Processing in transgenic Arabidopsis thaliana plants of polyproteins with linker peptide variants derived from the Impatiens balsamina antimicrobial polyprotein precursor

We have previously developed a method for expression in Arabidopsis thaliana L. of transgenes encoding cleavable chimaeric polyprotein precursors. The polyprotein precursors consisted of a leader peptide and two different antimicrobial proteins (AMPs), DmAMP1 originating from Dahlia merckii seeds and a variant form of RsAFP2 originating from Raphanus sativus seeds, which were linked by an intervening linker peptide sequence originating from a natural polyprotein occurring in seeds of Impatiens balsamina. By altering the amino acid sequence of the linker peptide separating the two AMPs, we now show that it is possible to improve the accuracy of polyprotein precursor cleavage, leading to the release of both the AMPs with either no or a few additional amino acids derived from the linker peptide. Furthermore, subcellular localization indicated that both the AMPs are predominantly present in the extracellular fluid of the transgenic plants.