EB1 decoration of microtubule lattice facilitates spindle-kinetochore lateral attachment in Plasmodium male gametogenesis

Abstract

Faithful chromosome segregation of 8 duplicated haploid genomes into 8 daughter male gametes is essential for male gametogenesis and mosquito transmission of Plasmodium. Plasmodium evolves the endomitosis for this multinucleated cell division. However, the mechanism underlying the spindle-kinetochore attachment remains elusive. End-binding proteins (EBs) are the conserved microtubule (MT) plus-end binding proteins and play an important role in regulating MT plus-end dynamics. Here we report that Plasmodium EB1 is a unique orthologue distinct from the canonical eukaryotic EB1. Both in vitro and in vivo assays revealed that Plasmodium EB1 lost MT plus-end tracking but gained MT-lattice affinity. This MT-binding feature of EB1 is contributed by both the CH domain and the linker region. EB1-deficient parasites produce male gametocytes that develop to the anucleated male gametes, leading to defective mosquito transmission of parasite. EB1 is localized at the nucleoplasm of male gametocytes. Upon gametogenesis, EB1 decorates the full-length of spindle MTs and regulates spindle structure. The kinetochores attach to spindle MTs laterally throughout three rounds of endomitosis and this attachment is EB1-dependent. Consequently, impaired spindle-kinetochore attachment was observed in EB1-deficient parasites. These results indicate that a parasite-specific EB1 with MT-lattice affinity has evolved to fulfill the spindle-kinetochore lateral attachment in male gametogenesis.