Antifungal potential of secondary metabolites involved in the interaction between citrus pathogens

Abstract

Numerous postharvest diseases have been reported that cause substantial losses of citrus fruits worldwide. Penicillium digitatum is responsible for up to 90% of production losses, and represent a problem for worldwide economy. In order to control phytopathogens, chemical fungicides have been extensively used. Yet, the use of some artificial fungicides cause concerns about environmental risks and fungal resistance. Therefore, studies focusing on new approaches, such as the use of natural products, are getting attention. Co-culture strategy can be applied to discover new bioactive compounds and to understand microbial ecology. Mass Spectrometry Imaging (MSI) was used to screen for potential antifungal metabolites involved in the interaction between Penicillium digitatum and Penicillium citrinum. MSI revealed a chemical warfare between the fungi: two tetrapeptides, deoxycitrinadin A, citrinadin A, chrysogenamide A and tryptoquialanines are produced in the fungi confrontation zone. Antimicrobial assays confirmed the antifungal activity of the investigated metabolites. Also, tryptoquialanines inhibited sporulation of P. citrinum. The fungal metabolites reported here were never described as antimicrobials until this date, demonstrating that co-cultures involving phytopathogens that compete for the same host is a positive strategy to discover new antifungal agents. However, the use of these natural products on the environment, as a safer strategy, needs further investigation. This paper aimed to contribute to the protection of agriculture, considering health and ecological risks.

Phytotoxic tryptoquialanines producedin vivobyPenicillium digitatumare exported in extracellular vesicles

“…We also observed that fungisporin analogues were grouped in this cluster. A fragmentation pattern with typical ions observed at [M + H] + m/z 120.08, m/z 219.15 and m/z 247.14 was previously described for compounds Phe-Val-Val-Phe and Phe-Val-Val-Tyr (19,29,30) (Fig. S5B and S5C).…”

“…These results suggested that tryptoquialanines are involved in the fruit protection against insects that could compete with the fungus for the rotten fruit (18). In co-culture models, it has been observed that P. digitatum tryptoquialanines were present in the confrontation zone with citrus pathogens, suggesting that tryptoquialanines participate in antifungal defense mechanisms that could provide competitive advantages during infection of the citrus host (19).…”

“…The observed signals corresponded, respectively, to tryptoquialanine A (m/z 519. 19 In the molecular networking analysis, each consensus MS/MS spectrum is represented by a node, and all nodes are labeled with their precursor mass. Indole alkaloids produced by P. digitatum were grouped in clusters A and B since they showed similar fragmentation patterns, with typical indole alkaloid fragments observed at [M + H] + m/z 156.07, m/z 197.10 and m/z 213.10 ( Fig.…”

Penicillium italicum: An Underexplored Postharvest Pathogen

“…The most harmful phytopathogenic fungi of oranges are Penicillium digitatum, which causes the green mold disease, responsible for about 90% of post-harvest losses (Costa et al, 2019b;Papoutsis et al, 2019), and Penicillium italicum Wehmer, the causing agent of the blue mold disease. The latter disease develops more slowly, however, it presents higher resistance to cold (Whiteside et al, 1993;Palou et al, 2002;Iqbal et al, 2012Iqbal et al, , 2017 and to low water availability (Plaza et al, 2003), easily spreading and contaminating a greater number of healthy oranges.…”

Metabolomics Analysis of the Peels of Different Colored Citrus Fruits (Citrus reticulata cv. ‘Shatangju’) During the Maturation Period Based on UHPLC-QQQ-MS

“…According to previous research, the pulp properties of impacted fruit are the main research focus, such as the sugar-acid ratio and flavor, and the peels have not been well investigated [6]. Previous studies have shown that metabolites are involved in many biological functions in the development of fruits, such as pigment, antifungal, and antioxidant properties [7][8][9].…”