Lichius, A., Lord, K. M., Jeffree, C. E., Oborny, R., Boonyarungsrit, P., & Read, N. D.
Institute of Cell Biology, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, Scotland, UK. Department of Microbiology, Centre for Scientific Research and Higher Education of Ensenada (CICESE), Carretera Ensenada-Tijuana 3918, 22860 Ensenada, Baja California, Mexico, Department of Plant Sciences, University of Oxford, South Park Road, Oxford OX1 3RB, UK, School of Engineering and Computing Sciences, Durham University, South Road, Durham.
Cell polarization and fusion are crucial developmental processes that occur in response to intracellular and extracellular signals. Asexual spores (conidia) of the mould Neurospora crassa differentiate two types of polarized cell protrusions, germ tubes and conidial anastomosis tubes (CATs), which exhibit negative and positive chemotropism, respectively. We provide the first evidence that shared and separate functions of the Rho-type GTPases CDC-42 and RAC-1 regulate these opposite chemotropisms. We demonstrate that RAC-1 is essential for CAT formation and cell fusion, whereas CDC-42 is necessary and sufficient for normal germ tube development. Cdc42-Rac-interactive-binding (CRIB) reporters were constructed to exclusively label locally activated GTP-bound GTPases. Time course analyses showed that repositioning of these activated GTPase clusters within germ tube and CAT tip apices controls directional growth in the absence of a tip-localized vesicle supply centre (Spitzenkorper). We propose a model in which the local assembly of a plasma-membrane-associated GTPase-PAK-MAPK signalling platform regulates chemoattractant perception and secretion in order to synchronize oscillatory cell-cell communication and directional CAT tip growth.
… “For widefield epifluorescence microscopy, the same microscope and objectives were used with: a CoolLED pE-2 excitation system; a 550 nm LED array”…
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pE-2: A repeatable, controllable modular system with 20 different LED peaks. Instant on/off and intensity (0-100%) control.
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