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Differences between appressoria formed by germ tubes and appressorium-like structures developed by hyphal tips in

Ling-An Kong1, Guo-Tian Li, Yun Liu

  • 1NWAFU-Purdue Joint Research Center, College of Plant Protection, Northwest A&F University, Yangling, Shaanxi 712100, China.

Fungal Genetics and Biology : FG & B
|April 18, 2013
PubMed

Insights

The rice blast fungus Magnaporthe oryzae forms two types of infection structures: appressoria from germ tubes and appressorium-like structures from hyphal tips. These processes involve distinct molecular mechanisms, despite sharing some structural similarities.

Area of Science:

  • * Plant Pathology
  • * Mycology
  • * Molecular Biology

Background:

  • * Melanized appressoria are critical infection structures for the rice blast fungus, Magnaporthe oryzae.
  • * Appressoria are formed by germ tubes, while appressorium-like structures form on hyphal tips, with the latter being less understood.
  • * Previous work showed CHS7 mutants form appressorium-like structures but not appressoria.

Purpose of the Study:

  • * To compare the formation of appressoria by germ tubes and appressorium-like structures by hyphal tips in M. oryzae.
  • * To investigate the distinct molecular mechanisms governing these two differentiation processes.

Main Methods:

  • * Comparative analysis of appressoria and appressorium-like structures in M. oryzae.
  • * Assessment of structural differences, size, and turgor pressure.
  • * Chemical and surface treatments to induce structure formation.
  • * Analysis of signaling mutants (Osm1, Mps1, Pmk1, cpkA, con7).

Main Results:

  • * Both structures possess a melanin layer, absent in the pore region; appressorium-like structures are larger but have lower turgor pressure.
  • * cAMP, IBMX, and cutin monomers induced appressoria but not appressorium-like structures; waxes induced both.
  • * Pmk1 is essential for both structures, while Osm1 and Mps1 are dispensable.
  • * cpkA mutants showed reduced appressorium-like structure formation, and con7 mutants failed to form appressorium-like structures but retained appressoria formation.

Conclusions:

  • * Appressorium formation by germ tubes and appressorium-like structure development by hyphal tips are distinct differentiation processes in M. oryzae.
  • * These processes involve partially overlapping but also unique molecular mechanisms.

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