Maria Cristina Da Silva

Coffee (Coffea arabica L.) genes early expressed during infection by the rust fungus (Hemileia vastatrix)

SUMMARY The beverage cash crop coffee (Coffea arabica L.) is subject to severe losses caused by the rust fungus Hemileia vastatrix. In naturally resistant coffee plants, a specific hypersensitive reaction (HR) may be elicited early to stop fungal infection. To isolate host genes involved in HR, we undertook an expressed sequence tags (ESTs) analysis. Two cDNA libraries were constructed using suppression subtractive hybridization (SSH) and 527 non-redundant ESTs were generated from 784 randomly picked clones. Classification of the ESTs into several functional categories showed that more than one-quarter of the predicted proteins might encode disease resistance (R) proteins, stress- and defence-proteins, and components of signal transduction pathways. Twenty-eight differentially screened sequences (DSSs) were selected after differential hybridization of 1000 cDNA clones from each library. Investigation of the expression patterns of a subset of 13 DSSs showed higher levels of gene expression in inoculated plants compared with control plants. HR-up-regulation of transcript accumulation occurred for 9 out of the 13 genes 24 and 48 h after H. vastatrix challenge. Two genes encoded homologues of the Arabidopsis DND1 and NDR1 proteins, suggesting conservation of resistance signalling pathways in perennial plants. Other HR-regulated sequences matched receptor kinases, AP2 domain- and WRKY transcription factors, cytochromes P450, heat shock 70 proteins, glucosyltransferases and proteins of unknown function. The ESTs reported here provide a useful resource for studying coffee resistance responses and for improving C. arabica for durable disease resistance.

Four new species of Desmodora (Nematoda) from the deep south-east Atlantic, and a case of intersexuality in Desmodoridae

Four new species of the genus Desmodora are described from the South Atlantic off the south-eastern coast of the State of Rio de Janeiro, Brazil. Desmodora porosum sp. nov. is characterized by sexual dimorphism in the shape of the amphids, which are closed loop-shaped in males, and multispiral amphids in females. A case of intersexuality was found in the species, with a functional female gonad. Desmodora profundum sp. nov. is characterized by filiform spicules with a capitulum, buccal cavity with one dorsal and one small ventral tooth, tail cylindrical with a terminal spinneret, and wider rings in the neck region than on the rest of the body. Desmodora veronicae sp. nov. possesses cryptospiral amphids, a buccal cavity with one dorsal tooth and two smaller ventral teeth, 14 tubular pre-cloacal supplements, two ventral cuticular protruberances on the tail, and curved spicules with a capitulum and velum. Desmodora curvatum sp. nov. has the cuticle finely striated, without somatic setae, multispiral amphids, and a gubernaculum without apophysis, curved dorsally with the tip directed toward the end of the body.

Five new species of Oncholaimellus (Oncholaimidae: Nematoda) from north-east Brazil, with an emended diagnosis and an updated key to the genus

Five new species of Oncholaimellus are described. They were found in macrofauna samples from the continental shelf in the Potiguar Basin, north-east Brazil. Cuticular pores with a sclerotized outline associated with a gland were observed in some species. Oncholaimellus multiporus sp. nov. is differentiated from other species by the presence of cuticular pores of different sizes; the smaller pores are abundant and give an appearance of ornamentation. Oncholaimellus intersexus sp. nov. and O. distortus sp. nov. are similar, but differ in the size of the external labial and cephalic setae compared to the corresponding diameter, the presence of the cuticular pores and the tail shape. Oncholaimellus paulus sp. nov. and O. sineporus sp. nov. are similar, although features such as the external labial and cephalic setae size compared to the corresponding diameter and the cuticular pores differentiate between them.

Isoenzymatic characterization of Colletotrichum kahawae isolates with different levels of aggressiveness

The hemibiotrophic fungus Colletotrichum kahawae is the causal agent of Coffee Berry Disease - CBD, an economically devastating disease restricted to Arabica coffee production in Africa. Understanding pathogen variability is crucial for the implementation of disease control measures. In this study, six isoenzymatic systems (esterase, acid and alkaline phosphatase, malate dehydrogenase, peroxidase and superoxide dismutase) were used to assess the genetic variation among 12 C. kahawae isolates (from different geographic origins and with different levels of aggressiveness towards coffee) and one Colletotrichum gloeosporioides isolate (not pathogenic to green berries). Cluster analysis of the banding profiles obtained for the six enzymes enabled the differentiation of the two species and revealed the existence of intraspecific variability among C. kahawae isolates. Alkaline phosphatase was the most discriminative enzyme, allowing also the discrimination between the most and least aggressive isolates of C. kahawae.

STRUCTURAL EFFECTS OF RADIATION STERILISATION ON SODIUM HYALURONATE

ABSTRACT The molecular weight profiles, reducing and unsaturated carbohydrates in gamma and electron beam (E-beam) irradiated (0-100 kGys) sodium hyaluronate samples (NaHA, in solid form and 1% w/v aqueous solutions), were determined by gel permeation chromatography (GPC), 3,5-dintrosalicylic (DNS) acid assay, and Warren assay, respectively, in order to assess induced degradation, the latter via an anticipated free radical-induced β-elimination mechanism. NaHA was depolymerised by both gamma- and E-beam-irradiation, the extent of depolymerisation being dependent upon irradiation intensity. Gamma-irradiation generally resulted in higher degrees of depolymerisation than E-beam-irradiation, and NaHA solutions were depolymerised to a greater extent than NaHA solids by gamma-irradiation, at the same irradiation levels. Measured reducing sugars correlated with theoretical levels (calculated from determined peak molecular weights, Mp). Measured non-reducing unsaturated glucuronates were lower than measured / theoretical reducing sugars, indicating that not all non-reducing ends created by depolymerisation contained Warren assay active unsaturated sugars.