Alternaria Brassicae Induces Systemic Jasmonate Responses in Arabidopsis Which Travel to Neighboring Plants via a Piriformsopora Indica Hyphal Network and Activate Abscisic Acid Responses

Abstract

Stress information received by a particular local plant tissue is transferred to other tissues and neighboring plants, but how the information travels is not well understood. Application of <i>Alternaria Brassicae</i> spores to Arabidopsis leaves or roots stimulates local accumulation of jasmonic acid (JA), the expression of JA-responsive genes, as well as of <i>NITRATE TRANSPORTER</i> (<i>NRT</i>)<i>2.5</i> and <i>REDOX RESPONSIVE TRANSCRIPTION FACTOR1</i> (<i>RRTF1</i>). Infection information is systemically spread over the entire seedling and propagates radially from infected to non-infected leaves, axially from leaves to roots, and <i>vice versa</i>. The local and systemic <i>NRT2.5</i> responses are reduced in the <i>jar1</i> mutant, and the <i>RRTF1</i> response in the <i>rbohD</i> mutant. Information about <i>A. brassicae</i> infection travels slowly to uninfected neighboring plants via a <i>Piriformospora Indica</i> hyphal network, where <i>NRT2.5</i> and <i>RRTF1</i> are up-regulated. The systemic <i>A. brassicae</i>-induced JA response in infected plants is converted to an abscisic acid (ABA) response in the neighboring plant where ABA and ABA-responsive genes are induced. We propose that the local threat information induced by <i>A. brassicae</i> infection is spread over the entire plant and transferred to neighboring plants via a <i>P. indica</i> hyphal network. The JA-specific response is converted to a general ABA-mediated stress response in the neighboring plant.