Browsing by Author "Costa, A."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Citrus tristeza virus p23 may suppress systemic silencing but is not related to the kind of viral syndromePublication . Costa, A.; Marques, N T.; Nolasco, GustavoCitrus tristeza virus (CTV) the causal agent of the most devastating viral disease of citrus, has evolved three silencing suppressor proteins namely p20, p23 and p25 protein, previously reported for the monophyletic isolate T36. In this study the p23 suppressing activity from isolates of each of seven phylogenetic groups recognized for CTV was characterized in Nicotiana benthamiana 16C plants expressing GFP. Data revealed that the p23 protein from each phylogenetic group was able to transiently suppress the local but not the short-range silencing. p23 from Group 5 was the most efficient local suppressor followed by Groups 1, 3a, 3b and 4; the Groups 2 and M were less efficient. Different development of systemic silencing was observed among p23 proteins. This was most conspicuous for Gp 5, which completely blocked the GFP systemic silencing, suggesting that a quantitative relationship might exist between local and systemic silencing. A 3D model of the p23 protein was constructed showing differences within the Zn-finger region, which, however, do not totally explain the differences found. It was not possible to trace a relationship between the syndromes tribute to the various phylogenetic groups and p23 activity. (C) 2014 Elsevier Ltd. All rights reserved.
- Identification of an RNA silencing suppressor encoded by Grapevine leafroll-associated virus 3Publication . Gouveia, P.; Dandlen, S. A.; Costa, A.; Marques, N T.; Nolasco, GustavoGLRaV-3, a member of the Closteroviridae family and type member of the genus Ampelovirus, is involved in the grapevine leafroll disease. Until now no RNA silencing suppressor has been found among viruses of this genus, contrary to what happens with a large number of other viral genera. In the sister genus Closterovirus, RNA silencing suppressors are present in the 3' end of the genome and have molecular weights close to 20 KDa. To test for RNA suppressing activity screening of p21, p19.6 and p19.7 proteins, coded for in an analogous genomic location of the GLRaV-3 was undertaken. Only p19.7 revealed suppressor activity demonstrated in diverse silencing inducing systems. This suppressor is able to overcome strong silencing inducers and shares several properties with the BYV p21-like family of suppressors of the closteroviruses. This is the first report of an RNA silencing suppressor in the genus Ampelovirus.
- Inter-annual variations of macrobenthic communities over three decades in a land-locked coastal lagoon (Santo André, SW Portugal)Publication . Correia, M. J.; Costa, J. L.; Chainho, P.; Félix, P. M.; Chaves, M. L.; Medeiros, J. P.; Silva, G.; Azeda, C.; Tavares, P.; Costa, A.; Costa, A. M.; Bernardo, J.; Cabral, H. N.; Costa, M. J.; Cancela, M. LeonorSanto Andre is an enclosed brackish water coastal lagoon with temporary connections to the sea by a man-made channel. The exchange and mixture of saltwater and freshwater is irregular and the lagoon may show daily and seasonal fluctuations, but also long-term variation. Different benthic communities may be present along the annual cycle according to the magnitude of episodic freshwater and sea water inputs. In the last 30 years the communication with the sea has followed different regimes from year to year and, as a consequence, macrobenthic communities, assessed several times during the period before the opening to the sea, shifted from freshwater to marine affinities. Major differences were found between 1979 and 2010, with a preponderance of species with marine affinity, and the 1980s in which the organisms with freshwater affinity prevailed. Benthic communities are frequently used to assess aquatic environmental condition. Metrics used in the indices currently under discussion to assess ecological status of aquatic ecosystems within the scope of European Water Framework Directive were applied to Santo Andre data and the applicability of these metrics to assess quality in this coastal land-locked lagoon was discussed. (C) 2012 Elsevier Ltd. All rights reserved.
- Proton binding properties of humic substances originating from natural and contaminated materialsPublication . Van Zomeren, A.; Costa, A.; Pinheiro, J. P.; Comans, R. N. J.Humic substances (HS) are ubiquitous organic constituents in soil and water and can strongly adsorb metal contaminants in natural and waste environments. Therefore, understanding and modeling contaminant-HS interactions is a key issue in environmental risk assessment. Current binding models for HS, such as the nonideal competitive adsorption (NICA)-Donnan model, are developed and calibrated against natural organic matter from soils and surface waters. The aim of this study is to analyze the proton binding properties of humic and fulvic acidsamplesoriginatingfromsecondarymaterials,wastematerials and natural samples in order to assess whether the charge development of these HS can be described with generic NICA-Donnan parameters. New proton binding parameters are presented for HS isolated from several natural and contaminated (waste) materials. These parameters are shown tobesimilar to those ofHSoriginating from natural environments, suggesting that the NICA-Donnan model and generic binding parameters are adequate to describe proton binding to HS in both natural and contaminated materials. These findings widen the range of environments to which the NICA-Donnan model can be applied and justify its use in geochemical speciation modeling of metal mobility in contaminated (waste) materials.