Phytocystatins are inhibitors of papain like cysteine proteases. In plants, their activity  is associated with the regulation of developmental processes, and with responses to abiotic and biotic stresses. Since many plant pests also rely on cysteine proteases for the breakdown of plant proteins, cystatins can reduce the accessibility of plant resources for the invader. Up to now research has focussed on the application of phytocystatins as pest control agents, and not very much is known about their endogenous function in planta. Our group at FABI would therefore like to find out more about the biochemistry, expression pattern and phylogenetics of phytocystatins. We also investigate their potential for the improvement of yield in plant based production of pharmaceuticals and other interesting proteins.

Together with students in the lab, I am working on the following projects:

·        LEGIM project (improvement of soybean nodule performance): The expression and activity of cysteine protease and phytocystatins during soybean nodule development will be investigated. We are particularly interested in the role of cysteine proteases during natural and drought induced senescence processes.

·        Soybean transformation: In collaboration with Dr. Rachel Chikwamba from the CSIR we establish soybean transformation at UP.

·        Studies on the reactive site of phytocystatins: Papaya and rice phytocystatins show natural variation in the amino acid sequence of the second loop motif, which is supposed to be important for binding to the protease. We will study the binding capacity of the natural occurring as well as mutated forms of phytocystatins to different proteases.

·        Yield improvement of recombinant protein production in plants: Plant based production systems suffer losses from protein degradation. We would like to explore the role of cysteine proteases in this process as well as the potential of phytocystatins for yield improvement of recombinant protein production in different cell compartments.

·        Characterisation of Amaranthus mutants:Mutant lines of Amaranthus tricolour were selected for their improved tolerance under drought stress. We characterise morphological as well as physiological features of these lines in comparison to the wild type under different environmental conditions.