Novel functions for Arabidopsis thaliana plant defensins

Plant defensins (PDFs) are small, cysteine-rich peptides that are structurally related to insect and mammalian defensins. They were originally isolated based on their antifungal activity and consequently believed to play a crucial role in the innate immune system of plants. However,accumulating evidence suggests additional in vivo functions for those peptides in general plant development. Surprisingly, however, no clear evidence for any of these biological functions has been provided yet for PDFs of the model plant Arabidopsis thaliana (AtPDFs). While originally 15 AtPDFs were identified, more recent studies indicate 317 defensin-like genes (AtPDFLs) in this plant. In this project we aim at providing alternative modes of action and functions for two A. thaliana plant defensins relevant for defense and/or root development, and for which preliminary results are available. The proposed in-depth approach, consisting of 5 well-defined work packages, will focus on (i) root and disease phenotyping of transgenic plants with modulated expression of the two AtPDFLs as well as of plants treated with recombinant AtPDFLs, (ii) transcriptomic profiling and (iii)identifying plant protein interactors as well as lipid interactors of AtPDFLs. With this unique and challenging methodology we are convinced that we will be able to confirm the hypothesis that these antimicrobial peptides evolved towards additional functions in plants.