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- Exposition of cork oak roots to cryptogein reduced the Infection by Phytophtora cinnamomiPublication . Maia, I.; Medeira, C.; Candeias, I.; Moreira, A. C.; Melo, Eduardo P.; Cravador, A.The oomycete P. cinnamomi has been described as strong contributing factor to the decline of cork oak and holm oak stands occurring in the Iberian Peninsula. There are no eradication methods available against this pathogen.
- Cryptogein and capsicein promote defence responses in Quercus suber against Phytophthora cinnamomi infectionPublication . Medeira, C.; Quartin, V.; Maia, I.; Diniz, I.; Matos, M.; Semedo, J.; Scotti Campos, P.; Ramalho, J. C.; Pais, Isabel P.; Ramos, P.; Melo, Eduardo P.; Leitao, A.; Cravador, A.The decline of cork oak (Quercus suber) stands in Iberian Peninsula is associated with infection by Phytophthora cinnamomi. Most Phytophthora species secrete elicitins, which can enhance defence reactions against some pathogens. Here cytological and physiological effects of the elicitins cryptogein and capsicein on cork oak root infection by P. cinnamomi were evaluated. The progression of the pathogen in root tissue and its effects on total fatty acid (TFA) composition of roots and leaves were analysed in seedlings. Net photosynthesis (P (n) ), stomatal conductance (g (s) ), chlorophyll a fluorescence measurements (quantum yield of linear electron transport I center dot (e) , photochemical quenching q (P,) non-photochemical quenching NPQ) and carotenoid determinations were carried out in well established (4 months) plants. In elicitin-treated roots, 2 days after inoculation, the pathogen which presented loss of viability and membrane degradation was mainly restricted to the intercellular spaces of the cortical parenchyma, and did not reach the vascular cylinder. Electron dense materials accumulated in the intercellular spaces of the cortex next to disorganized hyphae, suggested to be related with defence reactions. Cryptogein (or its interaction with P. cinnamomi) induced enhanced lipid synthesis in leaves, which may contribute to preserve membrane stability. P. cinnamomi decreased P (n) , g (s) , I center dot (e) , and q (P), whereas elicitin-treated plants displayed values similar to controls. Overall, the results indicated a resistance response of cork oak against this oomycete, induced by the elicitins.
- Quercus suber infected by Phytophthora cinnamomi: effects at cellular level of cinnamomin on roots, stem and leavesPublication . Maia, I.; Medeira, C.; Melo, Eduardo P.; Cravador, A.Phytophthora cinnamomi has been reported to be regularly associated with cork and holm oak decline. This oomycete secretes elicitins, a group of unique highly conserved pr oteins that can enhance plant defence reactions.
- A utilização de elicitinas no combate contra Phytophthora cinnamomi na doença da tinta do castanheiro e no declínio do montadoPublication . Cravador, A.; Medeira, C.; Maia, I.; Moreira, A. C.; Candeias, I.; Melo, Eduardo P.; Sousa, NelsonPhytophthora cinnamomi e P. cambivora são considerados os agentes patogénicos da doença da tinta do castanheiro. Estes agentes invadem e destroem o sistema radicular, levando à morte das árvores e a importantes perdas económicas. O declínio do montado tem sido associado a vários agentes patogénicos, pragas e factores abióticos. Phytophthora cinnamomi tem sido referido como um potencial agente patogénico do sobreiro e azinheira. O aparecimento de mais estirpes de microrganismos patogénicos resistentes a pesticidas impõe o desenvolvimento de novas estratégias de biocontrolo, entre as quais a estimulação de reações de defesa. As elicitinas são proteínas de baixo peso molecular, secretadas por algumas espécies de oomycetes (Phytophthora e Pythium) que induzem reações de hipersensibilidade e aquisição de resistência sistémica nas plantas, contra um grande número de bactérias e fungos patogénicos. Este trabalho é uma síntese dos resultados sobre o efeito da aplicação radicular de várias elicitinas, na infeção do sobreiro, azinheira e castanheiro por P. cinnamomi. A avaliação foi efetuada por observação microscópica dos tecidos invadidos, em especial dos tecidos vasculares. Observou‑se a indução de reações de defesa contra P. cinnamomi quando se submeteram as raízes destas três espécies a pré‑tratamento com as elicitinas criptogeína, capsiceína ou cinamomina. A infeção ficou restrita aos tecidos corticais da raiz, onde o agente patogénico se desorganizou e não progrediu para os vasos, estando associado à acumulação de materiais que se presume serem tóxicos, produzidos nas células dos hospedeiros, em contato com as hifas em desorganização. Os ensaios laboratoriais indicaram que as elicitinas testadas se revelaram muito eficientes no biocontrolo de P. cinnamomi. Será de grande importância desenvolver tecnologia no sentido de obtenção de elicitinas a baixo custo e de criar sistemas eficientes da sua dispersão nas plantas.
- Alpha cinnamomin elicits a defence response against Phytophthora cinnamomi in Castanea sativaPublication . Medeira, C.; Maia, I.; Ribeiro, C.; Candeias, I.; Melo, Eduardo P.; Sousa, N.; Cravador, A.Phytophthora cinnamomi and P. cambivora are considered as the causal agents of Castanea sativa ink disease. These soil-borne plant pathogens invade and destroy the root system leading to the death of the trees. Most Phytophthora species secrete elicitins, a group of unique highly conserved proteins that are able to enhance plant defence responses in a systemic acquired resistance manner against infection by several pathogens. A cluster of four elicitin genes was identified in P. cinnamomi. In previous works one of these elicitins, α- cinnamomin was shown to restrict the invasion of root cortical tissues by P. cinnamomi preventing vascular colonization in cork and holm oak. In the present work, roots of chestnut plantlets grown in vitro were allowed to absorb α-cinnamomin at 100 μg/ml for two days before being inoculated with P. cinnamomi. The effects of this elicitin on host-pathogen interaction were studied at histological and ultrastructural levels. P. cinnamomi was restricted to the outer cortex of 65% of the roots pre-treated with α-cinnamomin. In these roots, the vascular cylinders were free of pathogen. On the contrary, the pathogen reached the vascular cylinder, penetrating the phloem and xylem vessels in all non-treated assayed roots. The signs of pathogen degradation in the cortical parenchyma, mainly in the intercellular spaces, and the increase of a physical barrier in epidermal and sub-epidermal cell wall-media lamella and intercellular spaces by impregnation with phenol-like compounds strongly suggest that α-cinnamomin induced in chestnut defence reactions against P. cinnamomi.
- Crystal structures of the free and sterol-bound forms of beta-cinnamominPublication . Rodrigues, Maria Luisa; Archer, Margarida; Martel, Paulo; Miranda, Sandra; Thomaz, Mónica; Enguita, Francisco J.; Baptista, Ricardo P.; Melo, Eduardo P.; Sousa, Nelson; Cravador, A.; Carrondo, Maria A.The crystal structure of the elicitin h-cinnamomin (h-CIN) was determined in complex with ergosterol at 1.1 A° resolution. h-CIN/ergosterol complex crystallized in the monoclinic space group P21, with unit cell parameters of a =31.0, b =62.8, c =50.0 A° and b =93.4- and two molecules in the asymmetric unit. Ligand extraction with chloroform followed by crystallographic analysis yielded a 1.35 A° structure of h-CIN (P43212 space group) where the characteristic elicitin fold was kept. After incubation with cholesterol, a new complex structure was obtained, showing that the protein retains, after the extraction procedure, its ability to complex sterols. The necrotic effect of h-CIN on tobacco was also shown to remain unchanged. Theoretical docking studies of the triterpene lupeol to h-CIN provided an explanation for the apparent inability of h-CIN to bind this ligand, as observed experimentally. D 2005 Elsevier B.V. All rights reserved.