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The ethylene biosynthetic pathway in two major postharvest pathogens Penicillium digitatum and Penicillium expansum: in vitro studies

Rosario Torres: IRTA, XaRTA-Postharvest, Edifici Fruitcentre

<div>In contrast to fungi, higher plants produce ethylene from methionine via the 1-aminocyclopropane-1-carboxylic acid (ACC) pathway. Indeed, two main biosynthetic pathways for ethylene production have been reported in microorganisms including fungi and its utilization does not exclusively depend on the pathogen but rather on the conditions how they are grown. In addition, the role of this hormone in the fungal metabolism of many postharvest pathogens is relatively unknown. <em>Penicillium digitatum</em> and <em>Penicillium expansum</em> are considered widespread fungal pathogens of postharvest rots in citrus and pome fruit, respectively, causing considerable fruit losses. Thus, a deeper understanding of fungal ethylene production could help to design potential disease management strategies in the future. This study aimed at gaining further knowledge on the ethylene production capacity and comparing the ethylene biosynthetic pathway in both <em>P. digitatum</em> and <em>P. expansum</em> grown under different <em>in vitro</em> conditions as well as trying to understand the possible role of this hormone on their metabolism. Our results showed that <em>P. digitatum</em> can produce ethylene over multiple growing conditions whereas <em>P. expansum</em> can produce ethylene exclusively through the 2-keto-4-methylthiobutyric acid (KMBA) pathway and under conditions unlikely to occur in vivo. These results led us to hypothesize that the observed variability in the pathogenicity of <em>P. digitatum</em> (a non-host pathogen) and <em>P. expansum</em> (a compatible pathogen) in apples may be related to the ability of the fungi to produce ethylene.</div>