fpls-09-01936 January 9, 2019 Time: 15:47 # 1 ORIGINAL RESEARCH published: 11 January 2019 doi: 10.3389/fpls.2018.01936 Production and Role of Hormones During Interaction of Fusarium Species With Maize (Zea mays L.) Seedlings Josef Vrabka1, Eva-Maria Niehaus2, Martin Münsterkötter3, Robert H. Proctor4, Daren W. Brown4, Ondrejˇ Novák5,6, Aleš Penˇ cikˇ 5,6, Danuše Tarkowská5,6, Kristýna Hromadová1, Michaela Hradilová1, Jana Oklešt’ková5,6, Liat Oren-Young7, Yifat Idan7, Amir Sharon7, Marcel Maymon8, Meirav Elazar8, Stanley Freeman8, Ulrich Güldener9, Bettina Tudzynski2, Petr Galuszka1† and Veronique Bergougnoux1* Edited by: 1 Department of Molecular Biology, Centre of the Region Haná for Biotechnological and Agricultural Research, Faculty Pierre Fobert, of Science, Palacký University, Olomouc, Czechia, 2 Institut für Biologie und Biotechnologie der Pflanzen, Molecular Biology National Research and Biotechnology of Fungi, Westfälische Wilhelms-Universität Münster, Münster, Germany, 3 Functional Genomics Council Canada (NRC-CNRC), and Bioinformatics, Sopron University, Sopron, Hungary, 4 National Center for Agricultural Utilization Research, United States Canada Department of Agriculture, Peoria, IL, United States, 5 Institute of Experimental Botany, Czech Academy of Sciences, Reviewed by: Olomouc, Czechia, 6 Department of Metabolomics, Centre of the Region Haná for Biotechnological and Agricultural Nora A. Foroud, Research, Faculty of Science, Palacký University, Olomouc, Czechia, 7 Department of Molecular Biology and Ecology Agriculture and Agri-Food Canada, of Plants, Tel Aviv University, Tel Aviv, Israel, 8 Department of Plant Pathology and Weed Research, Agricultural Research Canada Organization (ARO), The Volcani Center, Rishon LeZion, Israel, 9 Department of Bioinformatics, TUM School of Life Sciences Aiping Zheng, Weihenstephan, Technical University of Munich, Munich, Germany Sichuan Agricultural University, China Rajesh N. Patkar, Maharaja Sayajirao University It has long been known that hormones affect the interaction of a phytopathogen with of Baroda, India its host plant. The pathogen can cause changes in plant hormone homeostasis directly *Correspondence: by affecting biosynthesis or metabolism in the plant or by synthesizing and secreting Veronique Bergougnoux [email protected] the hormone itself. We previously demonstrated that pathogenic fungi of the Fusarium †Deceased species complex are able to produce three major types of hormones: auxins, cytokinins, and gibberellins. In this work, we explore changes in the levels of these hormones in Specialty section: maize and mango plant tissues infected with Fusarium. The ability to produce individual This article was submitted to Plant Microbe Interactions, phytohormones varies significantly across Fusarium species and such differences likely a section of the journal impact host specificity inducing the unique responses noted in planta during infection. Frontiers in Plant Science For example, the production of gibberellins by F. fujikuroi leads to elongated rice stalks Received: 29 March 2018 Accepted: 12 December 2018 and the suppression of gibberellin biosynthesis in plant tissue. Although all Fusarium Published: 11 January 2019 species are able to synthesize auxin, sometimes by multiple pathways, the ratio of its free Citation: form and conjugates in infected tissue is affected more than the total amount produced. Vrabka J, Niehaus E-M, The recently characterized unique pathway for cytokinin de novo synthesis in Fusarium Münsterkötter M, Proctor RH, Brown DW, Novák O, Penˇ cikˇ A, appears silenced or non-functional in all studied species during plant infection. Despite Tarkowská D, Hromadová K, this, a large increase in cytokinin levels was detected in F. mangiferae infected plants, Hradilová M, Oklešt’ková J, Oren-Young L, Idan Y, Sharon A, caused likely by the up-regulation of plant genes responsible for their biosynthesis. Maymon M, Elazar M, Freeman S, Thus, the accumulation of active cytokinins may contribute to mango malformation of Güldener U, Tudzynski B, Galuszka P the reproductive organs upon infection of mango trees. Together, our findings provide and Bergougnoux V (2019) Production and Role of Hormones insight into the complex role fungal and plant derived hormones play in the fungal–plant During Interaction of Fusarium interactions. Species With Maize (Zea mays L.) Seedlings. Front. Plant Sci. 9:1936. Keywords: auxin, cytokinin, Fusarium, host–pathogen interaction, gibberellin, mango malformation disease doi: 10.3389/fpls.2018.01936 (MMD) Frontiers in Plant Science| www.frontiersin.org 1 January 2019| Volume 9| Article 1936 fpls-09-01936 January 9, 2019 Time: 15:47 # 2 Vrabka et al. Phytohormones in Fusarium–Maize Interaction INTRODUCTION (Niehaus et al., 2016). In the smut fungus Ustilago maydis, two genes encoding an indole-3-acetaldehyde dehydrogenase and a The genus Fusarium is a filamentous fungus found readily in tryptophan aminotransferase were characterized as responsible soil around the world and associated with multiple crop species. for IAA production (Reineke et al., 2008). A possible third Although it can interact with plants as an endophyte, its growth pathway for auxins could be mediated by a Fusarium gene with as a biotroph, hemibiotroph, or necrotroph cause significant homology to the plant gene YUCCA, which codes for a key agronomic losses worldwide. Currently, the genus Fusarium is enzyme in plant auxin biosynthesis (Kasahara, 2015) located divided into 20 species complexes and nine monotypic lineages between the GA and CK clusters. A contribution of the possible (O’Donnell et al., 2013). Species from the Fusarium fujikuroi YUCCA pathway to auxin production in fungi has not been yet complex (FFC) are best known for their ability to induce functionally proved. diseases such as “bakanae” in rice (Matic et al., 2017), ear and The phytohormones jasmonates, salicylic acid (SA), ethylene stalk rot in maize (Presello et al., 2008), pitch canker in pine and abscisic acid play a vital role defending plants against (Gordon, 2006) and mango malformation disease (MMD) in fungal pathogens such as Fusarium oxysporum (Dempsey mango (Freeman et al., 2014). Some disease symptoms can be and Klessig, 2012; Di et al., 2016). In contrast, the role clearly linked to hormone production by the fungi. In fact, of CKs and auxins is poorly understood. In some fungus– culture filtrate of Fusarium fujikuroi (Gibberella fujikuroi) was host interactions, CKs are essential for full virulence of the the first source from which gibberellins (GAs) were isolated and pathogen (Chanclud et al., 2016; Hinsch et al., 2016). In Ustilago identified several decades ago (Hedden and Sponsel, 2015). It was maydis, the loss of CK production leads to fewer and smaller only later discovered that GAs are ubiquitous plant hormones tumors in maize (Morrison et al., 2017). The CKs detected in that promote normal stem elongation. The contribution of Magnaporthe oryzae infected rice leaves have been proposed additional GAs to infected rice plants by F. fujikuroi leads to to serve as a signal to mobilize nutrients, to increase levels of abnormally long stems which is the typical “bakanae” symptom photosynthesis in host leaves or to activate SA-mediated defense observed. The gene cluster responsible for GA synthesis in responses (Jiang et al., 2013). In F. mangiferae infected mango F. fujikuroi has been extensively characterized (Tudzynski and trees, changes in CK and GA levels are associated with the Hölter, 1998). inflorescence and vegetative malformations and reduction in The production of other hormones such as cytokinins (CKs), fruit yield (Bist and Ram, 1986; Nicholson and van Staden, auxins and ethylene by fusaria was first suggested over 35 years 1988). ago based on their detection in culture filtrates (Manka´ , 1980; In addition to changes in GA content in rice seedlings Van Staden and Nicholson, 1989; Thakur and Vyas, 1983). infected by F. proliferatum, IAA content was twofold higher CKs can be produced by the tRNA decay pathway, which is in leaves and 1.5-fold lower in roots of a susceptible cultivar. conserved in almost all living organisms, or by de novo synthesis. In contrast, changes in a resistant cultivar of the same The tRNA pathway was shown to contribute to CK content in magnitude were reversed (Quazi et al., 2015). IAA contributes some fungi including Claviceps purpurea (Chanclud et al., 2016; to host vulnerability to a pathogen by inducing acidification Hinsch et al., 2016; Morrison et al., 2017). Recently, we found and loosening of the cell wall. Resistance to pathogens has evidence for possible de novo CK synthesis by members of been attributed to IAA-amino acid conjugating enzymes which the FFC based on whole genome sequence analysis (Niehaus lead to IAA deactivation (Fu et al., 2011). Some bacterial et al., 2016). We identified two homologous gene clusters, and fungal pathogens can “hijack” auxin metabolism in plant designated CK1 and CK2 located near the GA gene cluster. Each hosts leading to more IAA-aspartic acid (IAA-Asp) conjugate, cluster contains two genes: IPTLOG and P450. IPTLOG codes known to have a role in disease promotion (González- for an enzyme with dual activity: the isopentenyl transferase Lamothe et al., 2012). Arabidopsis roots and leaves infected domain (IPT) is responsible for the conjugation of dimethylallyl with F. oxysporum, and causing wilt disease, show alterations pyrophosphate with ATP to form a CK precursor, which is in auxin homeostasis