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Jasmonic acid has a dominant role in Cucumber mosaic virus induced aphid resistance in Arabidopsis thaliana

Trisna Tungadi: University of Cambridge

<div>The Cucumovirus <em>Cucumber mosaic virus</em> (CMV) has a very broad host range which includes important crop plants and is non-persistently transmitted by the generalist aphid, <em>Myzus persicae</em>. CMV infection of <em>Arabidopsis thaliana</em> reduces <em>M. persicae</em> growth rate and reproduction, and inhibits prolonged aphid feeding. This might promote virus transmission rates. CMV manipulation of host plant innate immunity may determine whether CMV induces susceptibility or resistance to aphids. The exact mechanisms underlying these phenomena are not known. We used Arabidopsis single and combinatorial mutants in salicylic acid (SA), jasmonic acid (JA), ethylene and PAD4-mediated signalling pathways. We explored whether one or more of these immune signalling pathways contribute to CMV-induced resistance to <em>M. persicae</em>. Because the CMV 2b protein enhanced SA-dependent signalling but blocked JA-dependent signalling in Arabidopsis, we investigated whether JA signalling is required for CMV-induced aphid resistance. CMV-induced aphid resistance is decreased in the <em>coi1-16</em> Arabidopsis mutant that is unable to perceive JA and the resistance is completely abolished in the <em>dde2-2</em> mutant which is deficient in JA signalling. CMV-induced aphid resistance still occurred in SA-deficient <em>sid2</em> mutant and <em>NahG</em> transgenic plants. This indicates that SA is dispensable. CMV-induced aphid resistance occurs in PAD4 single mutant but was neutralised in <em>dde2-2/pad4-1</em> double mutant plants. Aphid resistance is also neutralised on CMV-infected <em>dde2-2/sid2-2</em>, <em>dde2-2/ein2-1/pad4-1</em> and in <em>dde2-2/pad4-1/sid2-2</em> mutant plants. These results show that JA-signalling is needed for CMV-induced aphid resistance in Arabidopsis.</div>