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

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.

How the activity of natural enemies changes the structure and metabolism of the nutritive tissue in galls? Evidence from the Palaeomystella oligophaga (Lepidoptera) -Macairea radula (Metastomataceae) system.

Insect-induced galls usually develop nutritional cells, which they induce and consume directly, and any metabolic modification of those cells may reflect changes of the insect's own metabolism. The system Palaeomystella oligophaga (Lepidoptera)-Macairea radula (Melastomataceae) presents a series of natural enemies, including parasitoids and cecidophages that can function as a natural experiment, respectively removing the specific galling feeding stimulus and providing a nonspecific one. Considering that the process of induction and maintenance of gall tissues strictly depends on the constant specific stimulus of galling, question I:What kind of metabolic changes these different groups of natural enemies can promote in chemical and structural composition of these galls? II: How the specialized tissues are metabolically dependent on the constant specific stimulus of galling in latter stages of gall development? Galls without natural enemies, with parasitoids or cecidophages in larvae or pupae stages were analyzed through histochemistry and cytological profiles and all compared to galls in natural senescence state. The analysis revealed the accumulation of proteins and lipids in typical nutritive tissue and starch in the storage tissue, as well a high integrity of cellular organelles and membrane systems on galls with gallings in the larval stage. Both parasitoids and cecidophages stop galling feeding activities, which resulted in the paralysis of the stimulus that maintain the metabolism of gall tissues, leading to generalized collapse. We demonstrate that the development and metabolic maintenance of a typical nutritive tissue in these galls are completely dependent on constant larval stimulus.

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.

The redifferentiation of nutritive cells in galls induced by Lepidoptera on Tibouchina pulchra (Cham.) Cogn. reveals predefined patterns of plant development.

Insect galls may present nutritive tissues with distinct cytological features related to the order of the gall inducer. Galling Lepidoptera larvae chew plant cells and induce the redifferentiation of parenchymatic cells into nutritive ones. The nutritive cells in the galls induced by a microlepidoptera on the leaves of Tibouchina pulchra (Cham.) Cogn. (Melastomataceae) are organelle-rich, with developed Golgi apparatus, endoplasmic reticulum, ribosomes, polyribosomes, mitochondria, plastids, and one great central or several fragmented vacuoles. The nonobservance of the nuclei in the nutritive cells deserves special attention, and confers a similarity between the nutritive cells and the vascular conductive ones. The great amount of rough endoplasmic reticulum, ribosomes, polyribosomes, and mitochondria is indicative of the high metabolic status of these cells. They are vascular cambium-like, with high protein synthesis and lipid storage. The proteins are essential to enzymatic metabolism, and secondarily, to larvae nutrition, similarly to the lipid droplets which confer energetic profile to these nutritive cells. The living enucleated cells receive mRNA from their neighbor ones, which may support the high metabolic profile of endoplasmic reticulum and ribosomes observed in galls. Thus, the nutritive cells are stimulated by the galling larvae activity, generating a new cell type, whose redifferentiation includes a mix of intrinsic and common plant pathways.

Effects of abiotic stress on biomass and anthocyanin production in cell cultures of Melastoma malabathricum.

Plant cell cultures could be used as an important tool for biochemical production, ranging from natural coloring (pigments) to pharmaceutical products. Anthocyanins are becoming a very important alternative to synthetic dyes because of increased public concern over the safety of artificial food coloring agents. Several factors are responsible for the production of anthocyanin in cell cultures. In the present study, we investigate the effects of different environmental factors, such as light intensity, irradiance (continuous irradiance or continuous darkness), temperature and medium pH on cell biomass yield and anthocyanin production in cultures of Melastoma malabathricum. Moderate light intensity (301 - 600 lux) induced higher accumulation of anthocyanins in the cells. The cultures exposed to 10-d continuous darkness showed the lowest pigment content, while the cultures exposed to 10-d continuous irradiance showed the highest pigment content. The cell cultures incubated at a lower temperature range (20 ± 2 ºC) grew better and had higher pigment content than those grown at 26 ± 2 ºC and 29 ± 2 ºC. Different medium pH did not affect the yield of cell biomass but anthocyanin accumulation was highest at pH 5.25 - 6.25.

Effects of abiotic stress on biomass and anthocyanin production in cell cultures of Melastoma malabathricum

Plant cell cultures could be used as an important tool for biochemical production, ranging from natural coloring (pigments) to pharmaceutical products. Anthocyanins are becoming a very important alternative to synthetic dyes because of increased public concern over the safety of artificial food coloring agents. Several factors are responsible for the production of anthocynin in cell cultures. In the present study, we investigate the effects of different environmental factors, such as light intensity, irradiance (continuous irradiance or continuous darkness), temperature and medium pH on cell biomass yield and anthocyanin production in cultures of Melastoma malabathricum. Moderate light intensity (301 - 600 lux) induced higher accumulation of anthocyanins in the cells. The cultures exposed to 10-d continuous darkness showed the lowest pigment content, while the cultures exposed to 10-d continuous irradiance showed the highest pigment content. The cell cultures incubated at a lower temperature range (20 ± 2 ºC) grew better and had higher pigment content than those grown at 26 ± 2ºC and 29 ± 2ºC. Different medium pH did not affect the yield of cell biomass but anthocyanin accumulation was highest at pH 5.25 - 6.25.

Leaf emergences in Microlepis oleaefolia (DC.) Triana (Melastomataceae) and their probable function: an anatomical and ultrastructural study.

Microlepis oleaefolia (DC.) Triana, an endemic species of Melastomataceae from the Brazilian cerrado, presents very complex leaf structures called as "hairs with root-like base" embedded in the mesophyll. This paper describes the ontogenesis, histochemical and structural aspects of these leaf structures as a framework for further functional studies. Samples of leaves in different developmental stages were processed according to common light and electron microscopy techniques. Fresh material was subjected to histochemical tests to examine the chemical composition of cell walls. The apoplastic transport between leaf emergences and the vascular system was verified by staining with 1% aqueous safranin. The structures are emergences of mixed protoderm and ground meristem origin. They are persistent, predominantly short-stalked and dendritic. Their arms have thick non-lignified cellulosic walls with a loose and heterogeneous aspect; on the inner face, the wall, which appears labyrinthine, presents small irregularly shaped projections directed towards the protoplast. The base of the emergences is composed of sclereids embedded in the mesophyll that reach the vascular system. Assays with aqueous safranin solution revealed it penetrates the cell walls of the arms and showed a connection between the emergence and xylem. Anatomical, chemical and ultrastructural features of leaf emergences of M. oleaefolia indicate that these structures are able to transport substances via apoplast and can absorb or exude solutions.