Interactive signal transfer in the leaf apoplast between host and pathogen during successful infection
Zusammenfassung der Projektergebnisse
Two main problems were addressed: (1) how does the pathogen avoid defence measures of the host? (2) Does the infection of barley roots wilh Piriformospora spores reprogram barley leaves to induce resistance vs. Blumeria? (1) The first question was approached by measuring the forces (membrane potential; pH-gradient) which drive sugars and amino acids (cotransport). It is shown that - within a test period of 7 days following inoculation - the membrane potential of the barley changes only marginally when infected with Bipolaris conidia, and not at all when infected with Blumeria, a somewhat surprising result. (2) The question whether root inoculation of susceptible barley with P. indica spores would induce resistance against B. graminis was approached by investigating the short- and longterm signaling between root and leaf (external or apoplastic pH). Contact of barley roots (rot hairs) with chlamydospores of P. indica yielded an immediate transient alkalinization, reminiscent of the well-known elicitor response. Interestingly, dead spores gave a similar response. Apoplastic pH, measured in the leaf during and after the inoculation, changed within minutes, however into the acidic direction which indicated a transformation of the signal. In the long term apoplastic pH followed the pattern known from earlier tests (Felle el al 2004): about 20 hours after inoculation with B. graminis apoplastic pH massively increased (up to 2 pH units) in case the roots had been preincubated with P. indica spores several days before. This corroborates our earlier interpretation that this pH increase was an essential resistance facior. Following up this rationale, it indicates that P. indica infection in fact induces resistance in barley against powdery mildew and that this can be followed up by pH signaling.
Projektbezogene Publikationen (Auswahl)
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(2005) Root-to-shoot signalling: apoplastic alkalinization, a general stress response and defence factor in barley. Protoplasma 227: 17-24
Felle HH, Herrmann A, Hückelhoven R, Kogel K-H
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(2008) Interactive signal transfer belween host and pathogen during successful infection of barley leaves by Blumeria graminis and Bipolaris sorokiniana. Journal of Plant Physiology 165: 52-59
Felle HH, Herrmann A, Schäfer P, Hückelhoven R, Kogel, K.-H.
