Contents lists available at ScienceDirect Plant Physiology and Biochemistry journal homepage: www.elsevier.com/locate/plaphy Research article Grape phylloxera (D. vitifoliae) manipulates SA/JA concentrations and signalling pathways in root galls of Vitis spp. Markus W. Eitle a,∗ , Michaela Griesser a , Radomira Vankova b , Petre Dobrev b , Simone Aberer a , Astrid Forneck a a Institute of Viticulture and Pomology, Department of Crop Sciences, University of Natural Resources and Life Sciences (BOKU), Vienna, Konrad Lorenz Strasse 24, 3430, Tulln an der Donau, Austria b Institute of Experimental Botany, Institute of Experimental Botany, Czech Academy of Sciences, Rozvojová 263, 16502, Praha 6, Prague, Czech Republic ARTICLE INFO Keywords: Grape phylloxera Insect probing Plant defence Root gall formation SA/JA signalling Vitis spp ABSTRACT Overcoming host defensive traits is a prerequisite to establish compatible plant-parasite interactions. Following parasite perception, jasmonic (JA) and salicylic acid (SA) signalling pathways mediate biotic stress signals re- sulting in the activation of host defence responses. Piercing-sucking grape phylloxera (Daktulosphaira vitifoliae) infests Vitis spp. by the formation of organoid root galls. This study aims to investigate whether host defensive SA/JA signalling pathways are affected during D. vitifoliae infestation. We hypothesize that the JA signalling pathway is induced during larval probing (14 hai). Compatible root gall formation (24 hai − 14 dai) involves the reduction of the JA, but the induction of the SA signaling pathway. T5C (V. berlandieri x V. riparia) cuttings are infested with a D. vitifoliae single founder lineage (biotype C). Phytohormone quantification (HPLC-MS) and transcriptional alterations of JA/SA marker genes (qRT-PCR) are determined in root tissues from larval probing (14 hai) until gall formation (> 14 dai). Non-infested root tips are considered controls. Our results show a significant induction of all analysed JA marker genes during insect probing (14 hai), but their significant re- duction during early gall formation (24 hai). Following gall formation (5–14 dai) SA and JA-Ile increase. However, only the analysed SA marker genes are induced, whereas JA marker gene expression levels are sig- nificantly reduced. Based on this data we conclude that the observed suppression of the JA signalling pathway might represent an important step for the compatible D. vitifoliae – Vitis spp. root interaction. We discuss whether the induced SA defences protect nutritive root galls against soil microbes. 1. Introduction Plants possess a large number of genetically conserved and complex defence mechanisms. Among them the two phytohormones jasmonic acid (JA) and salicylic acid (SA) mediate biotic stress signals and acti- vate downstream host defence responses in plant tissues under attack (Erb et al., 2012). Phytophagous insects, with different feeding beha- viours, were shown to interfere with plant host defences mediated by JA and SA signalling pathways in order to establish compatible host- parasite interactions efficiently (De Vos et al., 2005). The introduction of grape phylloxera (Daktulosphaira vitifoliae Fitch) in Europe is one of the most famous examples for an introduced insect pest species causing severe economic damages to the viticulture in the 19th century. Today, reports of D. vitifoliae root infestation increase worldwide due to the evolution of aggressive D. vitifoliae biotypes (Forneck et al., 2016) and in dependance of environmental factors (Powell et al., 2013). Root-galling D. vitifoliae feed on the parenchymal cellular content of previously formed organoid root galls on susceptible and tolerant Vitis spp. hosts (Forneck et al., 2002). Similar to other piercing-sucking insects, mobile D. vitifoliae L1 larvae are observed to probe Vitis spp. by puncturing the root tissue with their stylets; thereby selecting a suitable location for feeding site induction (Kingston, 2011). Sedentary L2-L4 larvae establish the root tip feeding site and form hook-shaped, yellowish root galls. Adult insect stages (A) feed on the https://doi.org/10.1016/j.plaphy.2019.09.024 Received 20 August 2019; Received in revised form 15 September 2019; Accepted 17 September 2019 Abbreviations: (cisOPDA), cis-12-oxophytodienoic acid; D. vitifoliae,(Daktulosphaira vitifoliae, grape phylloxera); (dai), days after inoculation; (hai), hours after inoculation; (JA), jasmonic acid; (JA-Ile), jasmonic acid isoleucine; L2/3/4-A, (grape phylloxera life stages); (MeJA), methyl jasmonate; (MeSA), methyl salicylate; (SA), salicylic acid; (T5C), Teleki 5C; Vitis spp, (Vitis species, referring to V. vinifera L. and rootstock hybrids) ∗ Corresponding author. Institute of Viticulture and Pomology BOKU, Vienna, Konrad Lorenz Straße 24, 3430, Tulln an der Donau, Austria. E-mail addresses: markus.eitle@boku.ac.at (M.W. Eitle), michaela.griesser@boku.ac.at (M. Griesser), vankova@ueb.cas.cz (R. Vankova), dobrev@ueb.cas.cz (P. Dobrev), Simone_aberer@hotmail.com (S. Aberer), astrid.forneck@boku.ac.at (A. Forneck). Plant Physiology and Biochemistry 144 (2019) 85–91 Available online 18 September 2019 0981-9428/ © 2019 Elsevier Masson SAS. All rights reserved. T