Browsing by Author "Freitas, Regina"
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- Interactions among grapevine disease-causing fungi. The role of reactive oxygen speciesPublication . Oliveira, Helena; Freitas, Regina; Rego, Cecilia; Ferreira, Ricardo BoavidaBotryosphaeria parva, Eutypa lata and Phomopsis viticola are ascomyceteous fungi responsible for severe canker and dieback in numerous woody plants. In grapevine, these pathogens colonise the wood mainly through pruning wounds, and the diseases gradually develop, leading to partial or total vine death. In the present study, the three fungal species were grown in Czapek Dox modifi ed medium. Under these conditions, fungal colonies are able to distinguish self from non-self. The production of reactive oxygen species (ROS) was analysed by specifi cally staining for superoxide (O2 .-) or peroxide (O2 2-) radicals. The presence of ROS in both isolated cultures and fungal interactions was confi rmed. All fungi produced both radicals, in every interaction. However, the patterns of ROS production depend on the fungus itself and on the fungal species with which it is interacting, being also dependent on the presence of antioxidant compounds in the surrounding medium. It is as though a fungal species hierarchy could be established for every interaction under each set of conditions (i.e. habitat). The results obtained suggest that fungi display more complex behaviours than generally acknowledged. They are able to recognize potential contestants and built up defence reactions, as well as weaken plant defences and structures to induce infection.
- A nontoxic polypeptide oligomer with a fungicide potency under agricultural conditions which is equal or greater than that of their chemical counterpartsPublication . Monteiro, Sara; Carreira, Alexandra; Freitas, Regina; Pinheiro, Ana Margarida; Ferreira, Ricardo BoavidaThere are literally hundreds of polypeptides described in the literature which exhibit fungicide activity. Tens of them have had attempted protection by patent applications but none, as far as we are aware, have found application under real agricultural conditions. The reasons behind may be multiple where the sensitivity to the Sun UV radiation can come in first place. Here we describe a multifunctional glyco-oligomer with 210 kDa which is mainly composed by a 20 kDa polypeptide termed Blad that has been previously shown to be a stable intermediary product of β-conglutin catabolism. This oligomer accumulates exclusively in the cotyledons of Lupinus species, between days 4 and 12 after the onset of germination. Blad-oligomer reveals a plethora of biochemical properties, like lectin and catalytic activities, which are not unusual per si, but are remarkable when found to coexist in the same protein molecule. With this vast range of chemical characteristics, antifungal activity arises almost as a natural consequence. The biological significance and potential technological applications of Blad-oligomer as a plant fungicide to agriculture, its uniqueness stems from being of polypeptidic in nature, and with efficacies which are either equal or greater than the top fungicides currently in the market are addressed
- The unique biosynthetic route from Lupinus Beta-conglutin gene to bladPublication . Monteiro, Sara; Freitas, Regina; Rajasekhar, Baru T.; Teixeira, Artur R.; Ferreira, Ricardo BoavidaBackground: During seed germination, b-conglutin undergoes a major cycle of limited proteolysis in which many of its constituent subunits are processed into a 20 kDa polypeptide termed blad. Blad is the main component of a glycooligomer, accumulating exclusively in the cotyledons of Lupinus species, between days 4 and 12 after the onset of germination. Principal Findings: The sequence of the gene encoding b-conglutin precursor (1791 nucleotides) is reported. This gene, which shares 44 to 57% similarity and 20 to 37% identity with other vicilin-like protein genes, includes several features in common with these globulins, but also specific hallmarks. Most notable is the presence of an ubiquitin interacting motif (UIM), which possibly links the unique catabolic route of b-conglutin to the ubiquitin/proteasome proteolytic pathway. Significance: Blad forms through a unique route from and is a stable intermediary product of its precursor, b-conglutin, the major Lupinus seed storage protein. It is composed of 173 amino acid residues, is encoded by an intron-containing, internal fragment of the gene that codes for b-conglutin precursor (nucleotides 394 to 913) and exhibits an isoelectric point of 9.6 and a molecular mass of 20,404.85 Da. Consistent with its role as a storage protein, blad contains an extremely high proportion of the nitrogen-rich amino acids