I. Understanding Cell Shape: Big Insights From Little Plants
II. Using Reverse Genetics to Dissect the Formin Gene Family
III. Myosin and Actin Steer Plant Cell Division
Part II: Using Reverse Genetics to Dissect the Formin Gene Family
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Magdalena Bezanilla’s lab is interested in understanding what determines cell shape at the molecular level. In Part 1 of her talk, Bezanilla explains why the moss, Physcomitrella patens, is an excellent model system to address this question. P. patens grows quickly and entire plants can be vegetatively regenerated from single cells. The genome is sequenced and its cells undergo efficient homologous recombination- the only plant known to do this! In the filamentous tissue that establishes the plant, cells at the tips grow in a polarized manner as flexible cell wall material is incorporated and then pushed out by turgor pressure. To study the role of actin in determining cell shape, Bezanilla’s lab used a live-cell actin binding probe to label actin and imaged cell growth with fluorescence microscopy. They showed that polarized growth depended on the rapid disassembly and assembly of actin filaments; processes regulated by actin binding proteins.
Formins are a family of actin binding proteins that help to nucleate and elongate actin filaments. In Part 2 of her talk, Bezanilla describes experiments in which her lab used RNA interference to examine the role of the formin gene family in Physcomitrella. They showed that class II formins specifically are required for polarized growth and that they actively generate new actin filaments at the cell cortex and the cell tip.
In Part 3, Bezanilla examines the role of myosins in plant cell division. Thirty-five classes of myosins are known, yet, only two classes, myosins VIII and XI are found in plants. While Myosin XI is required for cell viability, myosin VIII is not. However, myosin VIII mutants have improperly positioned cell plates or cell division defects. Results from Bezanilla’s lab detail the molecular role of myosin VIII in plant cell division.
Magdalena Bezanilla’s lab investigates the role of the actin cytoskeleton in regulating cell growth and cell shape in plants. She has promoted the use of the moss Physcomitrella patens because of its ability to undergo homologous recombination, a trait that, among land plants, is unique to Physcomitrella. Her lab has developed numerous other tools that have allowed them to understand the molecular basis of cell growth in plants.
Bezanilla began her university studies at the University of California, Santa Barbara as a physics undergraduate. She changed her focus as a graduate student and received her PhD in biochemistry, cellular and molecular biology from Johns Hopkins University School of Medicine. She was introduced to the study of moss as a post-doctoral fellow with Ralph Quatrano at Washington University in St. Louis. In 2005, Bezanilla joined the faculty at the University of Massachusetts in Amherst where she was Professor of Biology until 2017. She recently moved to Dartmouth College where she is E.E. Just Chair in the Department of Biological Sciences.
Bezanilla had received numerous awards for her contributions to cell biology including the Faculty Early Career Development Award from the National Science Foundation, the American Society for Cell Biology Women in Cell Biology Junior Career Recognition Award and the 2010 Presidential Early Career Award for Scientists and Engineers.
Learn more about Bezanilla’s research here.
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Vidali L, Bezanilla M. Physcomitrella patens: a model for tip cell growth and differentiation. Curr Opin Plant Biol. 2012 Dec;15(6):625–31.
Augustine RC, Pattavina KA, Tüzel E, Vidali L, Bezanilla M. Actin interacting protein1 and actin depolymerizing factor drive rapid actin dynamics in Physcomitrella patens. Plant Cell. 2011 Oct;23(10):3696–710.
Vidali L, van Gisbergen PAC, Guérin C, Franco P, Li M, Burkart GM, et al. Rapid formin-mediated actin-filament elongation is essential for polarized plant cell growth. Proc Natl Acad Sci USA. 2009 Aug 11;106(32):13341–6.
van Gisbergen PAC, Li M, Wu S-Z, Bezanilla M. Class II formin targeting to the cell cortex by binding PI(3,5)P(2) is essential for polarized growth. J Cell Biol. 2012 Jul 23;198(2):235–50.
Wu S-Z, Ritchie JA, Pan A-H, Quatrano RS, Bezanilla M. Myosin VIII regulates protonemal patterning and developmental timing in the moss Physcomitrella patens. Mol Plant. 2011 Sep;4(5):909–21.
Wu S-Z, Bezanilla M. Myosin VIII associates with microtubule ends and together with actin plays a role in guiding plant cell division. eLife 2014 Sep 23;3:e03498.