A cotyledonary agglutinin from Luetzelburgia auriculata inhibits the fungal growth of Colletotrichum lindemuthianum, Fusarium solani and Aspergillus niger and impairs glucose-stimulated acidification of the incubation medium by Saccharomyces cerevisiae ce

The aim of this study was to test the hypothesis of the involvement of the cotyledonary Lutzelburgia auriculata agglutinin (LAA) in the plant defense against fungi. It was observed that LAA is localized at the periphery of the cotyledon and that it is released to the surrounding medium during seed germination when the plantlet is most vulnerable to phytopathogens. When LAA was included in the culture medium it inhibited the fungal growth of Colletotrichum lindemuthianum, Fusarium solani and Aspergillus niger compared to the same fungi cultured in the absence of LAA. To better understand the mechanism of action of LAA on fungal growth, Saccharomyces cerevisiae was used as a model. LAA reversibly bound to the yeast cells, inhibited its growth and promoted a 60% inhibition of the glucose-stimulated acidification of the incubation medium by S. cerevisiae suggesting its interference on the transport of intracellular protons to the external medium. In conclusion, the data indicate that LAA is possibly involved in the plant defense mechanisms against phytopathogen fungi.