Myosin XI Interacting with a RabE GTPase Is Required for Polarized Growth

Abstract

The fundamental eukaryotic process of intracellular trafficking requires the interconnected activity of molecular motors trafficking vesicular cargo within a dynamic cytoskeletal network. However, in plants, few mechanistic details are known about how molecular motors associate with their secretory cargo to support the ubiquitous processes of polarized growth and cell division. A yeast two-hybrid screen of a Physcomitrella patens library identified a RabE GTPase as an interactor of myosin XI and subsequently demonstrated all five RabE members interact with myosin XI. Consistent with a role in polarized transport, we observed RabE at the growing cell apex and at the expanding cell plate during cell division. An in vivo cross-correlation analysis of fluorescently tagged RabE and myosin XI revealed that both species are spatiotemporally coupled, demonstrating their simultaneous involvement in polarized growth. To determine if myosin XI and RabE are directly coupled, we first computationally predicted myosin XI:RabE interface through a homology modeling-directed approach. We identified a structurally conserved residue on myosin XI, V1422, that when mutated abolished RabE binding in the yeast two-hybrid system and resulted in unpolarized plants instead of the characteristic network of filamentous cells when regenerated from single cells. Together, this work demonstrates the requirement of a direct myosin XI:RabE interaction for polarized growth in plants. Fendrych, M., Synek, L., Pečenková, T., Toupalová, H., Cole, R., Drdová, E., Nebesářová, J., Šedinová, M., Hála, M., and Fowler, J.E. (2010). The Arabidopsis exocyst complex is involved in cytokinesis and cell plate maturation. Plant Cell 22, 3053-3065. Furt, F., Lemoi, K., Tuzel, E., and Vidali, L. (2012). Quantitative analysis of organelle distribution and dynamics in Physcomitrella patens protonemal cells. . PHYML Online--a web server for fast maximum likelihood-based phylogenetic inference. Nucleic Acids Res. 33, W557-559. Guindon, S., Dufayard, J.F., Lefort, V., Anisimova, M., Hordijk, W., and Gascuel, O. (2010). New algorithms and methods to estimate maximum-likelihood phylogenies: assessing the performance of PhyML 3.0. Syst. Biol. 59, 307-321. Hammer, J.A., and Sellers, J.R. (2012). Walking to work: roles for class V myosins as cargo transporters. Nat Rev Mol Cell Bio 13, 13-26. Hashimoto, K., Igarashi, H., Mano, S., Takenaka, C., Shiina, T., Yamaguchi, M., Demura, T., Nishimura, M., Shimmen, T., and Yokota, E. (2008). An isoform of Arabidopsis myosin XI interacts with small GTPases in its C-terminal tail region. J. Exp. Bot. 59, 3523-3531. Heider, M.R., and Munson, M. (2012). Exorcising the exocyst complex. Traffic 13, 898-907. Hepler, P.K., and Winship, L.J. (2015). The pollen tube clear zone: Clues to the mechanism of polarized growth. . (2018). The Physcomitrella patens chromosome-scale assembly reveals moss genome structure and evolution. Plant J 93, 515-533. Lepore, D., Spassibojko, O., Pinto, G., and Collins, R.N. (2016). Cell cycle-dependent phosphory...

Arabidopsis Myosin XIK Interacts with the Exocyst Complex to Facilitate Vesicle Tethering during Exocytosis

“…One study in Arabidopsis identified two Rab GTPases, RabD1 and RabC2a, through a yeast two-hybrid screen using the myosin XI2 tail; however, RabC2a was shown to localize to peroxisomes and RabD mainly mediates ER to Golgi trafficking (Zheng et al, 2005;Hashimoto et al, 2008). A recent study identified RabE as a myosin XI partner in the moss Physcomitrella patens and this interaction is important for polarized growth (Orr et al, 2019). Further investigations are required to determine whether this interaction is conserved across different plant species and also functions in diffusely-growing cells.…”

“…In the moss Physcomitrella patens, myosin XI interacts with a RabE GTPase that is homologous to yeast Sec4; disruption of this binding results in unpolarized growth (Orr et al, 2019). Another study in tobacco pollen tubes showed that the MyoB family protein RISAP interacts with the RAC/ROP GTPase RAC5 and is proposed to mediate secretory trafficking during pollen tube tip growth (Stephan et al, 2014).…”