In vivo assessment by Mach-Zehnder double-beam interferometry of the invasive force exerted by the Asian soybean rust fungus (Phakopsora pachyrhizi).
Asian soybean rust (Phakopsora pachyrhizi) causes a devastating disease in soybean (Glycine max). We tested the hypothesis that the fungus generates high turgor pressure in its hyaline appressoria to mechanically pierce epidermal cells. Turgor pressure was determined by a microscopic technique, called transmitted light double-beam interference Mach-Zehnder microscopy (MZM), which was developed in the 1960s as a forefront of live cell imaging. We revitalized some original microscopes and equipped them for modern image capturing. MZM data were corroborated by cytorrhysis experiments. Incipient cytorrhysis determined the turgor pressure in appressoria of P. pachyrhizi to be equivalent to 5.13 MPa. MZM data revealed that osmotically active sugar alcohols only accounted for 75% of this value. Despite having a lower turgor pressure, hyaline rust appressoria were able to penetrate non-biodegradable polytetrafluoroethylene (PTFE) membranes more efficiently than do melanized appressoria of the anthracnose fungus Colletotrichum graminicola or the rice blast fungus Magnaporthe oryzae. Our findings challenge the hypotheses that force-based penetration is a specific hallmark of fungi differentiating melanized appressoria and that this turgor-driven process is solely caused by metabolic degradation products. The appressorial turgor pressure may explain the capability of P. pachyrhizi to forcefully invade a wide range of different plants and may pave the way to novel plant protection approaches.
Department of Plant Physiology, RWTH Aachen University, D-52056, Aachen, Germany.
Marco
M
Loehrer
Department of Plant Physiology, RWTH Aachen University, D-52056, Aachen, Germany.
Jens
J
Botterweck
Department of Soil Ecology, RWTH Aachen University, D-52056, Aachen, Germany.
Joachim
J
Jahnke
Technology of Optical Systems (TOC), RWTH Aachen University, D-52056, Aachen, Germany.
Daniel M
DM
Mahlmann
Institute of Bio- and Geosciences: IBG-1 Biotechnology, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
Jochem
J
Gaetgens
Institute of Bio- and Geosciences: IBG-1 Biotechnology, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
Marco
M
Oldiges
Interdisciplinary Centre for Crop Plant Research (IZN), Martin-Luther-University Halle-Wittenberg, D-06120, Halle (Saale), Germany.
Ralf
R
Horbach
Interdisciplinary Centre for Crop Plant Research (IZN), Martin-Luther-University Halle-Wittenberg, D-06120, Halle (Saale), Germany.|Institute of Agricultural and Nutritional Sciences, Phytopathology and Plant Protection, Martin-Luther-University Halle-Wittenberg, D-06120, Halle (Saale), Germany.
Holger
H
Deising
Department of Plant Physiology, RWTH Aachen University, D-52056, Aachen, Germany.
Ulrich
U
Schaffrath
D001487:Basidiomycota / Q000737:chemistry / Q000472:pathogenicity*; D008401:Gas Chromatography-Mass Spectrometry; D018525:Germination; D006003:Glycogen / Q000378:metabolism; D054884:Host-Pathogen Interactions; D007091:Image Processing, Computer-Assisted; D007368:Interferometry / Q000295:instrumentation / Q000379:methods*; D020082:Magnaporthe / Q000472:pathogenicity; D008567:Membranes, Artificial; D009995:Osmosis; D010935:Plant Diseases / Q000382:microbiology*; D011138:Polytetrafluoroethylene; D013025:Glycine max / Q000382:microbiology*; D013402:Sugar Alcohols / Q000032:analysis / Q000378:metabolism
D008567:Membranes, Artificial; D013402:Sugar Alcohols; D011138:Polytetrafluoroethylene; D006003:Glycogen
Asian soybean rust (Phakopsora pachyrhizi); appressorial turgor pressure; cytorrhysis; interferometry; melanin; penetration by force; sugar alcohols