each gall system culminates in extant gall structural diversity. Convergent anatomical traits are observed according to the feeding mode of the gall inducers, representing potentiation or inhibition of similar events of host plant morphogenesis and cell redifferentiation, independent of gall-inducing taxa.

Compartmentalization of Metabolites and Enzymatic Mediation in Nutritive Cells of Cecidomyiidae Galls on Piper Arboreum Aubl. (Piperaceae)

Abstract: Galling insects commonly change the chemical profile of their host plant tissues during gall induction and establishment. As a consequence, galls accumulate a wide range of metabolites in specialized cells, which may be organized in a nutritive tissue and in outer storage cells. The nutrients compartmentalized in nutritive cells may be directly assessed or metabolized via enzymatic mediation, while the gall outer cortex may accumulate secondary metabolites. These secondary metabolitesmay configure a specialized chemical barrier against the attack of natural enemies. Either the nutritive inner cells or the outer cortical cells, with their specific metabolic apparatus, should differentiate under the chemical constraints of each host plant-galling herbivore interaction. This premise is herein addressed by the investigation of the histochemical profile of the non-galled leaves and galls induced by Diptera: Cecidomyiidae on Piper arboreum. The spatial compartmentalization of the nutritive and defensive metabolites indicates the new functions assumed during the redifferentiation of the host plant cells. The enzymatic mediation of the primary metabolites by sucrose synthase and invertases favors the nutritive requirements of the galling Cecidomyiidae or the structural maintenance of the gall. The accumulation of secondary metabolites is restrict to the tissue layers not involved in nutrition, and may act in the chemical protection against predators or parasitoids. Current results systematically document metabolites compartmentalization, evidence the impairment of toxic compounds storage in cells surrounding the larval chamber, as well as, detect the redirection of nutritive substances to the site of the Cecidomyiidae feeding. The activity of sucrose synthase is restrict to the nutritive tissue in the galls on Piper arboreum, and reinforces previous detection of this enzyme mediation in carbohydrate metabolism in Cecidomyiidae galls.

Influence of auxin and phenolic accumulation on the patterns of cell differentiation in distinct gall morphotypes on Piptadenia gonoacantha (Fabaceae)

Abstract: The cascade of biochemical changes occurring at sites of gall development seems to involve a group of common metabolites in plants, namely, the phenolics. Phenolic accumulation has been commonly related to chemical defence, but their primary role seems to be the regulation of cell hypertrophy in galls. Such regulation implies phenolics–auxin (IAA) association at some cell re-differentiation sites, and determines final gall shapes. Herein, we investigated phenolic and auxin accumulation in four gall systems, grouped in two morphotypes, namely lenticular and globoid, induced on pinnulas of Piptadenia gonoacantha (Mart.) J.F.Macbr. Changes in the direction and type of cell expansion between non-galled pinnula and galls were also evaluated. Galling insects associated to lenticular and globoid gall morphotypes promoted changes in host plant cells, leading to the development of different cell sizes, different degrees of anisotropy, and different directions of cell expansion. The accumulation of IAA–phenolics compartmentalised on the basis of gall morphotype, i.e. in the cells of superior and lateral inferior cortices in the lenticular gall morphotypes, and throughout the outer cortex in the globoid gall morphotypes. The sites of accumulation of IAA and phenolics coincided with the most hypertrophied regions, influencing on the determination of the final gall shape.

Cytological attributes of storage tissues in nematode and eriophyid galls: pectin and hemicellulose functional insights

Abstract: Cell walls and protoplast may work together or distinctly in the establishment of the functional profiles of gall tissue compartments. This presumption is herein evaluated in three gall systems by immunocytochemical and ultrastructural analyses. The common storage tissues (CSTs) of leaf galls induced by Eriophyidae on Miconia ibaguensis leaves and by Ditylenchus gallaeformans on M. ibaguensis and M. albicans have rigid and porous cell walls due to their composition of pectins. Hemicelluloses in CST cell walls are scarcer when compared to the cell walls of the control leaves, being functionally compensated by rigid pectate gels. The typical nutritive tissues (TNTs) in galls induced by Ditylenchus gallaeformans are similar to promeristematic and secretory cells regarding their enriched cytoplasm, several mitochondria, and proplastids, as well as multivesicular and prolamellar bodies in cell membranes. The cytological features of the feeding cells of Eriophyidae galls indicate that they are not as metabolically active as the cells of the TNT in nematode galls. However, their cell wall composition suggests more plasticity and porosity than the cells of the TNT, which can compensate the less production of nutrients with more transport. The ultrastructural and immunocytochemical profiles of CST cells reveal functional similarities, which are independent of the taxa of the gall inducer or of the host plant. Despite their analogous functionalities, the protoplast and cell wall features of TNT cells of nematode galls and of the feeding cells of the Eriophyidae galls are distinct, and work out through different strategies toward keeping gall developmental site active.

Enzyme‐mediated metabolism in nutritive tissues of galls induced by Ditylenchus gallaeformans (Nematoda: Anguinidae)

Abstract: The galls induced by Ditylenchus gallaeformans (Nematoda) on leaves of Miconia albicans have unique features when compared to other galls. The nematode colonies are surrounded by nutritive tissues with promeristematic cells, capable of originating new emergences facing the larval chamber, and providing indeterminate growth to these galls. Considering enzyme activity as essential for the translocation of energetic molecules from the common storage tissue (CST) to the typical nutritive tissue (TNT), and the major occurrence of carbohydrates in nematode galls, it was expected that hormones would mediate sink strength relationships by activating enzymes in indeterminate growth regions of the galls. Histochemical, immunocytochemical and quantitative analyses were made in order to demonstrate sites of enzyme activity and hormones, and comparative levels of total soluble sugars, water soluble polysaccharides and starch. The source-sink status, via carbohydrate metabolism, is controlled by the major accumulation of cytokinins in totipotent nutritive cells and new emergences. Thus, reducing sugars, such as glucose and fructose, accumulate in the TNT, where they supply the energy for successive cycles of cell division and for nematode feeding. The histochemical detection of phosphorylase and invertase activities indicates the occurrence of starch catabolism and sucrose transformation into reducing sugars, respectively, in the establishment of a gradient from the CST towards the TNT. Reducing sugars in the TNT are important for the production of new cell walls during the indeterminate growth of the galls, which have increased levels of water-soluble polysaccharides that corroborate such a hypothesis. Functional relationship between plant hormone accumulation, carbohydrate metabolism and cell differentiation in D. gallaeformans-induced galls is attested, providing new insights on cell development and plant metabolism.

The Cell Wall

Abstract: Secondary thickening in pteridophytes.-The known cases of secondary thickening in recent Pteridophyta have been brought together by HILL23 in a useful resume. After stating the criteria for secondary growth, Botrychium, which has a distinct cambium, and Ophioglossum, which lacks a definite layer, are described, followed by Angiopteris and Marattia, in which a cambium forms a few xylem elements. CORMACK'S observations on the secondary wood in the nodes of Equisetum are cited, though no reference is made to the cambium in the young cone as reported by J]FFREY.24 The other cases of secondary growth include Psilotum, Selaginella spinulosa, and several species of Isoetes, especially I. hystrix, which may show a cambium outside the vascular cylinder.-M. A.

Feeding and Other Gall Facets: Patterns and Determinants in Gall Structure

Abstract: Galls are neoformed structures induced by specific animals, fungi, bacteria, virus or some parasitic plants on their host plant organs. Developmental processes are well known in Agrobacterium tumefasciens galls, but the animal-induced galls have a striking anatomical diversity, concerning several patterns, which were reunited herein. Anatomical traits observed in animal-induced galls involve manipulation of plant morphogenesis in convergent ways. Nematode, mite and insect galls usually contain homogeneous storage parenchyma and develop due to hyperplasia and cell hypertrophy. The development of typical nutritive tissues, giant cells, or hypertrophied vascular bundles may occur. Some other anatomical features may be usually restricted to galls induced by specific taxa, but they may eventually be related to the developmental potentialities of the host plants. The combination of distinct morphogenetic peculiarities in each gall system culminates in extant gall structural diversity. Convergent anatomical traits are observed according to the feeding mode of the gall inducers, representing potentiation or inhibition of similar events of host plant morphogenesis and cell redifferentiation, independent of gall-inducing taxa.

Functional compartmentalisation of nutrients and phenolics in the tissues of galls induced by Leptocybe invasa (Hymenoptera: Eulophidae) on Eucalyptus camaldulensis (Myrtaceae)

Abstract: Galling herbivores induce structural and chemical alterations in their host plant's tissues. These insects have been the focus of little study in the case of Australian taxa. Leptocybe invasa, a native Australian galling hymenopteran associated with Eucalyptus species, causes economic damage to plantation eucalypts in many countries around the world. Leptocybe invasa oviposits in the midribs and petioles of expanding leaves thereby intercepting photosynthates and impairing normal expansion. We analysed the ultrastructural and chemical cellular changes in L. invasa galls on Eucalyptus camaldulensis (probably subspecies camaldulensis) to diagnose how the insect manipulates plant cells and tissues and the significance of these alterations for insect nutrition and protection. Galling stimuli induce the formation of two functionally compartmentalised types of tissue. Phenolic plant secondary metabolites and anthocyanins (plant pigments) accumulate in the outer compartment, while primary metabolites accumulate in the inner compartment. The nutritive cells (inner compartment) accumulate protein and lipids that provide food for the larvae. Total polyphenol concentrations did not differ significantly between outer and inner compartments. Nevertheless, the concentrations of quercetin and kaempferol derivatives were higher in the outer compartment than in the inner compartment. These differences could be related to the protection of plant tissues against ultraviolet rays and the maintenance of redox homeostasis. There were higher ratios of hexahydroxydiphenoyl‐containing hydrolysable tannins rather than galloyl‐containing hydrolysable tannins in the inner compartment. This shift in the oxidative capacity of the polyphenols in the inner compartment could represent a defensive plant response to the larvae.

Reacquisition of New Meristematic Sites Determines the Development of a New Organ, the Cecidomyiidae Gall on Copaifera langsdorffii Desf. (Fabaceae).

Abstract: The development of gall shapes has been attributed to the feeding behavior of the galling insects and how the host tissues react to galling stimuli, which ultimately culminate in a variable set of structural responses. A superhost of galling herbivores, Copaifera langsdorffii, hosts a bizarre “horn-shaped” leaflet gall morphotype induced by an unidentified species of Diptera: Cecidomyiidae. By studying the development of this gall morphotype under the anatomical and physiological perspectives, we demonstrate the symptoms of the Cecidomyiidae manipulation over plant tissues, toward the cell redifferentiation and tissue neoformation. The most prominent feature of this gall is the shifting in shape from growth and development phase toward maturation, which imply in metabolites accumulation detected by histochemical tests in meristem-like group of cells within gall structure. We hypothesize that the development of complex galls, such as the horn-shaped demands the reacquisition of cell meristematic competence. Also, as mature galls are green, their photosynthetic activity should be sufficient for their oxygenation, thus compensating the low gas diffusion through the compacted gall parenchyma. We currently conclude that the galling Cecidomyiidae triggers the establishment of new sites of meristematic tissues, which are ultimately responsible for shifting from the young conical to the mature horn-shaped gall morphotype. Accordingly, the conservative photosynthesis activity in gal site maintains tissue homeostasis by avoiding hypoxia and hipercarbia in the highly compacted gall tissues.