The moss Physcomitrella patens is a suitable model plant to analyze the activation of defense mechanisms after pathogen assault. In this study, we show that Colletotrichum gloeosporioides isolated from symptomatic citrus fruit infects P. patens and cause disease symptoms evidenced by browning and maceration of tissues. After C. gloeosporioides infection, P. patens reinforces the cell wall by the incorporation of phenolic compounds and induces the expression of a Dirigent-protein-like encoding gene that could lead to the formation of lignin-like polymers. C. gloeosporioides-inoculated protonemal cells show cytoplasmic collapse, browning of chloroplasts and modifications of the cell wall. Chloroplasts relocate in cells of infected tissues toward the initially infected C. gloeosporioides cells. P. patens also induces the expression of the defense genes PAL and CHS after fungal colonization. P. patens reporter lines harboring the auxin-inducible promoter from soybean (GmGH3) fused to β-glucuronidase revealed an auxin response in protonemal tissues, cauloids and leaves of C. gloeosporioides-infected moss tissues, indicating the activation of auxin signaling. Thus, P. patens is an interesting plant to gain insight into defense mechanisms that have evolved in primitive land plants to cope with microbial pathogens.
The most severe form of citrus canker disease is caused by Xanthomonas axonopodis pv. citri (Xac) and affects all types of important citrus crops, reducing fruit yield and quality. Copper-based products are routinely used as a standard control measure for citrus canker. In this work we demonstrate that copper treatment induces the viable but nonculturable (VBNC) state in Xac but does not prevent the development of symptoms in susceptible plants. Short-term exposures to different concentrations of copper solutions were assayed to determine which treatment resulted in Xac nonculturability. Treatment of 10(6) mL(-1) Xac cells for 10 min in a 135-muM CuSO(4) solution (equivalent to three times the free soluble copper concentration applied in one field treatment) resulted in nonculturability. However, 16% of cells were viable based on 5-cyano-2,3-ditolyl tetrazolium chloride staining and 1% were capable of producing canker lesions after infiltrating grapefruit plants. If induction of the VBNC state in Xac cells were to occur under field conditions, this would have to be taken into consideration for an effective control of canker disease.
Xanthomonas axonopodis pv. citri (Xac) produce cancro cítrico en todas las especies cítricas comerciales. La bacteria puede diseminarse mediante material vegetal de propagación contaminado y asintomático. Con el objetivo de optimizar técnicas de detección de bacterias para el análisis de rutina de material vegetal cítrico asintomático, se compararon las técnicas ELISA, Inmunoflorescencia, PCR, qRT_PCR e inoculación en plantas indicadoras (bioensayo). Las pruebas se realizaron a partir de diluciones al décimo entre 108 ufc.mL-1 y 102 ufc.mL-1 de un cultivo puro de cepa 49b. El nivel de detección obtenido fue de 1,8 x 102 ufc. mL-1 utilizando inmunoflorescencia, 1,8x104 ufc.mL-1 con ELISA indirecto, 1,8x103 ufc. mL-1 mediante la técnica de PCR, 10 ufc. mL-1 a través de qRT_PCR, y 230 ufc.mL -1 en plantas inoculadas de naranjo amargo. En base a estos resultados y teniendo en cuenta que para el análisis masivo de muestras es importante además de la sensibilidad, el costo y la practicidad, las técnicas de PCR e inoculación en plantas hospedero fueron las que reunieron las mejores características para ser evaluadas en material vegetal asintomático.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.