Sucrose-mediated priming of plant defense responses and broad-spectrum disease resistance by overexpression of the maize pathogenesis-related PRms protein in rice plants

11 pages, 6 figures.-- PMID: 17601170 [PubMed].Expression of pathogenesis-related (PR) genes is part of the plant's natural defense response against pathogen attack. The PRms gene encodes a fungal-inducible PR protein from maize. Here, we demonstrate that expression of PRms in transgenic rice confers broad-spectrum protection against pathogens, including fungal (Magnaporthe oryzae, Fusarium verticillioides, and Helminthosporium oryzae) and bacterial (Erwinia chrysanthemi) pathogens. The PRms-mediated disease resistance in rice plants is associated with an enhanced capacity to express and activate the natural plant defense mechanisms. Thus, PRms rice plants display a basal level of expression of endogenous defense genes in the absence of the pathogen. PRms plants also exhibit stronger and quicker defense responses during pathogen infection. We also have found that sucrose accumulates at higher levels in leaves of PRms plants. Sucrose responsiveness of rice defense genes correlates with the pathogen-responsive priming of their expression in PRms rice plants. Moreover, pretreatment of rice plants with sucrose enhances resistance to M. oryzae infection. Together, these results support a sucrose-mediated priming of defense responses in PRms rice plants which results in broad-spectrum disease resistance.This work was supported by grants from the Ministerio de Ciencia y Tecnología, BIO2003-04936-C02-01 and BIO2006-05583 to B. San Segundo, and BIO2003-04936-C02-02 to J. Messeguer.Peer reviewe

Pathogen-induced production of the antifungal AFP protein from Aspergillus giganteus confers resistance to the blast fungus Magnaporthe grisea in transgenic rice

13 pages, 7 figures.-- PMID: 16167766 [PubMed].Rice blast, caused by Magnaporthe grisea, is the most important fungal disease of cultivated rice worldwide. We have developed a strategy for creating disease resistance to M. grisea whereby pathogen-induced expression of the afp (antifungal protein) gene from Aspergillus giganteus occurs in transgenic rice plants. Here, we evaluated the activity of the promoters from three maize pathogenesis-related (PR) genes, ZmPR4, mpi, and PRms, in transgenic rice. Chimeric gene fusions were prepared between the maize promoters and the β-glucuronidase reporter gene (gus A). Histochemical assays of GUS activity in transgenic rice revealed that the ZmPR4 promoter is strongly induced in response to fungal infection, treatment with fungal elicitors, and mechanical wounding. The ZmPR4 promoter is not active in the seed endosperm. The mpi promoter also proved responsiveness to fungal infection and wounding but not to treatment with elicitors. In contrast, no activity of the PRms promoter in leaves of transgenic rice was observed. Transgenic plants expressing the afp gene under the control of the ZmPR4 promoter were generated. Transformants showed resistance to M. grisea at various levels. Our results suggest that pathogen-inducible expression of the afp gene in rice plants may be a practical way for protection against the blast fungus.This research was supported by the European Commission (QLRT-CT99-1484, EURICE) and by the Ministerio de Ciencia y Tecnologia (BIO2003-04936-C02). The mpi:gus rice plants were generated in the framework of the ERRI (Engineering Rice for Resistance to Insects) project from the European Commission (FAIR-CT97-3761).Peer reviewe