How fungi degrade cell walls

Oeiras, 05.08.2014

Some fungi live on their ability to degrade plant cells walls but not all degradation pathways are known. Now, a group of researchers led by the Applied and Environmental Mycology Labat ITQB demonstrated that fungi can use suberin, a very recalcitrant component of cell walls, as the sole carbon source and have further elucidated how they do it. The work, which also involves a team from IGC, is published in BMC Genomics.

Uncovering how each plant component is degraded is important to understand plant-fungi interactions and how the cycling of nutrients takes place in nature. In addition, degradation pathways may enclose technological potential for biodegradation or for obtaining new added value compounds. But some degradation pathways remain hidden simply because some plant cell wall components are not easily separated from each other. That was the case for suberin up until a few months ago, when ITQB researchers found a new strategy to extract this plant polyester.

Using isolated suberin in suspension, researchers cultured the fungi Aspergillus nidulans, a well know fungi for biologists, for up to 15 days. During this period they followed the pattern of fungal gene expression and recovered the fungal proteins secreted to the culture medium for analysis. These data were complemented with microscopic observations of fungal morphology.

Researchers concluded that Aspergillus nidulans is able to use suberin macromolecules as a carbon source and identified the major suberin degrading enzymes. Initial suberin modification involved hydrolysis and fatty acid oxidation that released long chain fatty acids but the utilization of these fatty acids by the fungi seems to involve new regulatory elements. Researchers further observed that the plant polyester affected strongly the fungus developmental cycle, inducing the expression of genes coding for both general stress responses and autolysis, and stimulated sexual development. All these signs of stress point to suberin as more than a physical protective barrier in plant-fungi interactions.
 

Original article

BMC Genomics, 2014, 15:613. DOI: 10.1186/1471-2164-15-613

Elucidating how the saprophytic fungus Aspergillus nidulans uses the plant polyester suberin as carbon source

Isabel Martins, Diego O Hartmann, Paula C Alves, Celso Martins, Helga Garcia,
Céline C Leclercq, Rui Ferreira, Ji He, Jenny Renaut, Jörg D Becker and
Cristina Silva Pereira