Lisete Chamma Davide

Conidial anastomosis tubes in Colletotrichum

We describe the occurrence of special kinds of hyphae that create anastomoses directly between conidia. They can be found both in the laboratory and on infected plants. They first appear within asexual fruiting bodies approximately 15 days after conidiation has begun leading to the appearance of chains of connected conidia. Coincident with this we demonstrate in Colletotrichum lindemuthianum nuclear dynamics, including fragmentation, with cytoplasmic flow and passage of nuclei and organelles between conidia through the anastomosis tubes. We propose that conidial anastomosis tubes play an important role in the life cycle of these fungi.

Conidial anastomosis fusion between Colletotrichum species

Colletotrichum lindemuthianum is a pathogen of the common bean plant (Phaseolus vulgaris) causing anthracnose. Large numbers of isolates can rapidly arise with different genetic and chromosomal compositions but their origin is unknown since sexual fruit bodies have only been found in the laboratory. We have recently described the occurrence of special kinds of hyphae that create anastomoses directly between conidia. In this work we show that conidial anastomoses can occur between two different Colletotrichum species. The implications of this observation on the generation of genetic diversity in these species are discussed.

The effect of cyanide compounds, fluorides, aluminum, and inorganic oxides present in spent pot liner on germination and root tip cells of Lactuca sativa

SPL (spent pot liner) is a solid waste produced by the aluminum industry. This waste has a highly variable composition, consisting of cyanides, fluorides, organics, and metals. The aim of this work was to study the effect of SPL on root tips of Lactuca sativa using current plant bioassays. We observed a decrease in the germination rate with increasing concentrations of SPL. In addition, SPL was found to reduce root growth, which is correlated with a decrease in the mitotic index. Nevertheless, we noticed a significant enhancement in the percentage of stickiness, c-metaphase, anaphase bridges, and laggard chromosomes in dividing cells and also an increase in the number of cells with condensed nuclei. Moreover, SPL was found to alter the root tip surface, resulting in a reduction in the amount of root hair. These results demonstrate that SPL is a toxic agent that leads to cell damage and disturbance.

Cytogenetic alterations induced by SPL (spent potliners) in meristematic cells of plant bioassays.

Spent potliners (SPL) is solid waste generated by the aluminum industry during the manufacture of aluminum metal. Information on the cytotoxicity effect of SPL is necessary to facilitate understanding of their action on organisms and to subsidize environmentally correct solutions. Thus, the aim of the present investigation is to compare the effect of SPL on meristematic cells of Allium cepa and Zea mays and also to discuss the mechanisms of SPL cytotoxicity involved. A strong inhibition on root growth in higher SPL concentrations has been observed in both A. cepa and Z. mays. For cytogenetic analysis, the results showed a reduction of mitotic index and increase of different abnormalities as the SPL concentration increased. We observed bridges, chromosome fragments, stickiness, multipolar anaphase, later segregation and cell death. In general, it was possible to observe an increase of different abnormalities as the SPL concentration increased. It is obvious from the results of the present investigation that SPL is cytotoxic on meristematic cells of plant tests (A. cepa and Z. mays).

Cytogenetics of Pennisetum purpureum Schumack x Pennisetum glaucum L. hybrids and their parents

Foram realizados estudos citogeneticos em quinze acessos do Banco de Germoplasma Forrageiro, da Embrapa Gado de Leite, sendo cinco hibridos interespecificos de Pennisetum purpureum e Pennisetum glaucum e seus genitores. As analises citogeneticas mitoticas realizadas mediante coloracao com reativo de Schiff confirmaram o numero cromossomico de 2n =14, 28 e 21 para os acessos de P. glaucum, P. purpureum e hibridos, respectivamente. Para cada um desses acessos, foram realizadas descricoes do complemento cromossomico e idiogramas, as quais possibilitaram estabelecer relacoes cariotipicas entre os hibridos e seus genitores. Com base nos dados de comprimento total do cromossomo, foi estabelecida a classificacao do cariotipo dos acessos com relacao a simetria. Os cariotipos dos acessos de P. glaucum foram considerados simetricos, ao passo que os hibridos apresentaram cariotipos assimetricos. Para P. purpureum, dois acessos (BAGs 63 e 75) mostraram cariotipos simetricos e tres (BAGs 54, 65 e 91) assimetricos. Nos hibridos interespecificos entre P. purpureum e P. glaucum, foi possivel inferir a procedencia de alguns cromossomos parentais com base nas medidas de comprimento total do cromossomo, presenca de satelite e morfologia do cromossomo.

Cytotaxonomy of some species and of interspecific hybrids of Pennisetum (Poaceae, Poales)

Cytotaxonomic studies were carried out on 26 accessions of Pennisetum spp. originating from the Active Germplasm Bank of Embrapa Gado de Leite-Juiz de Fora, Minas Gerais, Brazil.This study presents cytogenetics and reproductive morphological data for each one of these accessions, which allowed groupings and suggest botanical identifications to be established. The metaphases of the accessions characterized as P. purpureum confirmed the presence of 2n = 28 chromosomes that have already been described for this species. For the hybrids between P. purpureum and P. glaucum and for the hexaploids, resulting from the chromosome duplication of these hybrids, 2n = 21 and 2n = 42 chromosomes were confirmed, respectively. The wild accession identified as P. setosum showed metaphases with 2n = 54 chromosomes, while those characterized as P. nervosum had cells with 2n = 36 chromosomes. The wild accession 15 was different from the others for the morphological characters, with 2n = 36 chromosomes, and was classified as P. orientale. Two statistical procedures were used (canonical variables and cluster analysis on the basis of the Mahalanobis distance), and the results confirmed the conclusions obtained from the cytogenetic and morphologic analysis.

Spent Pot Liner (SPL) induced DNA damage and nuclear alterations in root tip cells of Allium cepa as a consequence of programmed cell death

There are various toxic effects of environmental pollutants, including apoptosis and carcinogenesis. Spent Pot Liner (SPL) is solid waste from the aluminum industry. It has a highly variable composition, including cyanide, fluoride, organics and metals. Preliminary characterizations of the effect of SPL on Allium cepa show the presence of condensed nuclei. Thus, the aim of this study was to analyze the toxic effect of SPL in A. cepa root meristem in the context of programmed cell death (PCD). A lot of specific features of this process such as DNA fragmentation, condensed chromatin, spherical nuclei and the formation of apoptotic-like bodies were observed in root meristem after SPL treatment. Root meristem treated with SPL 25% solution exhibited an alteration in antioxidant enzyme activities; a reduction in NCR as a consequence of high percentage of condensed nuclei; DNA fragmentation, detected by electrophoresis and TUNEL assay; cytoplasm vacuolization and also a disturbance in root morphology. These features are associated with programmed cell death (PCD) under abiotic stress. Therefore, these data show that SPL induces apoptosis-like PCD in root meristem cells of A. cepa.

Effects of sorghum (sorghum bicolor L.) root exudates on the cell cycle of the bean plant (phaseolus vulgaris L.) root

Foram instalados experimentos em casa de vegetacao da Empresa Agropecuaria de MG (EPAMIG) e laboratorio da Universidade Federal de Lavras (UFLA) em 1994, com o objetivo de testar a acao alelopatica de exsudados de raiz de sorgo (sorgoleone - SGL), variedade BR-601, sobre plantas jovens do feijoeiro, variedade Carioca MG. Sorgoleone foi extraido das raizes de sorgo 7 dias apos a semeadura em placas de Petri. Solucoes de 0,01, 0,05, 0,10 e 0,15 mM de SGL foram preparadas usando solucao de Johanson como solvente. Plantas de feijao com 7 dias de idade, germinadas em vermiculita, em casa de vegetacao, foram transplantadas para estas solucoes. O feijoeiro nao mostrou sinais de fitotoxicidade durante o periodo de tratamento; porem, observacoes citogeneticas mostraram que concentracoes de 0,01 mM e acima reduziram o numero de celulas nas fases de profase, metafase e anafase em relacao a testemunha. Entre as celulas em metafase, observaram-se metafases colchicinicas. As percentagens de metafases colchicinicas no 3o e 5o dias apos o transplante variaram com as concentracoes de SGL; no 7o dia, estes valores foram inversamente proporcionais as concentracoes, variando de 34,3% para 0,01 mM a 6,6% para 0,15 mM de SGL. Pode-se observar ainda nas celulas em anafase e telofase cromossomos formando pontes e atrasados, bem como a ocorrencia de metafases poliploides.

Cytotoxic and phytotoxic effects of the main chemical components of spent pot-liner: A comparative approach

Spent pot-liner (SPL) is a hazardous solid waste produced by the aluminum industry. Although its composition may vary, fluoride and cyanide salts as well as aluminum are predominant components. A seed-germination and root-elongation test was performed with Lactuca sativa seeds as a test system. SPL induced decrease of seed germination rate and root elongation. The concentration of 26.5g/L SPL was established from a regression curve as the IC50 (inhibition concentration 50%). Through chemical analyses, the concentrations of fluoride, cyanide and aluminum in SPL solutions of 26.5g/L (IC50), 39.75g/L (1.5IC50) and 13.25g/L (0.5IC50) were determined. Further, a cell-cycle test was conducted with root tips of L. sativa exposed to these same SPL solutions. All test chemicals presented toxic effects on meristematic cells of L. sativa. Aluminum was identified as the SPL component mainly responsible for reduction of the mitotic index. Chromosomal alterations resulted from the interactions among the three main chemical components of SPL, without a clear predominantly responsible agent. Induction of condensed nuclei was mainly due to effects of aluminum and fluoride, and may serve as an indicator of induced cell death.

Effects of Spent Pot Liner on mitotic activity and nuclear DNA content in meristematic cells of Allium cepa.

Industrial waste usually contains complex mixtures of mutagenic chemicals. Spent Pot Liner (SPL) is a complex solid waste from the aluminum industry, which is composed of organics, fluoride salts, inorganic cyanides, metals, and sodium. Due to the toxicity of these compounds, this study sought to use cytogenetics and flow cytometry to assess the effects of SPL on cell cycle parameters and DNA content in meristematic cells of Allium cepa. Three concentrations of leachates from SPL-soil mixtures were used for the study: 0, 10, and 25%. Roots were collected and analyzed after 4, 8, 12, 24, and 36 h of exposure to the above SPL leachates. The results showed an overall mitodepressive effect accompanied by an increased percentage of condensed nuclei and genomic instability as evidenced by the presence of cellular/chromosomal abnormalities. Terminal deoxynucleotidyl transferase dUTP nick end labeling revealed nuclei with fragmented DNA, a marker of programmed cell death. This study also addressed the question of reversibility of the effects of SPL and found that 36 h of exposure to 25% SPL seemed to be the point at which the effects on the induction of apoptosis became irreversible.