Luiz Alfredo Rodrigues Pereira

The N protein of Tomato spotted wilt virus (TSWV) is associated with the induction of programmed cell death (PCD) in Capsicum chinense plants, a hypersensitive host to TSWV infection.

In sweet pepper, the Tsw gene, originally described in Capsicum chinense, has been widely used as an efficient gene for inducing a hypersensitivity response (HR) derived Tomato spotted wilt virus (TSWV) resistance. Since previously reported studies suggested that the TSWV-S RNA mutation(s) are associated with the breakdown of Tsw mediated TSWV resistance in peppers, the TSWV genes N (structural nucleocapsid protein) and NS(S) (non-structural silencing suppressor protein) were cloned into a Potato virus X (PVX)-based expression vector, and inoculated into the TSWV-resistant C. chinense genotype, PI 159236, to identify the Tsw-HR viral elicitor. Typical HR-like chlorotic and necrotic lesions followed by leaf abscission were observed only in C. chinense plants inoculated with the PVX-N construct. Cytopathological analyses of these plants identified fragmented genomic DNA, indicative of programmed cell death (PCD), in mesophyll cell nuclei surrounding PVX-N-induced necrotic lesions. The other constructs induced only PVX-like symptoms without HR-like lesions and there were no microscopic signs of PCD. The mechanism of TSWV N-gene HR induction is apparently species specific as the N gene of a related tospovirus, Tomato chlorotic spot virus, was not a HR elicitor and did not cause PCD in infected cells.

Micropropagation of Alibertia edulis Rich

ABSTRACT The aim of this work was to develop a micropropagation protocol for Alibertia edulis, a medicinal Brazilian Cerrado plant. A. edulis seeds were sterilized and germinated in water-agar. Fifteen millimeter long explants from the seedlings cultivated for 50 days were used for the multiplication in three consecutive subcultures. The cytokinin benzyladenine (BA) alone or combined with indole-3-butyric acid (IBA) was added to ¼ MS medium. The treatments containing combinations of the BA + IBA induced more shoot proliferation than the BA alone, with the optimum concentration of 0.5 mg.L -1 for both growth regulators. A. edulis shoots elongated easily and the presence of growth regulators did have a positive effect on the shoot elongation. Consecutive subcultures also had a positive effect on both sprouting and shoot elongation. Activated charcoal was essential for rooting, and all rooted plants were able to acclimatize. Key words: Cerrado, Alibertia edulis , rooting, germination, activated charcoal

Comparative Anatomy of the Bark of Stems, Roots and Xylopodia of Brosimum Gaudichaudii (Moraceae)

Brosimum gaudichaudii Trec. occurs in the Atlantic and Amazon forests, and is the only species of Brosimum commonly found in Cerrado vegetation. It is of pharmaceutical interest due to the large accumulation of furocoumarins such as psoralens in the bark of roots and xylopodia. This work describes the bark anatomy of sterns, roots, and xylopodia. Although the external bark morphology of stern and subterranean system are different, anatomically they are similar, with both having wavy and fused rays at the outer region of the phloem and a gradual transition between pervious (non-collapsed) and collapsed phloem. Tbe stern and bark periderms have three to seven layers of cells. The bark of younger stern regions is different from the bark of older parts of the stern. Younger stern parts have higher abundance of laticifers in the phloem, and gelatinous fibers arranged in bundles. Compared with the younger regions, older sterns have fewer laticifers and the gelatinous fibers are scattered in the phloem. The root and the xylopodium bark are structurally similar to each other, with a higher abundance of laticifers than sterns. Starch was found in the roots, but not in sterns.

Anatomy of pneumatophore of Mauritia vinifera mart

Pneumatoforos de Mauritia vinifera Mart. foram coletados de plantas com seis meses de idade mantidas submersas em agua com o objetivo de induzir a formacao de pneumatoforos. Peumatoforos com 20 dias de idade possuem uma coifa bastante proeminente na raiz. A epiderme e composta de celulas hexagonais, tangencialmente distribuidas ao longo da superficie cilindrica do orgao. Em secao transversal os pneumatoforos possuem epiderme simples. O cortex e formado por um parenquima esclerificado, um aerenquima com espacos grandes intercelulares e uma endoderme cujas celulas possuem estrias de Caspary. O cilindro vascular e poliarco, com medula e cercado por um periciclo unisseriado. Anatomicamente os pneumatoforos com 4 meses de idade sao semelhantes aos com 20 dias de idade, sendo a unica excecao a ausencia da epiderme nos mais velhos. A epiderme e substituida por um tecido protetor lignificado cujas celulas sao suberizadas e se projetaram fora dando um aspecto filamentoso a esse tecido. Nao foi verificado acumulo de taninos ou amido nos pneumatoforos, com excecao da presenca de estolitos na coifa da raiz. Nao houve formacao de lenticelas nos pneumatoforos de M. vinifera estudados. A principal funcao dos pneumatoforos de M. vinifera e permitir trocas gasosas e ajudar no suprimento de oxigenio as porcoes subemersas da raiz.

Anatomical and biochemical changes in the composition of developing seed coats of annatto (Bixa orellana L.)

Seeds of Bixa orellana (L.) have a sclerified palisade cell layer, which constitutes a natural barrier to water uptake. In fact, newly fully developed B. orellana seeds are highly impermeable to water and thereby dormant. The purpose of this work is to investigate, from a developmental point of view, the histochemical and physical changes in the cell walls of the seed coat that are associated with the water impermeability. Seed coat samples were analyzed by histochemical and polarization microscopy techniques, as well as by fractionation/HPAEC-PAD. For histochemical analysis the tissue samples were fixed, dehydrated, embedded in paraffin and the slides were dewaxed and tested with appropriate stains for different cell wall components. Throughout the development of B. orellana seeds, there was a gradual thickening of the seed coat at the palisade region. This thickening was due to the deposition of cellulose and hemicelluloses in the palisade layer cell walls, which resulted in a highly water impermeable seed coat. The carbohydrate composition of the cell walls changed dramatically at the late developmental stages due to the intense deposition of hemicelluloses. Hemicelluloses were mainly deposited in the outer region of the palisade layer cell walls and altered the birefringent pattern of the walls. Xylans were by far the most abundant hemicellulosic component of the cell walls. Deposition of cellulose and hemicelluloses, especially xylans, could be responsible for the impermeability to water observed in fully developed B. orellana seeds.

Seed structure and initial development of Byrsonima basiloba Juss. (Malpighiaceae)

Byrsonima basiloba Juss. es un arbusto de rapido crecimiento que produce frutos comestibles y jugosos. Esta investigacion estudio la morfologia y anatomia de las semillas y plantas jovenes de este arbusto. Su endocarpio duro contiene una semilla por loculo. La semilla esta compuesta por una testa y un tegumento con un endospermo residual. El embrion es de color marfil, con cotiledones largos circinados, anisofilos, foliaceas con apices inconexos. El eje embrionario es corto, recto, con epicotilo corto y radicula, y con una tapa de raiz rudimentaria, y ocupa una pequena porcion de la semilla. En la plantula es posible diferenciar claramente la protoderma del procambium y del meristema primario. Inmediatamente por encima del promeristema se encuentran el parenquima cortical, la epidermis con pelo, y el cilindro vascular ya parcialmente diferenciado, asi como los vasos del xilema con engrosamiento helicoidal, por lo que se puede concluir que la diferenciacion de los tejidos de esta especie se produce muy temprano. La region de cuello, que se origina del xilopodium en la planta adulta, no muestra ningun cambio en el color, siendo oblicua al eje del vastago. Los cotiledones y eofilos son anfistomaticos. La descripcion anatomica puede ayudar con la identificacion taxonomica de las especies, como tambien proporcionar una guia para el futuro, en cuanto a protocolos de cultivo in vitro.

Cultivo in vitro de Brosimum gaudichaudii Tréc. (Moraceae)

The objective of this research was to evaluate the organogenic potential of internodes, leaf discs and roots of Brosimum gaudichaudii using 12 different combinations of the plant growth regulators 6-benzylaminopurine and naphthalene acetic acid in MS medium (half strength), solid medium (6.5 g agar) and sucrose medium (20 g.L-1). Regardless the hormonal combination tested, we observed the formation of friable calluses (2 - 20 mm wide) in 90% of the internode explants. However, the treatments were not able to induce callus or buds on roots and leaf discs. The anatomical analysis revealed meristemoid formation in the outer and inner regions of the calluses. The results may serve as the basis for further testing of callus induction in this species.