My main aim is to understand, in molecular detail, how plants recognise pathogens and mount an effective defence response. Thereto, three research lines are pursued in my group. The eldest line focuses on function of NLR immune receptors in disease resistance. Earlier, we found that these proteins act as nucleotide-operated molecular switches, whose conformation changes upon pathogen perception (Fig 1 and i.e. Takken and Tameling, Science 2009, Takken and Goverse, COPB 2012). Recently we reported, in collaboration with the Cann laboratory (Durham UK), that the NB-ARC domain (Fig 2) NLR proteins can bind and bend DNA in vivo, and that DNA binding in planta requires proper activation by the genuine pathogen (Fenyk et al, JBC 2015). This exciting finding defines DNA as the first conserved molecular target of an NLR protein and in a recently funded VICI project the role of DNA binding by NLR proteins for plant immunity is chased.
Disease resistance can also be conferred by a lack of compatibility with a given pathogen (van Schie and Takken, Ann. Rev. Phytopathol 2015). In the second research line we focus on the identification of compatibility/susceptibility genes by screening for host protein targets that are manipulated by a pathogen. Our main model is the interaction between tomato and the soil-borne fungal pathogen Fusarium oxysporum fsp. lycopersici. Fusarium colonizes the xylem vessels of a plant causing wilt disease. During infection the fungus secretes many small proteins in the xylem sap that are referred to as Six (Secreted In Xylem) proteins. Many Six proteins promote disease development, like Six6 (Gawehns et al MPMI 2014) or Six3 (Avr2) (Houterman et al 2009 Plant J) that acts in the nucleus (Ma et al Front Plant Sci 2013) in conjunction with Six5 (Ma et al New Phytol 2015). Besides enhancing virulence Avr2 is also triggering an I-2 specific immune response (Fig 3). Using Six proteins as probes we have successfully identified specific plant proteins whose knockout result in increased disease resistance. Identification of these susceptibility genes increases our understanding on how a pathogen manipulates its host providing new leads to combat diseases (Gawehns et al, Micr. Biotech 2013).
In my 3 rd and newest research line we focus on the intriguing observation that colonisation by endophytic fungi can enhance disease resistance to biotic and abiotic stresses. In this project we study a) how endophytes evade host resistance while at the same time enhance immunity and b) how endophytes differ from pathogens, being both able to overcome defences and colonise the host, yet with a different outcome for the latter.
The Plant Pathology group is headed by Prof.dr. Ben Cornelissen. The group is divided into three subgroups: my "plant" group, the "fungus" group and the "Sumo" group, the latter groups are headed by respectively dr. Martijn Rep and Dr. Harrold van den Burg.
Prof Marcel Prins is appointed a special chair Virology in the Plant Pathology group and in close collaboration these groups study the molecular interaction between plants and their (fungal) pathogens.
Dr Marijn Knip
Postdoc - VICI project: Linking plant immunity and DNA damage.
Dr Manon Richard
Postdoc - VICI project: Linking DNA binding of plant NLR proteins to plant immunity.
Dr Nico Tintor
Postdoc - Collaboration ENZA/MPP: The role of effector uptake in plant immunity.
PhD student - VICI project: Elucidating the molecular mechanism underlying the virulence and avirulence functions of the Fusarium Avr2/Six5 effector pair.
Technician - VICI project: supporting the VICI project in various ways.
Francisco de Lamo Ruiz (shared supervision with Dr M Rep)
PhD student - ETN Horizon2020 : How do endophytes evade host resistance while enhancing immunity?
Maria Constantin (shared supervision with Dr M Rep)
PhD student - ETN Horizon202: “How do endophytes differ from pathogens?”
Former lab members
PhD student: Elucidating the molecular mechanism underlying the virulence and avirulence functions of the Fusarium Avr2/Six5 effector pair
PhD student: The Avr2 effector protein from Fusarium as a guide to unravel plant innate immunity.
Technician: involved in all ongoing projects in the group.
Dr Hanna Richter
Technician: involved in all ongoing projects in the group.
ir. Lisong Ma
PhD student: Analysing the intrinsic functions of Avr2 and its perceival by the resistance protein I-2.
PhD student: Functional characterisation of Fusarium secreted effector proteins in disease and resistance
ir. Ewa Lukasik
PhD student: focussing on the ATPase activity of the NBS domain of R proteins and the identification of interacting protein
drs Vladimir Krasikov
Postdoc analyzing the role of the Xsp10 protein for resistance anddisease to Fusarium oxysporum
dr. ir. Harrold van den Burg
Veni Postdoc studying the role of SUMO modification in plant defence signalling
ing Marianne de Vroomen
Technician, involved in most ongoing projects.
Drs Mobien Kasiem
PhD student: PhD student: Structure and function of tomato disease resistance proteins
Dr Gerben van Ooijen
PhD student: Structure and function of tomato disease resistance proteins
Dr Klaas Jan de Vries
Postdoc: Targeted proteomics of signalosomes mediating pathogen resistance
Dr Wladimir Tameling
PhD student: Disease resistance proteins of the NBS-LRR class, molecular switches of plant defence
Dr Sergio de la Fuente van Bentem
PhD student: Unfolding plant disease resistance, the involvement of HSP90 and its co-chaperone PP5 in I-2 mediated signalling
Dr Jack Vossen
Postdoc: Characterisation of the I-2 signalosome
Dr Sandra Elzinga
Postdoc: Characterisation of the Mi-1 signalosome
Selection from the last ten years
Frank Takken (1969) is interested in how plants defend themselves against pathogens. Plants are able to sense the presence of invading microbes. Recognition subsequently results in activation of the plant innate immune system. In this process, resistance proteins play a key role as they mediate pathogen recognition and trigger the activation of downstream signaling cascades that halt the pathogen and thereby prevent disease. An example of a succesfull immune response is shown in the figure below where the tomato Immunity-2 ( I-2) gene halts ingress of the pathogenic fungus Fusarium oxysporum.
Resistance genes come in different flavors, but the majority encodes intracellular tri-partite proteins that contain a central nucleotide-binding domain. One of Frank's major research interests is the role the distinct domains in these proteins have for their function. Structure-function analysis in combination with 3D modeling of the different subdomain is used to predict mutations that will have specific effects on the activity of these proteins. These mutants are subsequently analyzed for altered biochemical properties, differences in inter- and intramolecular interactions as well as for their effect on disease resistance.
To examine how resistance proteins activate downstream signaling it is essential to know their interacting partners. Using various screens, candidate interacting proteins, and recently also DNA, have been identified and these interactors are analyzed for their involvement in plant defense.
Frank is appointed as Associate professor in the Molecular Plant Pathology group at the Swammerdam Institute for Life Sciences and is since 2012 Scientific Advisor for Scienza Biotechnology. Earlier he
worked as postdoc at the Phytopathology group at Wageningen University. During this time he worked on a self-written project at the biotech company Keygene NV in Wageningen. In that project he focused on the identification of genes that are transcriptionally regulated during the onset of plant defense signaling. He received his PhD in 1999 from the Free University of Amsterdam for his pioneering work on the isolation of resistance genes from tomato.
A resistant tomato plant carrying I-2 (left) and susceptible one (right side) infected with Fusarium oxysporum f.sp. lycopersici.