International Conference on Plant Peroxisome Research

SI-1 The PEX11 family: Deciphering a key player of peroxisomal proliferation Kornelija Pranjić, Johannes Koch, Anja Huber, Andreas Hartig, Cécile Brocard and Friedrich Kragler* # University of Vienna, Department of Biochemistry, Center of Molecular Biology, MFPL, Austria; * Max Planck Institute of Molecular Plant Physiology, Golm, Germany In plants, peroxisomes are involved in a variety of essential physiological and biochemical functions such as photorespiration, lipid catabolism, and hormone production. These organelles are highly versatile and quickly adjust to cellular requirements. Over 30 proteins named peroxins are suggested to be specifically involved in building and maintaining functional peroxisomes. Among these the members of the PEROXIN 11 (PEX11) protein family act as peroxisomal proliferation factors. However, the particular function(s) of PEX11 proteins and their relationship to each other are not well understood. In a collaborative effort between three laboratories, we tested all PEX11 family members from three distinct organisms yeast (ScPEX11, 25 and 27), human cells (PEX11α, β and γ), and Arabidopsis (AtPEX11A to E) for their capacity to alter peroxisomal size and shape in all three organisms. Our combined analysis of the PEX11-proteins suggests a complex interplay between PEX11 proteins and that PEX11 family members exert distinct functions. Furthermore, to identify factors controlling PEX11 expression and, consequently, peroxisomal number in A. thaliana, we studied the promoter activity of AtPEX11D. We focused on AtPEX11D as, upon transient overexpression, the protein showed the strongest effect on peroxisomal shape and size. The AtPEX11D promoter activity was evaluated under various growth conditions. In addition, we identified a putative AtPEX11D transcription factor. The gained insights advanced our understanding of the complex machinery of peroxisomal biogenesis and might allow us to find novel means to optimize lipid production in plants. Funded by a joint grant “Symbiosis and Molecular Principles of Recognition” to C.B., F.K. and A.H. from the University of Vienna. C.B. is supported by the Elise-Richter program of the Austrian