Universiteit Leiden

nl en

Paul Hooykaas

Professor emeritus of genetics

Prof.dr. P.J.J. Hooykaas
+31 71 527 4933

I am interested in the molecular mechanisms which are used by the soil bacterium Agrobacterium tumefaciens to induce crown gall tumors on plants and its applications. The bacterium accomplishes this by its exceptional ability to transfer an (oncogenic) DNA segment, the T-DNA, into host cells at the infection site. This natural ability to transfer genes into host cells can be applied for the genetic modification and genome editing of plants.

More information about Paul Hooykaas

Paul J.J. Hooykaas is Professor of Genetics, appointed as such and as  Head of both the Molecular Genetics and Yeast Genetics departments in 1993. He studied Chemistry and did his PhD research  in biochemistry and wrote a thesis entitled “ The role of plasmid determined functions in the interactions of Rhizobiaceae with plant cells”. He obtained the PhD degree in 1979  and received the C.J. Kok prize for his thesis from Leiden University.

After that he continued with his research in Leiden as a member of staff.  In 1994 he was also appointed as Professor of Molecular Genetics at Delft University of Technology and was professor in Delft for about ten years. He has acted as director of the Institute of Molecular Plant Sciences and later on of the Institute of Biology. Nowadays he is chairman of the Science Committee of the Faculty of Mathematics and Natural Sciences, chairman of the KNAW section Biology, member of the KNAW Council of Earth and Life Sciences and member of the board the Top Institute Green Genetics. 

For his scientific work he received the AKZO Prize in 1987, awarded by the Royal Holland Society of Sciences and Humanities. In 1992 he was selected as a member of the Academia Europaea and in 2003 as a member of the Royal Netherlands Academy of Arts and Sciences (KNAW). Recently, he had the honor to be  appointed as a KNAW Academy Professor.

With my close colleagues Dr. Bert van der Zaal, Dr. Paul van Heusden and Dr. Sylvia de Pater and the  help of many postdocs, PhD students, MSc and BSc students I have been studying Agrobacterium and its applications already for many years. Results have often been surprising and have taught us about the ingenious ways this bacterium manipulates host cells.  On the basis of this knowledge we have built tools that are helpful for the study and genetic modification of (cop) plants, such as the binary vector system, which was developed in our group and which is used world-wide for the construction of transgenic plants. We have more recently discovered that Agrobacterium cannot only be used for the transformation of plants, but also of yeasts and fungi. Therefore, the bacterium is now also a favorite vector for the genetic modification of many fungi and mushrooms. At the same time it allowed us to use the model yeast Saccharomyces cerevisiae in our investigations of the molecular mechanism of Agrobacterium-mediated transformation (AMT). Our discovery that besides DNA molecules also several (effector) virulence proteins are separately and independently of the T-DNA introduced into host cells during infection has led us to research aimed to develop methodology for protein therapy.

Currently the main lines of research are still related to the molecular mechanism of T-DNA transfer and tumorigenesis in plants by Agrobacterium tumefaciens :

  1. The function of translocated effector proteins, especially VirE3 and VirD5
  2. The mechanism of T-DNA integration in eukaryotic genomes
  3. The use the Agrobacterium transfer system in order to improve genome editing with CRISPR/Cas, TALENs and ZFNs and gene targeting in plants
  4. To establish protein delivery (protein therapy) as an alternative manner to change the properties of plants.

See for a more a detailed description of the projects also the personal pages from other members of Molecular and Developmental Genetics (Dr. De Pater, Dr. Van Heusden and Dr. Van der Zaal).

Professor emeritus of genetics

  • Science
  • Instituut Biologie Leiden
  • IBL Plant Sciences

Work address

Sylviusweg 72
2333 BE Leiden
Room number 5418



  • Add2X Bio Sciences Adviseur/aandeelhouder
  • KNAW Werkzaamheden in commissies/bestuur
  • NWO werkzaamheden in commissies/bestuur
This website uses cookies.  More information.