Journal Article

The Plant Growth-Promoting Fungus <i>Penicillium simplicissimum</i> GP17-2 Induces Resistance in <i>Arabidopsis thaliana</i> by Activation of Multiple Defense Signals

Md. Motaher Hossain, Farjana Sultana, Mayumi Kubota, Hiroyuki Koyama and Mitsuro Hyakumachi

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 48, issue 12, pages 1724-1736
Published in print December 2007 | ISSN: 0032-0781
Published online December 2007 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcm144
The Plant Growth-Promoting Fungus Penicillium simplicissimum GP17-2 Induces Resistance in Arabidopsis thaliana by Activation of Multiple Defense Signals

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  • Biochemistry
  • Molecular and Cell Biology
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Arabidopsis thaliana grown in soil amended with barley grain inocula of Penicillium simplicissimum GP17-2 or receiving root treatment with its culture filtrate (CF) exhibited clear resistance to Pseudomonas syringae pv. tomato DC3000 (Pst). To assess the contribution of different defense pathways, Arabidopsis genotypes implicated in salicylic acid (SA) signaling expressing the NahG transgene or carrying disruption in NPR1 (npr1), jasmonic acid (JA) signaling (jar1) and ethylene (ET) signaling (ein2) were tested. All genotypes screened were protected by GP17-2 or its CF. However, the level of protection was significantly lower in NahG and npr1 plants than it was in similarly treated wild-type plants, indicating that the SA signaling pathway makes a minor contribution to the GP17-2-mediated resistance and is insufficient for a full response. Examination of local and systemic gene expression revealed that GP17-2 and its CF modulate the expression of genes involved in both the SA and JA/ET signaling pathways. Subsequent challenge of GP17-2-colonized plants with Pst was accompanied by direct activation of SA-inducible PR-2 and PR-5 genes as well as potentiated expression of the JA-inducible Vsp gene. In contrast, CF-treated plants infected with Pst exhibited elevated expression of most defense-related genes (PR-1, PR-2, PR-5, PDF1.2 and Hel) studied. Moreover, an initial elevation of SA responses was followed by late induction of JA responses during Pst infection of induced systemic resistance (ISR)-expressing plants. In conclusion, we hypothesize the involvement of multiple defense mechanisms leading to an ISR of Arabidopsis by GP17-2.

Keywords: Barley grain inoculum; Culture filtrate; Ethylene; Jasmonate; Pseudomonas syringae pv. tomato DC3000; Salicylic acid

Journal Article.  8919 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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