Fig 8.

MAG analyses lend insight on Rickettsia interactions with host actin cytoskeleton and rvh T4SS function. Black boxes provide short names for 29 MAGs from Davison et al. (73). (A) MAGs shed light on the evolution of Rickettsia factors behind host actin polymerization and invasion. Tisiphia and BG rickettsiae taxa, as well as SWAMP, SWA-VBD, RickA, and RalF info, are from Fig. 2. The passenger domains of Rickettsia conorii Sca2 (AAL02648), R. typhi dSca2 (AAU03539), R. bellii Sca2-6 (ABE05361), R. conorii Sca0 (AAL03811), R. typhi Sca3 (AAU03915), R. typhi Sca1 (AAU03504), and R. typhi Sca5 (AAU04158) were used in BlastP searches directly against Tisiphia and BG rickettsiae genomes. Passenger domains and linker sequences were delineated as previously shown (91). ReBt, Rickettsia spp. MEAM1, wb, and wq (endosymbionts of Bemisia tabaci). (B) Some Rickettsia genomes encode one or more host actin nucleation proteins. Top: Tisiphia and Rickettsia RickA proteins share a large N-terminal repeat domain but diverge at their C-termini.. Further details on RickA architecture are provided in Fig. S8. Bottom: Sca2, d-Sca2, and Sca2-6 proteins have a common autotransporter domain (β) but divergent passenger domains. FH2, formin homology 2. Sca2 mimics host formin actin nucleators (149) to recruit and polymerize actin for intracellular motility and intercellular spread (150, 151). The functions of dSca2 and Sca2/6 are unknown. (C) The mobile nature of CDI-like/Rhs-like C-terminal toxin/antidote (CRCT/CRCA) modules across diverse rickettsial genomes. Schema shows the integration of CRCT/CRCA modules into larger polymorphic toxins (hemagglutinin-like toxins, LysM-like peptidoglycan/chitin-targeting toxins, etc.), as well as CRCT/CRCA modules independent of larger toxins. The toxin warhead for RZI45292 is unknown. Further details are provided in Fig. S9.