Microtubule stability affects the unique motility of F-actin in Marchantia polymorpha

Actin microfilaments play crucial roles in diverse plant functions. Some specific cellular processes require interaction between F-actin and microtubules, and it is believed that there are direct or indirect connections between F-actin and microtubules. We previously reported that actin microfilaments exhibit unique dynamic motility in cells of the liverwort, Marchantia polymorpha; the relevance of this activity to microtubules has not been explored. To examine whether the dynamics of F-actin in M. polymorpha were somehow regulated by microtubules, we investigated the effects of stabilization or destabilization of microtubules on dynamics of actin bundles, which were visualized by Lifeact-Venus. To our surprise, both stabilization and destabilization of microtubules exerted similar effects on F-actin motility; apparent sliding movement of F-actin in M. polymorpha cells was accelerated by both oryzalin and paclitaxel, with the effect of paclitaxel more evident than that of oryzalin. Immunofluorescence staining revealed that some F-actin bundles were arrayed along with microtubules in M. polymorpha thallus cells. These results suggest that microtubules play regulatory roles in the unique F-actin dynamics in M. polymorpha.