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- In vitro and in vivo quantification of elicitin expression in Phytophthora cinnamomiPublication . Horta, Marília; Sousa, Nelson; Coelho, A. C.; Neves, D.; Cravador, A.The differential expression of four Phytophthora cinnamomi elicitin genes was analysed by Real Time RT-PCR. In in vitro cultures, the a-cinnamomin gene showed the highest level of expression, the b-cinnamomin gene (b-cin) was the most inducible, and the HAE transcripts were in low abundance. Transcription of all the elicitins was active during the active growth of the pathogen when infecting cork oak (Quercus suber) roots, and as host colonization progressed, the level of b-cin expression fell, while that of a-cin rose. In an antisense transgenic strain, the silencing of b-cin also negatively affected the expression of other elicitin genes in the cluster. The reduced in planta growth of the b-cin knock-out is related to the altered pattern of elicitin gene expression, supporting the idea that one of the functions of elicitins is related, directly or indirectly, with pathogenesis.
- Involvement of the beta-cinnamomin elicitin in infection and colonisation of cork oak roots by Phytophthora cinnamomiPublication . Cravador, A.; Horta, Marília; Caetano, P.; Medeira, C.; Maia, I.The virulence of two wild type (PA45 and PA37) and two genetically modified (13C: hygromycin resistant; FATSS: hygromycin resistant and β-cin knock-down) Phytophthora cinnamomi strains towards cork oak (Quercus suber) was assessed via a quantitative evaluation of disease symptoms arising from a soil infestation assay, and by a istological analysis of root colonization. Comparison of virulence, as expressed by symptom severity, resulted in the following ranking: highly virulent (wild type strains), medium virulence (strain 13C) and weakly virulent (FATSS). Both transgenic strains were compromised in their virulence, as expressed by symptom severity, but strain 13C was much less affected than FATSS. Microscopic observation showed that the FATSS strain was unable to effectively invade the root, while 13C and the two wild type strains were all able to rapidly colonize the whole root, including the vascular tissue. These results strengthen the notion that elicitins are associated, either directly or indirectly, with the infection process of Phytophthora.