RESUMO
BACKGROUND: Rice sheath blight (caused by Rhizoctonia solani) and tobacco mosaic virus are very important plant diseases, causing a huge loss in global crop production. Paenibacillus kribbensis PS04 is a broad-spectrum biocontrol agent, used for controlling these diseases. Previously, extracellular polysaccharides (EPS) from P. kribbensis PS04 had been purified and their structure was inferred to be fructosan. This study aimed to evaluate the effects of exogenous EPS treatment on plantpathogen interactions. RESULTS: Plant defense genes such as phenylalanine ammonia-lyase, catalase, chitinase, allene oxide synthase, and PR1a proteins were significantly induced by exogenous EPS treatment. Moreover, subsequent challenge of EPSpretreated plants with the pathogens (R. solani or tobacco mosaic virus) resulted in higher expression of defenseassociated genes. Increased activities of defense-associated enzymes, total phenols, and flavonoids were also observed in EPS pretreated plants. The contents of malondialdehyde in plants, which act as indicator of lipid peroxidation, were reduced by EPS treatment. CONCLUSIONS: This study comprehensively showed that EPS produced from P. kribbensis PS04 enhances disease resistance in plants by the activation of defense-associated genes as well as through the enhancement of activities of defense-related enzymes.
Assuntos
Doenças das Plantas/imunologia , Rhizoctonia/patogenicidade , Vírus do Mosaico do Tabaco/patogenicidade , Paenibacillus/imunologia , Doenças das Plantas/microbiologia , Polissacarídeos Bacterianos , Controle Biológico de Vetores , Interações Hospedeiro-Patógeno , Paenibacillus/genética , Resistência à Doença/genética , Reação em Cadeia da Polimerase em Tempo Real , Frutose/análogos & derivadosRESUMO
Electron microscopic studies of mesophyll cells of Nicotiana tabacum leaf systemically infected with-an Egyptian strain of tobacco virus revealed several ultrastructural changes. Chloroplasts were spherical in shape; grana, intergrana lamellae [thylakoid] and chloroplast envelope were broken and peripheral reticulum appeared. Virus infection induced an increase in the number of osmiophilic globules, mitochondria and microbodies. Cristae of mitochondria were lost and mitochondrial envelope was disintegrated. There was an increase in crytal-containing microbodies. Virus particles occured in cytoplasm which also showed vacuolation