Denise Espellet Klein

Ultrastructure of secretory and senescence phase in colleters of Bathysa gymnocarpa and B. stipulata (Rubiaceae)

(Ultraestrutura da fase secretora e da senescente dos coleteres de Bathysa gymnocarpa e B. stipulata (Rubiaceae)). Coleteres sao estruturas secretoras formadas por um eixo parenquimatico que inclui feixes vasculares, circundado por uma camada de celulas epidermicas secretoras em palicada. Em estudos sobre a estrutura dos coleteres tem sido observada a ultraestrutura das celulas secretoras, mas nao discriminam as fases secretora e senescente. Geralmente, em celulas secretores de mucilagem como os coleteres, o reticulo endoplasmatico e o complexo de Golgi estao envolvidos na producao e no transporte da secrecao. Neste estudo, foram determinadas duas fases baseadas na estrutura dos coleteres de Bathysa gymnocarpa K. Schum. and B. stipulata (Vell.) C. Presl. (Rubiaceae): a fase secretora e a fase senescente. Amostras foram coletadas e processadas utilizando tecnicas usuais de microscopia optica e eletronica. Os coleteres estudados sao constituidos por uma camada epidermica em palicada e um eixo central parenquimatico com tracos vasculares raros. Durante a fase secretora, as celulas epidermicas se apresentam com o citoplasma denso, pequenos vacuolos, reticulo endoplasmatico liso e rugoso evidente e complexo de Golgi proximo a grandes vesiculas. Durante a fase senescente, as celulas epidermicas apresentaram o sistema endomembranar desorganizado. Nenhuma organela intacta ou vesicula foi observada. A parede celular mais externa exibiu camadas similares as observadas durante a fase secretora. A fase senescente e facilmente definida pela morfologia do coleter, mas nao e bem definida em nivel subcelular nas celulas secretoras. Nossa investigacao sugere que a morte celular programada se inicia na fase secretora. Contudo, mais evidencias sao necessarias para avaliar esse fenomeno.

Self-incompatibility in a distylous species of Rubiaceae: is there a single incompatibility response of the morphs?

Heterostyly is a genetically controlled floral polymorphism usually associated with an incompatibility system. This set of features is known to occur in several angiosperm families, but some aspects of its biology has not been well studied. The present study investigates cellular aspects of the pollen–pistil interaction after compatible and incompatible pollinations of Psychotria nuda, to increase our knowledge of heteromorphic self-incompatibility (HetSI). The use of bright field, fluorescence and transmission electron microscopy methods allowed us to demonstrate that pollen tubes behave differently after incompatible and compatible pollinations. Pollen tubes were particularly distinct after incompatible pollinations of L- and S-morph flowers. Relative to compatible pollen tubes, incompatible L-morph tubes had a drastic reduction in cellular contents, but no cell rupture. Incompatible S-morph tubes exhibited dense cytoplasm in apical regions, as well as in other regions, accompanied by a rupture of the apex. These results support the hypothesis that L- and S-morph flowers have different incompatibility mechanisms during HetSI.

Purification and characterization of beta-1, 3-glucanase from the secretion of Simira glaziovii colleters (Rubiaceae)

In this study, b-1,3-glucanase was isolated from Simira glaziovii secretion. The purification process was achieved by a combination of chromatographic methods and was analyzed by SDS-PAGE. The purified enzyme presented an estimated molecular mass of 35 kDa. The optimum pH of enzyme was 5.2

Self-incompatibility in passion fruit: cellular responses in incompatible pollinations

Self-incompatibility (SI) is a genetic mechanism in angiosperms that prevents selfing. The SI system in passion fruit (Passiflora edulis Sims) was investigated using hand pollinations. Pollen tube growth was inspected by microscopy, and sequence analysis of potential regulators of this process was carried out. The results revealed that the pollen tubes grew slowly and were often completely arrested in the stigma in an incompatible combination. Under these circumstances the pollen tube was rapidly and significantly rearranged, followed by the rapid deposition of callose in the stigma during the SI response. The structural changes in the pollen grain after an incompatible pollination were investigated using scanning electron microscopy. Furthermore, ultrastructural observations during incompatible interactions showed that the membrane system of the pollen tube was damaged, and fertilisation was not observed or was considerably delayed when compared to compatible interactions. The analysis presented here provides evidence that the passion fruit genome presents similar sequences to those encoding factors involved in SI in different species. These results suggest that, in the SI system of passion fruit, the rejection of an incompatible pollen grain is characterised by drastic structural changes in both pollen and pollen tube.

Evaluation of soapberry (Sapindus saponaria L.) leaf extract against papaya anthracnose

Chemical fungicides provide the primary means to control fungal infection in fruits and vegetables in the postharvest. Exploitation of natural products to control decay and prolong the storage life of perishables has received more attention. In this study, hydroethanolic extracts from the leaves of soapberry (Sapindus saponaria L.) were investigated for their inhibitory activity against the fungus Colletotrichum gloeosporioides, the causal agent of anthracnose in papaya fruits. To evaluate the antifungal activity of the plant extract, the latter was incorporated into potato-dextrose-agar (PDA) medium at different concentrations (10, 50 and 100 mg mL), and mycelial growth inhibition, spore production inhibition and morphological changes were evaluated at room temperature after 7 days. Efficacy of the extract Marinho, G.J.P.; Klein, D.E.; Siqueira Junior, C.L. Avaliação de extrato foliar de saboeiro (Sapindus saponaria L.) contra anthracnose em frutos de mamoeiro. Summa Phytopathologica, v.44, n.2, p.127-131, 2018. was noted when it was used at 50 mg mL and 100 mg mL, resulting in a reduction in the mycelial growth (P< 0.05). At 50 mg mL, the extract causes morphological changes by reducing the size of hyphae, which become shorter and more branched. At 100 mg mL extract, damages in the hyphal structure were more severe, causing mycelial rupture. In vivo treatment with 100 mg mL extract prevented the development of anthracnose symptoms in fresh papaya fruits. Soapberry leaf extract has strong inhibitory activity against C. gloeosporioides, preventing the mycelial growth and reducing the appearance of anthracnose symptoms. Taken together, these results demonstrated the potential of this extract as a natural fungicide, constituting an alternative measure for disease control in papaya fruits.

Silica bodies in leaves of neotropical Podostemaceae: taxonomic and phylogenetic perspectives

Background and Aims The presence, location and morphology of silica bodies are informative anatomical characters in angiosperms, mainly in Poales. In Podostemaceae, a strictly aquatic family, these structures are mentioned frequently, but there is limited insight into their location and morphological features. In the present study we focused on describing and analysing the morphological diversity of silica bodies in leaves of neotropical Podostemaceae at the intra- and interspecific levels to determine their taxonomic and phylogenetic relevance. Methods We studied 103 specimens distributed across 40 species. Silica body morphological traits were analysed under light and scanning electron microscopy. Additionally, data from three species of Hypericaceae (sister group) were retrieved from the literature. A phylogenetic framework based on four molecular markers was built in order to reconstruct ancestral character states related to silica bodies in neotropical Podostemaceae. Key Results Silica bodies were detected in epidermal, subepidermal and perivascular cells, presenting different shapes and surface morphology. Presence and location were used for primary differentiation while surface morphology and lumen (presence and shape) were used for finer distinctions. Intraspecific comparisons among samples showed that the length and width of these structures were highly variable. Maximum parsimony and maximum likelihood analyses for ancestral character reconstruction were congruent. Three out of five characters showed a statistically strong phylogenetic signal. Conclusions Silica bodies were reported for the first time for 19 taxa, and their morphological diversity is greater than reported in previous studies. Their presence can be considered an apomorphy in Podostemaceae. Although some significant differences were detected in length and width, qualitative characters are more informative at both specific and generic ranks.