Generation of Plasmodium yoelii malaria parasite for conditional degradation of proteins.

The auxin-inducible degron (AID) system is a robust chemical-genetic method for manipulating endogenous protein level by conditional proteasomal degradation via a small molecule. So far, this system has not been adapted in the P. yoelii, an important and widely used Plasmodium rodent parasite model for malaria biology. Here, using the CRISPR/Cas9 genome editing method, we generated two marker-free transgenic P. yoelii parasite lines (eef1a-Tir1 and soap-Tir1) stably expressing the Oryza sativa gene tir1 under the promoters of eef1a and soap respectively. These two lines develop normally during the parasite life cycle. In these backgrounds, we used the CRISPR/Cas9 method to tag two genes (cdc50c and fbxo1) with the AID motif and interrogate the expression of these two proteins with auxin. The eef1a-Tir1 line allows efficient degradation of the AID-tagged endogenous protein in the asexual schizont and sexual gametocyte stages, while the soap-Tir1 line allows protein degradation in the ookinetes. These two lines will be a useful resource for studying the Plasmodium parasite biology based on the P. yoelii.