Myosin XI drives polarized growth by vesicle focusing and local enrichment of F-actin in Physcomitrium patens |
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Authors: | Giulia Galotto Pattipong Wisanpitayakorn Jeffrey P Bibeau Yen-Chun Liu Fabienne Furt Ellen C Pierce Parker J Simpson Erkan Tüzel Luis Vidali |
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Institution: | 1. Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA;2. Bioengineering Department, Temple University, Philadelphia, Pennsylvania 19122, USA;3. Bioinformatics and Computational Biology Program, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA |
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Abstract: | In tip-growing plant cells, growth results from myosin XI and F-actin-mediated deposition of cell wall polysaccharides contained in secretory vesicles. Previous evidence showed that myosin XI anticipates F-actin accumulation at the cell’s tip, suggesting a mechanism where vesicle clustering via myosin XI increases F-actin polymerization. To evaluate this model, we used a conditional loss-of-function strategy by generating moss (Physcomitrium patens) plants harboring a myosin XI temperature-sensitive allele. We found that loss of myosin XI function alters tip cell morphology, vacuolar homeostasis, and cell viability but not following F-actin depolymerization. Importantly, our conditional loss-of-function analysis shows that myosin XI focuses and directs vesicles at the tip of the cell, which induces formin-dependent F-actin polymerization, increasing F-actin’s local concentration. Our findings support the role of myosin XI in vesicle focusing, possibly via clustering and F-actin organization, necessary for tip growth, and deepen our understanding of additional myosin XI functions.Vesicle clustering by the molecular motor myosin XI enhances actin polymerization-dependent motility and polarized vesicle accumulation in tip-growing cells. |
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