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Published on: August 31, 2015
Melanin synthesis is associated with changes in hyphopodial turgor, permeability, and wall rigidity in gaeumannomyces
N P Money1, T C Caesar-TonThat, B Frederick
1Department of Botany, Miami University, Oxford, Ohio, 45056, USA. moneynp@muohio.edu
Abstract:
Mycelia of Gaeumannomyces graminis var. graminis form large cells called hyphopodia with deeply lobed, melanized walls. Like appressoria produced by other pathogens, hyphopodia develop on hydrophobic surfaces, but it is not clear that hyphopodia function as platforms for host penetration. In appressoria, melanin synthesis is linked to the generation of enormous turgor pressures that provide the necessary force for plant penetration. In the present study, hyphopodial turgor was measured in a wild-type strain of G. graminis var. graminis, a mutant exhibiting constitutive synthesis of melanin (referred to as the dark mutant), and a melanin-deficient strain (thr). These experiments demonstrate that hyphopodia of the wild-type strain generate higher pressures than the dark mutant and that nonmelanized thr hyphopodia generate minuscule internal pressures. Melanization of the wall is also associated with an increase in its rigidity. These data correlate with differences in wall permeability consistent with a recent model for turgor generation by appressoria.
Insights
Melanin synthesis in Gaeumannomyces graminis var. graminis hyphopodia is crucial for generating high turgor pressures and wall rigidity, enabling potential host plant penetration.
Area of Science:
- Plant Pathology
- Mycology
- Biochemistry
Background:
- Hyphopodia, specialized structures of Gaeumannomyces graminis var. graminis, possess melanized walls and form on hydrophobic surfaces.
- The role of hyphopodia in host penetration and the function of melanin in this process remain unclear.
- Melanin in appressoria of other plant pathogens is linked to high turgor pressure generation for host invasion.
Purpose of the Study:
- To investigate the role of melanin in hyphopodial turgor pressure generation and wall properties.
- To compare turgor pressures in wild-type, dark mutant (constitutive melanin synthesis), and melanin-deficient (thr) strains of G. graminis var. graminis.
Main Methods:
- Measurement of hyphopodial turgor pressure in different G. graminis var. graminis strains.
- Assessment of wall properties, including rigidity and permeability, in relation to melanization.
Main Results:
- Wild-type hyphopodia generated higher turgor pressures than the dark mutant.
- Melanin-deficient (thr) hyphopodia exhibited significantly lower internal pressures.
- Melanization correlated with increased wall rigidity and changes in permeability.
Conclusions:
- Melanin synthesis is essential for generating high turgor pressures in G. graminis var. graminis hyphopodia.
- Melanization contributes to wall rigidity, potentially facilitating host plant penetration.
- Findings support a model of turgor generation involving wall properties and permeability.
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