Myosin-5, kinesin-1 and myosin-17 cooperate in secretion of fungal chitin synthase.
Plant infection by pathogenic fungi requires polarized secretion of enzymes, but little is known about the delivery pathways. Here, we investigate the secretion of cell wall-forming chitin synthases (CHSs) in the corn pathogen Ustilago maydis. We show that peripheral filamentous actin (F-actin) and central microtubules (MTs) form independent tracks for CHSs delivery and both cooperate in cell morphogenesis. The enzyme Mcs1, a CHS that contains a myosin-17 motor domain, is travelling along both MTs and F-actin. This transport is independent of kinesin-3, but mediated by kinesin-1 and myosin-5. Arriving vesicles pause beneath the plasma membrane, but only ~15% of them get exocytosed and the majority is returned to the cell centre by the motor dynein. Successful exocytosis at the cell tip and, to a lesser extent at the lateral parts of the cell requires the motor domain of Mcs1, which captures and tethers the vesicles prior to secretion. Consistently, Mcs1-bound vesicles transiently bind F-actin but show no motility in vitro. Thus, kinesin-1, myosin-5 and dynein mediate bi-directional motility, whereas myosin-17 introduces a symmetry break that allows polarized secretion.
Department of Biosciences, University of Exeter, Exeter, UK.
Martin
M
Schuster
Steffi
S
Treitschke
Sreedhar
S
Kilaru
Justin
J
Molloy
Nicholas J
NJ
Harmer
Gero
G
Steinberg
D002687:Chitin Synthase / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D016547:Kinesins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D014588:Ustilago / Q000201:enzymology* / Q000378:metabolism
D005656:Fungal Proteins; D002687:Chitin Synthase; D009218:Myosins; D016547:Kinesins