Production of cell wall degrading enzymes and melanin in response to changes in temperature by Lasiodiplodia theobromae
M. PAOLINELLI-ALFONSO (1), R. Hernández-Martínez (1). (1) Center for Scientific Research and Higher Education of Ensenada (CICESE), Ensenada, Mexico
<i>Lasiodiplodia theobromae</i> is a pathogenic fungus of many different plant species. In grapevine, <i>L. theobromae</i> has been reported as the most aggressive pathogen among the Botryosphaeriaceae. It shows preference to warmest regions, and it has been suggested that it does not present an endophytic stage. The aim of this work was to study the production of cell wall degrading enzymes (CWDEs) and melanin production in <i>L. theobromae</i> grown under temperature stress. Fungal mycelial discs were inoculated on Vogel´s salts supplemented with 1% of grapevine wood and incubated at 28 °C. After 2 days, some flasks were exposed to 42 °C or 4 °C for one hour and returned back to 28 °C. At 0, 2, 3 and 4 days, samples were filtered and cell-free extracts as well as mycelia were collected. Biomass, protein, CWDEs (xylanase, pectinase and cellulase) and melanin were quantified. In comparison to cultures kept always at 28 °C, in cultures heat shocked, the amount of proteins increased independently of fungal growth, and a higher activity of CWDEs was observed. At 4 °C only cellulase activity was higher. The amount of melanin in mycelia decreased in both stress treatments, while the melanin content in the extracts increased. There seems to be a correlation between melanin and CWDEs secretion, which requires further elucidation. These results suggest that higher temperatures induce the secretion of CWDEs in <i>L. theobromae</i>, which might be related to its higher impact in warmest areas.
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